tag:blogger.com,1999:blog-8962375424093634902024-02-07T03:03:54.496-06:00HWFCI News, Updates & FAQLetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.comBlogger34125tag:blogger.com,1999:blog-896237542409363490.post-36137919202467053082015-01-13T23:22:00.000-06:002015-01-13T23:22:59.905-06:00Plug Power SuppliesI can't believe I've never posted this question before... I receive this email probably once a week and finally realized I don't have the response written anywhere... Arg...<br />
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Almost everyone who emails me wants to use a salvaged plug power supply (cell phone charger, small electronic power supply, etc). The problem with plug supplies is that they only output ONE voltage and their amperage is often capped rather low (usually 1.0-1.5 amps). When used with nichrome wire to cut foam, most will either clip off or burn up as the unit overheats from over current (short circuiting).<br />
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If you're like most of us, you're building your own hot wire foam cutters to save money. While you can save a ridiculous amount of money by making hand cutters and table cutters for both straight and bendable wire cutting, I highly recommend spending a little money on a good bench top power supply like this one (<a href="http://www.circuitspecialists.com/csi3010sw.html" target="_blank">link</a>). It will last you darn near forever and can be used for almost every hobby foam cutter.<br />
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If you want to save additional money on a power supply you can build your own from scratch. Check out my <a href="http://hotwirefoamcutterinfo.com/_DIYPSDesign.html" target="_blank">DIY Power Supply</a> which uses a step down AC transformer from Jacobs-Online. And no, a door bell transformer really won't work either, unless you want to frustrate yourself.<br />
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Between the Jacobs' step down transformer or the Circuit Specialists cheap bench top supply, you'll be purchasing or making a power supply well beyond that of commercially available hot wire foam cutter power supplies at a fraction of the cost.<br />
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Check out the email exchange below, and I'll post as additional replies come along.<br />
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<span style="color: cyan;">Friend, what am I doing wrong?</span></div>
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<span style="color: cyan;">After watching a number of Youtube videos on building foam cutters and reading several different blog articles, I built the table in the "Full Table". </span></div>
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<span style="color: cyan; font-family: Calibri, sans-serif; font-size: 14px;">I purchased the Nichrome 60, 26 gage wire from Jacobs, and soldered the bottom to the transformer cable (Bottom connection photo), and since I want to cut interior holes in foam, I made a "soldered hook" out of the other end of the transformer cable (Top connection photo) and a loop in the Nichrome to attach it (spring tension tight--Top connection photo).</span></div>
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<span style="color: cyan;">I used an old transformer that I had that is rated 12 volts (as recommended--see photos), but when turned on, it does not heat the wire. </span></div>
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<span style="color: cyan;">It is possible that the top loop connection is not completing the circuit, but I suspect the problem is that the transformer is putting out only 1250mA LPS.</span></div>
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<span style="color: cyan;">The cable is only 8 inches long. </span></div>
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<span style="color: cyan;">What do I need to heat it to cutting temperature?</span></div>
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<span style="color: orange;">My pleasure to help, and having worked people through this exact problem multiple times, I see your issue straight away.</span></div>
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<span style="color: orange;">Long story short, your problem is not in the design nor construction of your table top cutter. It looks like you have effectively isolated your circuit and it does not appear to be grounding anywhere. (I couldn’t tell the exact connection of the lower attachment on the eye hook, but I’m assuming you have the connection wire soldered in place too.)</span></div>
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<span style="color: orange;">The issue lies within your power supply but first here is a summary of your circuit ::</span></div>
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<span style="color: orange;">26 gauge NiCr Wire - 2.67 ohms per foot</span></div>
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<span style="color: orange;">8” nichrome length = 1.78 ohms</span></div>
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<span style="color: orange;">Output Voltage = 12 volts</span></div>
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<span style="color: orange;">Max Power Supply Output Amperage = 1.25 amps</span></div>
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<span style="color: orange;">First off, I usually tell people that while 400°F can cut foam but I recommend shooting for 600-800°F just to make it a fast cut. For 26ga NiCr Wire, you will need 2.1 - 2.6 amps to reach 600-800°F respectively.</span></div>
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<span style="color: orange;">Secondly, you need to keep in mind that plug supplies like you have output a CONSTANT 12 volts, and the amperage is a function of your circuits resistance. Meaning.. You are applying 12 volts to your 1.78 ohm circuit.. and with Ohms law you can calculate that yields 6.74 amps!</span></div>
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<span style="color: orange;">Your power supply can only output 1.25amps (or 1250 mA), and cannot handle 6.74 amps. The supply likely has built in over-current-protection or OCP which I discuss here (<a href="http://hotwirefoamcutterinfo.com/OCP_files/OCP.pdf">link</a>). Chances are the power supply is saving itself and simply shutting off, not allowing any current to flow through it. Regardless, even if it was allowed the 1.25 amps to flow, that wouldn’t be enough heat to cut.</span></div>
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<span style="color: orange;">On the <a href="http://hotwirefoamcutterinfo.com/Introduction.html">Introduction page</a>, at the very bottom of the page I have a quick reference cheat sheet for gauges, amperages, and lengths. It’s a quick’n’dirty scale to let you know if your power supply can match up.</span></div>
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<span style="color: orange;">Also, check out our <a href="http://hotwirefoamcutterinfo.com/__SupplyCalc.html">Power Supply Calculation Page</a> which also has a walk-through video on how to calculate your power supply requirements for your project. </span></div>
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<span style="color: orange;">For this cutter, you will be best served by using a variable voltage power supply or bench top power supply. That way you can adjust/fine tune the voltage to achieve an optimal cutting temperature for your application. With you’re current set up, you’re going to need around 3.8-4.6 volts, which will draw 2.1-2.6 amps from your power supply. Granted, you might want your wire hotter than that though as these theoretical calculations do not take into account heat lost to the environment, additional resistance from your electrical attachment, nor heat consumed during cutting. </span></div>
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<span style="color: orange;">It is more likely that you’ll require upwards of 6 volts and 3.4 amps. </span></div>
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<span style="color: orange;">Circuit Specialists have a very cheap bench top power supply. It is a 30 volt 10 amp (<a href="http://www.circuitspecialists.com/i-182253.html">link</a>), variable voltage power supply. You honestly can’t get this kind of power for that little price. This supply also allows you to manipulate either voltage or amperage, which is great. But remember, power supplies ONLY apply voltage to a circuit and then draws amperage based on your circuit’s resistance. So by “controlling” amperage, you are setting what your desired output amperage is and the machine is calculating your necessary voltage to achieve that amperage based on your circuit. So don’t let that dial confuse you. But the supply is a really nice, great functions, and for such a cheap price (comparable models for 2-3 times that).</span></div>
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<span style="color: orange;">If you want to build your own power supply, check out this page (<a href="http://hotwirefoamcutterinfo.com/_DIYPSDesign.html">link</a>). To answer a question ahead of time, a door bell transformer will not work for you either. </span></div>
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<span style="color: orange;">So I hope that explained everything for you! Let me know if you have any additional questions. </span></div>
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LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com2tag:blogger.com,1999:blog-896237542409363490.post-45970064054758578712014-09-04T18:40:00.000-05:002014-09-10T13:47:00.819-05:00Power Supply Convo...<div>
<span style="color: orange;">I guess I'm not sure if I should keep posting these emails or not.. The questions seem to be common and I get them regularly. And I suppose not everyone reads the blog or news section, lol... BUT maybe it will help someone searching the web if the happen upon it. SO, here's another PS question.</span><br />
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<span style="color: cyan;">We need to cut PU Foam having a density of 6 to 7 kg/cu.mtr by using a straight</span></div>
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<span style="color: cyan;">As per suggestions, we have worked out to use a 26 gauge NiCr wire of 2 feet length for a straight wire cutter using a power supply of 12 volt 2 amp.</span></div>
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<span style="color: orange;">I think you should anticipate at least 4 amps.. The 2 amp mark is really a minimum when it comes to cutting foam. Also, try to find a power supply that allows you to adjust the voltage.</span></div>
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<span style="color: orange;">When you start to cut foam, heat exchanges from the wire to your substrate (PUFoam). As the wire cools, it takes time to heat back up to a cutting temperature. In most cases what happens is your cutting speed slows dramatically, and most often will lead to wire breakage as people push harder to cut faster. </span></div>
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<span style="color: orange;">With 3-4 amps you have a hotter wire, that can replenish heat faster, and cut faster without compromising your wire. Ideally the substrate (PUFoam) never actually touches the wire, it is the heat radiating around the wire (the kerf) that actually cuts the foam. </span></div>
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<span style="color: cyan;">Please let us know if we need output voltage as 12v DC or 12v AC.</span></div>
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<span style="color: orange;">AC versus DC, doesn’t matter. It is just important that you have enough current. Try to find a 24v4a variable power supply, and you should be all set!</span></div>
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<span style="color: orange;">Depending on where you’re at in the world, <a href="http://www.mastechpowersupply.com/dc-power-supply/linear-power-supply/mastech-variable-bench-power-supply-30v-5a-hy3005d/prod_3.html">this power supply</a> should suit all your needs and is rated for international use. </span><br />
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<span style="color: cyan;">Thanks for your guidance and are sure that will positively be of immense use to me.</span></div>
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<span style="color: cyan;">I would like to tell you the exact use of hot wire foam cutter which I want to use for commercial</span></div>
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<span style="color: cyan;">purposes to cut low density (ranging from 6 to 7 kg/cu.mtr) PU Foam sheets of thickness varying from 2.5 mm </span><span style="color: cyan;">to 6 mm stacked to a height of about 18 inches (i.e. say 100 sheets of 4.50 mm piled over one another) and cutting </span><span style="color: cyan;">to smaller size sheets of size 8 X 18 inches from bigger sheets of size 32 x 72 inches.</span></div>
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<span style="color: cyan;">So please suggest what type of nichrome wire and power supply would be required for a straight hot wire foam </span><span style="color: cyan;">cutter so that large volumes of the above sheets can be cut.</span></div>
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<span style="color: orange;">It looks like you’re cutting wire will need to be 36” wide to make a comfortable cut. You always want to give a little extra cutting line to make it easier on yourself, but should be able to get everything to line up if you have a standard cutting jig or a stop-board. But I’m sure you can figure that out. </span></div>
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<span style="color: orange;">Polyurethane foam is a little funny when it comes to cutting. Because it is an open cell foam, the little pockets of air between the foam matrix will actually suck up a little heat during your cut. Interestingly enough, the air acts like a little insulator during the cutting process and actually slows things down further.</span></div>
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<span style="color: orange;">At cutting lengths over 24” I tell people it is a good idea to go with 24 gauge nichrome wire. It is a little more stiff and is a little stronger than 26 gauge wire. Plus, the voltage/amperage requirements of 24 gauge is a little easier to deal with than 26 gauge nichrome wire. </span></div>
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<span style="color: orange;">One draw back with nichrome wire at longer distances is that it may be hard to control the wire expansion and line “sag.” I’ve had some wavy cuts with larger cutters, but you can help prevent this by making the wire quite tight with a spring and use a higher temperature. A higher temperature helps less PU foam touch the wire during cutting, and the tight spring helps prevent line sag.</span></div>
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<span style="color: orange;">One other thought would be for you to use/try Rene Wire (<a href="http://jacobs-online.biz/rene_wire.htm#rene2">link</a>). Rene is sort of a “top of the line” cutting wire. It is highly resistant to breaking, won’t have as much line sag, and cuts well for both hobby and industrial purposes. For power supply calculations, 27 gauge Rene wire is similar to 28 gauge Nichrome wire.</span></div>
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<span style="color: orange;">If you want to make your own power supply, I would recommend the <a href="http://jacobs-online.biz/transformers.htm">XFR3018E </a>transformer from Jacobs-online. You’ll have to have a bit of electrical ability, and wire in a dimmer switch. I have a walk-through <a href="http://hotwirefoamcutterinfo.com/_DIYPSDesign.html">tutorial</a> where I use a different transformer, but the <a href="http://hotwirefoamcutterinfo.com/_DIYPSDesign.html">images</a> are essentially the same. </span></div>
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LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-16684576965165983472014-08-30T11:59:00.004-05:002014-08-30T14:36:14.555-05:00AC/DCJust another question on AC or DC power supplies. Seems to be common.<br />
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<span style="font-family: arial, sans, sans-serif;"><span style="background-color: black; color: cyan;">when we say power supply requirement is 12 volt 2 amp .does this mean that we need a power supply to convert 230 volt ac supply to 12 volt dc or ac.</span></span></blockquote>
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<span style="color: orange;">For Nichrome Wire, it doesn’t matter if it is AC or DC. You just want to make sure your power supply has enough power (wattage) to handle the circuit’s current (amperage). I usually tell people that 2 amp is kind of your minimum. If you can find a 4 amp power supply you’ll be able to have a wider range of wire temperatures. </span></div>
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<span style="color: orange;">Also, remember that the voltage is constant and amperage is a function of your wires resistance. So depending on your circuit, and depending on your voltage setting, you may only require 2.5 amps to heat rather than the full power supply’s 4 amps… Just remember voltage is constant, amperage is variable based on wire/circuit resistance</span></div>
LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-33383891546114067212014-08-25T13:58:00.004-05:002014-08-30T12:01:26.401-05:00Kanthal Wire<span style="font-family: ArialMT; font-size: 13px;"><span style="color: cyan;">I am interested to know whether it is possible to use round Kanthal 0.32mm wire as opposed to Nichrome wire in a HWFC?</span></span><br />
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<span style="color: orange;">I don’t see why not? My experience is in Nichrome wire and a little in stainless steel. But when building a simple cutter, you only really need a resistance wire and the alloy shouldn’t really matter. </span></div>
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<span style="color: orange;">I have used and recommend NiChrome because its electrical properties are known and easy to calculate. Most of the other alloys have resistance information but not necessarily amperage-to-heat tables. </span></div>
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<span style="color: orange;">Using Ohms law, with a given wire’s resistance you should be able to calculate an amperage based on applied voltage. So you can see if your power supply has enough juice to handle the circuit. </span></div>
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<span style="color: orange;">Aside from that, I did find a website that has some reference data ( <a href="http://resistancewire.com/resources/alloy-specs">here</a> ). Whenever people ask about novel wire or applications, I always encourage them to give it a try knowing that you can always fall back on nichrome if you need to!</span><br />
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<span style="color: cyan;">Thank for the quick reply. I have done a lot of research in constructing a HWFC's, and of all the websites and YT videos no one seems to have tried Kanthal. So being a bit of an experimenter, I have ordered some Kanthal from a supplier on eBay.</span></div>
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<span style="color: cyan;"> Also I would like to use a 12v 6a supply apapter and regulate the dc output (as opposed to regulating the ac input) with a high amperage dimmer switch that I also saw on eBay.... similar to eBay item number 191295309081 </span></div>
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<span style="color: cyan;">Thanks for the the info from your website, it has been most useful.</span></div>
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<span style="color: cyan;">Perhaps I will make a video of the HWFC I build and post it on YT.</span></div>
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<span style="color: cyan;">Yes, I will let you know the outcome of using Kanthal when I finish constructing my HWFC.</span></div>
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<span style="color: orange;">All that sounds great, I don’t have any additional input just some thoughts. </span></div>
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<span style="color: orange;">In general, you never really want to dim the primary side (AC input) of a transformer. Especially if it is an AC-to-DC power supply. It can have unreliable but also potentially adverse effects on the electrical set up. Even with your AC step down transformers (AC-AC) you want to dim the secondary windings (output side) of the power supply. </span></div>
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<span style="color: orange;">As for that DC dimmer, that is cheap! I’ll have to save that information. I had a user email me some information on a DC dimmer, but they were hard to find. I don’t know why I never thought of a LED strip dimmer…! Thanks for the information. </span></div>
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<span style="color: orange;">I think your set up is going to work well. Having the 6a output on your power supply should be more than enough to amperage to power almost any circuit. You’ll just have to watch out for your circuit’s overall resistance though, as the 12v might not be enough pressure gradient to push current though high resistance circuits. But as always, give it a crack and see if it works!</span></div>
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<span style="color: cyan;">I read your email with great interest - thanks for sending it.</span></div>
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<span style="color: cyan;">I received the Kanthal wire yesterday. I got the 0.32mm 28 AWG Kanthal A1 gauge wire.</span></div>
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<span style="color: cyan;">From this website:</span></div>
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<a href="http://godofsteam.wordpress.com/2013/08/07/resistance-chart-for-kanthal-a1/"><span style="color: cyan;">http://godofsteam.wordpress.com/2013/08/07/resistance-chart-for-kanthal-a1/</span></a></div>
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<span style="color: cyan;">It states that Kanthal A1 for 28 AWG is 0.439 ohms per inch. Now, if I construct a HWFC with about a 24 inch length of wire this should give a resistance of 10.536 ohms (24in x 0.439 ohms). Which if I use a 12v supply the wire should draw (presumably) a maximum of 1.14 Amps (12v ÷ 10.536 ohms) and also presumably the wire should be glowing. Please let me know if my calculations are incorrect or I've overlooked somthing. :)</span></div>
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<span style="color: cyan;">I am still waiting for the dimmer switch and adaptor, hopefully these should arrive soon then I can start construction.</span></div>
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<span style="color: cyan;">I'll let you know what happens...... success or failure!! :D</span></div>
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<span style="color: orange;">All your calculations look correct to me, I’m just not sure about the amperage-to-heat ratio. In the world of NiChrome 1.14 amps really isn’t that much at all. But, if a low amperage like 1.14 can heat up Kanthal enough to glow… it will be a great low amperage alternative to NiChrome. Now you’ve peaked my interest, lol, let me know how it goes.</span></div>
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LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-23694524125599396692014-06-12T21:48:00.001-05:002014-06-12T21:48:47.540-05:00DIY Power SupplyHey All -<br />
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Every few weeks or so, I'll get an email asking about the DIY power supply video and information I provide on my website (<a href="http://hotwirefoamcutterinfo.com/_DIYPSDesign.html" target="_blank">here</a>).<br />
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When Jacobs-Online originally sold their step down transformers, they only had a single input on the primary windings. A few months back (maybe a year), they changed the primary windings to allow for both 120 and 220v input. Thus making the power supplies rated for international use.<br />
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My video only has a walk through for the old style transformer, but the website has all the diagrams necessary to wire the transformer into either 120v input or 220v input.<br />
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I am currently in the process of updating my video to account for this change, which will also include all the new diagrams I have posted on the DIY diagram page.<br />
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I hope this clarifies any questions, although I have a feeling I'll still receive emails until I get the video done... :P<br />
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<br />LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-46678761253593276612014-04-19T15:53:00.001-05:002014-04-19T15:53:16.286-05:00Cold wire...<div class="AppleOriginalContents">
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<span style="text-align: -webkit-auto;"><span style="color: blue;">I recently purchased a Mastech Hy30005D power supply for a Hotwire foam cutter. This unit is working well for lighter 27 gauge wire. However, I need to use heavier 20 gauge wire for detailed shapes, and this unit seems to be under powered for the task. Could you please guide me in a selection? Funds are by no means unlimited, but a need a reliable unit that can provide ample heat to cut at a good pace.,</span></span></blockquote>
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<span style="color: orange;">Just for reference, I'm sure this is the unit you purchased? <a href="http://www.mastechpowersupply.com/dc-power-supply/linear-power-supply/mastech-variable-bench-power-supply-30v-5a-hy3005d/prod_3.html">Link</a></span></div>
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<span style="color: orange;">This unit has a max output of 5amps, which is going to be the source of your problems. </span></div>
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<span style="color: orange;">Let's quick reference the nichrome data chart found on my website - <a href="http://hotwirefoamcutterinfo.com/_NiChromeData_files/NiChrome%20Data_2.pdf">Link</a></span></div>
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<span style="color: orange;">As you'll note, for 20 gauge NiChrome wire, 5 amps will generate just shy of 600°F. But for 27 gauge wire, 5 amps will generate just shy of 1800°F!</span></div>
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<span style="color: orange;">The thing that I've found is wire temperature and cutting speed are related, but often two different things… </span></div>
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<span style="color: orange;">Most styrofoam products will melt at around 400-600°F, so theoretically a 600°F cutting line should suffice for cutting purposes. But remember, heat has to LEAVE your wire, and enter the sytrofoam to melt and cut the substrate. So your wire has to heat BACK UP in order to cut the next section of foam. Often what people will notice is when the wire FIRST touches the styrofoam it will cut REALLY well, then it will slow down as you get more into the cut. This is because the heat has left your wire, and the wire is having a hard time heating back up to match your cutting speed. </span></div>
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<span style="color: orange;">The fix is that you need to send more current through your wire. You need to have a hotter over-all wire, to increase your cutting speed. The heating-cooling-heating process will find a happy medium, you just have to find out what that is…</span></div>
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<span style="color: orange;">For 20 gauge nichrome, 5 amps will work.. albeit a little slow. For some people, considering the cost, a little slower cut might be acceptable if you have a working product as a trade off. </span></div>
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<span style="color: orange;">From a power supply, I think you would want to have the ability to increase your amperage to 7-8 amps, just so you can play around with your final cutting speed. Here are a few options</span></div>
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<span style="color: orange;">30v10a - <a href="http://www.circuitspecialists.com/i-182253.html">Link</a> - $94</span></blockquote>
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<span style="color: orange;">30v10a - <a href="http://www.mastechpowersupply.com/dc-power-supply/linear-power-supply/volteq-regulated-variable-dc-power-supply-hy3010d-30v-10a-new-model/prod_84.html">Link</a> - $170</span></blockquote>
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<span style="color: orange;">18v10a - <a href="http://www.mastechpowersupply.com/dc-power-supply/linear-power-supply/volteq-variable-linear-power-supply-gpr-1810hd-18v-10a/prod_69.html">Link</a> - $140</span></blockquote>
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<span style="color: orange;">Another option would be to select a variac, which is an AC transformer… higher voltage, so be cautious during use</span></div>
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<span style="color: orange;">130v20a - <a href="http://www.circuitspecialists.com/variac-tdgc2-2.html">Link</a> - $109</span></div>
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<span style="color: orange;">130v30a - <a href="http://www.circuitspecialists.com/variac-tdgc-3kva.html">Link</a> - $134</span></div>
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<span style="color: orange;">For the money, I'd select the $94 unit from circuit specialists. It has both a higher voltage (good for small wire) and a higher amperage (good for large wire). </span></div>
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LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-87010778167425581472014-04-18T13:05:00.000-05:002014-04-18T13:05:42.167-05:00Tattoo Power Supply Freak Out<blockquote style="font-family: Arial; orphans: 2; text-align: -webkit-auto; widows: 2;" type="cite">
<span style="color: blue;">I am building a hotwire table. I'm using my tattoo power supply as a source. It's output is fine (3-15-V Dc).Even the clip cord reads the same . When I connect it to the table my voltage goes crazy! So the problem has to be in my table components. Is a "stove" Bolt necessary? Or will any bolt do?</span></blockquote>
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<span style="color: orange;">Any bolt will do fine, but I agree the problem is not necessarily with your power supply.</span></div>
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<span style="color: orange;">So… let's see if I can keep this simple. </span></div>
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<span style="color: orange;">Any time a power supply is placed under an electrical load (your cutter) you will see a small voltage drop at any attached reader. This is a normal result of electrical resistance, current output, etc. </span></div>
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<span style="color: orange;">But your problem is MOST likely related to the maximum output amperage/wattage of your power supply. If the numbers are going all crazy once you hook up your supply, then I'd wager a guess you're "clipping" out the power supply as an over current protection. Or, if there is no OCP, then it could just be feeding back, overloading your power supply and it's shorting out. </span></div>
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<span style="color: orange;">Here is a document I have on OCP - <a href="http://hotwirefoamcutterinfo.com/OCP_files/OCP.pdf">Link</a></span></div>
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<span style="font-family: Arial; orphans: 2; text-align: -webkit-auto; widows: 2;"><span style="color: orange;">While you mentioned your power supply is 3-15v DC, that is not the most important part. You need to determine the maximum safe output amperage and/or the max output wattage. THAT is what tells you the capacity of your power supply. In MOST circumstances tattoo power supplies max out around 2.0 - 2.5 amps, but usually 2.0. Some are only 1.5 amps. The issue is that most hot wire foam cutters, depending on what wire gauge you use, require about 2.5-3.5 amps to heat effectively.</span></span><br />
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<span style="color: orange;">Relating all this back to your cutter.</span></div>
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<span style="color: orange;">Your cutter has a defined resistance, and when an electrical pressure (voltage) is placed on that circuit (cutter) it will generate a current (amperage). If your resistance is too low, and your voltage is too high, it will allow too much current to flow; and that flowing current may be higher than what your power supply can handle. </span></div>
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<span style="color: orange;">Your solution is to use a smaller gauge nichrome wire (which has a higher resistance) or include a resistor in your circuit. I have a tutorial video on making your own resistor out of aluminum wire. </span></div>
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<span style="color: orange;">Check out my Electrical Calculations Videos ( <a href="http://hotwirefoamcutterinfo.com/_ElectricalCalcVideo.html">link</a> ) which should be a really good walk through from beginning to end.</span></div>
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LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-47344961332222773682014-04-14T15:26:00.004-05:002014-04-15T15:28:31.593-05:00Large length CNC cutterAnother email, a user in Malaysia is trying to build a CNC foam cutter. Needed help on a 10 foot cutter… This message starts out already broken up, and with my replies.<br />
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<span style="color: blue;">I live in Malaysia, and our current here is about 240V, i believe.</span></blockquote>
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<span style="color: orange;">Yes, you're right, but not to split hairs :) You're <i style="font-weight: bold;">Voltage</i> is ~220-240v, the <i style="font-weight: bold;">Current</i> will be depend on your circuit. </span></div>
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<span style="color: blue;">I am trying to make a mini hot wire cnc cutter for my small production area, to cut our 8ft x 4ft x 2ft block of 16kg per piece foam. The machine I intend to build is about 10 ft x 5 ft x 4 ft, actual cutting is about the block size. One block at a time, I will need to cut them. I went to your site and saw this, you recommend a gauge 26 straight wire from Jacobs.</span></blockquote>
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<span style="color: orange;">Yes, in general I recommend 26 gauge for straight wire cutting. But 26 gauge isn't necessarily the best choice at lengths greater than 2-3 feet. It is a higher resistance wire, and a lot of the times you then need a higher voltage in order to power it. </span></div>
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<span style="color: orange;">A lot of CNC and Wing cutters have recommended going with a stainless steel wire OR using 27 gauge Rene wire. Jacobs just started carrying 27 gauge Rene wire and <a href="http://www.terminaltackleco.com/">Terminal Tackle</a> has stainless steel leader wire. </span></div>
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<span style="color: orange;">You may find that Rene wire or stainless steel wire allows for a higher tensile strength and allows you to keep your wire tight while cutting. The 26 gauge wire may bow during cutting and/or may snap if you place too high of a pressure while cutting at those lengths.</span> </div>
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<span style="color: blue;">, and with the calculator, I used, it seems to say, at about 5 ft across, using a gauge 26 hot wire at 600F temp, I will need a 28Volts & 2.1Amps.</span></div>
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<span style="color: blue;">However, sometimes, if I change the direction of the plane to 10 ft cuts, it will require 56Volts & 2.1Amps.</span></div>
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<span style="color: blue;">I am running two setups on one machine, in that case, do I use 2 different power supplies with variable voltages & variable amps? or do I just go with something that can cope with two of them, since I only use either one setup at any given time.</span></div>
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<span style="color: orange;">Definitely go with one power supply that can cope with both circuits. The last thing you want to do is switch between power supplies half way in. </span></div>
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<span style="color: orange;">Your calculations are very accurate, and you did a great job. But the ONE thing that most people don't take into account is cutting speed. And that has just as much to do with wire temperature as anything else. </span></div>
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<span style="color: orange;">Technically 600°F is enough heat to melt and cut foam, but as that heat transfers from the wire to the foam your wire is cooled. Then your wire has to heat back up. This is a continuous and ongoing process as you cut foam, and often you will find a "steady state" where heat is leaving your wire and the wire is heating back up. </span></div>
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<span style="color: orange;">As a rough gauge, I like no less than 4 amps pulling through a LONG wire at any given time. While it is a hotter cutting temperature to start out, the total wire temperature will actually decrease once you start cutting. So if you start out calculated and start cutting at 600°F and it cools to 400°F, that is a lot slower cutting than if you start out at 1000°F and it cools to 800°F. Also, at a higher current (4-5 amps) the wire will replenish heat quicker, which means there will be less of a temperature drop than at lower currents. Of course, all theoretical temperature drops, but it illustrates the point. </span></div>
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<span style="color: blue;">also, you said something about adding a 20% on top of this numbers, so I should getting something like 33.6Volts & 2.52Amps for the 1st setup (5ft)? and 67.2Volts & 2.52Amps for the 2nd setup (10ft)?</span></blockquote>
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<span style="color: orange;">Yea, you never want to run a power supply at 100% capacity. You should aim for 80%. You CAN run it at 100%, but that may decrease the life span of your power supply. At 80%, it doesn't have to work as hard. </span></div>
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<span style="color: orange;">If you're interested in building your own variable voltage power supply, Jacobs does have some transformers that would work really well. Here is the <a href="http://jacobs-online.biz/transformers.htm">link</a>. Scroll to the bottom, I'd recommend the XFR-3018e. It would have a wide range of voltages and currents for you to work with. </span></div>
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<span style="color: orange;">Otherwise you might want to consider finding an "AC Step Down Transformer" also known as a "Variac". Those are usually nice units, and good for the price. But not too many are rated for 220V input. They're out there, just have to find them. THis is one unit from Mastech (<a href="http://www.mastechpowersupply.com/variac-auto-transformer/volteq-2kva-transformer-variac-2000va-0-250v-220v-input/prod_32.html">link</a>)</span></div>
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<span style="color: orange;">I hope that answers your questions, and feel free to write back. I'd be happy to help. Also, I just put up a new link from <a href="http://dexmachine.com/">dexmachine.com</a>. They are from Canada and specialize in large scale CNC cutters. You can try to get a hold of them and see what help they can provide too.</span> </div>
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<span style="color: magenta; font-family: arial, sans-serif; font-size: 13px;">You wrote "As a rough gauge, I like no less than 4 amps pulling through a LONG wire at any given time. While it is a hotter cutting temperature to start out, the total wire temperature will actually decrease once you start cutting. So if you start out calculated and start cutting at 600°F and it cools to 400°F, that is a lot slower cutting than if you start out at 1000°F and it cools to 800°F. Also, at a higher current (4-5 amps) the wire will replenish heat quicker, which means there will be less of a temperature drop than at lower currents. Of course, all theoretical temperature drops, but it illustrates the point."</span><br />
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<span style="color: #0061ff;">so, at 56V, 2.1A on a 10ft gauge 26 Nichrome wire. you said that it would be better to start out cutting around 1000F, which means both the V and A are now increased to 86V & 3.2A.</span><br />
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<span style="color: #0061ff;">what I am confused is, do I just UP the Amps, or i still use the calculator for both Volts and Amps INCREASE, as you said maintained no less than 4Amps?</span></div>
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<span style="color: orange;">This is a tricky one to explain, but once you understand it, it will make sense. </span></div>
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<span style="color: orange;">When you are controlling a power supply, typically you can only ever control "voltage" you can not directly control amperage. Your amperage is a function of the applied voltage and circuit resistance…</span></div>
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<span style="color: orange;">However, when you're heating a wire, Amperage (and/or wattage) is what correlates to heat and temperature. </span></div>
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<span style="color: orange;">So when I say I like about 4 amps, thats just a rough gauge based on a desired temperature and cutting speed; I was also only using 1000°F as a generalization as well. In order to obtain 4 amps, the voltage will vary depending on if you're using 26 gauge or if its 16 gauge. </span></div>
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<span style="color: orange;">You calculated correctly, to hit ~1000°F with 10 feet of NiCr 26 gauge, you'll need around 85v and 3.2 amps. </span></div>
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<span style="color: orange;">But again, at such long lengths, you might want to consider stainless steel wire or rene wire.</span> </div>
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<span style="color: blue;">when using bent shapes, i need to go for around gauge 16 ya?</span></blockquote>
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<span style="color: orange;">Yea, that would be about right. Shouldn't need anything thicker. 14 gauge at most.</span></div>
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<span style="color: blue;">In that case, is there any place, you recommend to get 0~20Amps, 0~100Volts variable power supply? @ 220~240V input?</span></blockquote>
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<span style="color: orange;">MastechPowerSupply has this one - <a href="http://www.mastechpowersupply.com/variac-auto-transformer/5kw-transformer-variac-5000va-0-250v-220v-input/prod_30.html">link</a></span></div>
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<span style="color: orange;">It is called a "variac" or step down AC transformer. Much like what is available on jacobs online, but this one is an all-in-one model. You just have to attach your supply lines to the front and then over to your cutting equipment.</span></div>
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<span style="color: orange;">The one tricky thing is that this power supply has a built in voltmeter, not an ammeter. Which.. you're going to care about amperage, not voltage… but functionally won't matter.</span></div>
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<span style="color: blue;">Regarding the cutting speed, i saw many online uses 22inches/sec cutting speed?</span></div>
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<span style="color: blue;">not sure if this is too fast, this is the first time, I'm on this subject, so it will depends if I can figure out everything and do something that speed.</span></div>
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<span style="color: blue;">but just for information, do you think 22"/sec is ok cutting speed, given that I heat it up to 1000F to begin with.</span></div>
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<span style="color: orange;">Honestly I've never heard of 22"/s cutting speed. That is damn fast… are you sure that is the speed?</span></div>
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<span style="color: blue;">the power supply you said, is <b style="font-family: Verdana;">XFR3018E.</b></span></div>
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<span style="color: blue;"><span style="font-family: Verdana;">and the one I saw is </span><b style="font-family: Verdana;">XFR3024E.</b></span></div>
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<span style="color: blue;"><span style="font-family: Verdana;">I am a little confused because, it said:<br />"XFR3018E </span><span style="font-family: Verdana;">is for very large wire gauges of moderate length or very long lengths of medium gauges -- up to 87 inches of 14 gauge or 125 inches of 18 gauge."</span></span></div>
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<span style="font-family: Verdana;"><span style="color: blue;">and</span></span></div>
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<span style="color: blue;"><span style="font-family: Verdana;">"XFR3024E </span><span style="font-family: Verdana;">is for very long medium gauge wire -- up to 102 inches of 16 gauge or 139 inches of 20 gauge."</span></span></div>
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<span style="font-family: Verdana;"><span style="color: blue;"><br /></span></span></div>
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<span style="font-family: Verdana;"><span style="color: blue;">shouldn't XFR3024E be more suitable for my applications since, we also need to bend wires of gauge 16 sometimes to make bowls or domes?</span></span></div>
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<span style="font-family: Verdana;"><span style="color: blue;">just need some explanation of what's the differences and how I should be picking my Power Supply.</span></span></div>
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<span style="color: orange; font-family: Verdana;">Now that I take a second look, I'm not sure either will work. If you go 10 feet with your 26 gauge, you're going to need 86v which neither supply can provide. So…. I think going with the variac from mastech would be best. </span></div>
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<span style="color: blue; font-family: Verdana;">Also, only occasionally that we will use more than 1 hot wire for cutting, so, normally its fine, on a 1-to-1 circuit.</span></div>
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<span style="color: blue; font-family: Verdana;">on that special occasion when we do use 1-to-2 or more, would you recommend parallel or serial circuit to use?</span></div>
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<span style="color: orange;">Well… the easiest thing you can do is run them in series. That would only then change the voltage requirement of your circuit. </span></div>
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<span style="color: orange;">If you place them in parallel, you will change both amperage and voltage. Which… sometimes can be used to your benefit if you want to play around with different types of wire… But parallel circuits just take a bit more calculations. </span></div>
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<span style="color: orange;">If you check out my <a href="http://hotwirefoamcutterinfo.com/__CircuitTheory.html">Circuit Theory page</a>, I go in depth with series and parallel circuits, and what properties change. </span></div>
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<span style="color: orange;">But again… series is just easier as long as your power supply has enough voltage (which that mastech will).</span></div>
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<span style="color: blue;">Nothing to be sorry about. It's all good. I learnt a lot from you and I deeply appreciate your help.</span></div>
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<span style="color: orange;">My pleasure, always glad to help!</span></div>
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<span style="color: blue;">I am considering a dual transformer to perform the required output, but it would seem too wasteful of resources, which I should instead go for the Mastech you talked about.</span></div>
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<span style="color: orange;">Yea, your goal should always be one power supply to handle all circuits. It's not ALWAYS possible, but usually is. It cuts down on supplies, and upstart cost. </span></div>
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<span style="color: blue;">14ga. Wires might be too much for me, so I go ahead with the 16ga. Wires and that should help me with keeping voltage down a little while still keeping the contours of what I need. Normal for dome or bowl shape items only.</span></div>
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<span style="color: blue;">Other long shapes will use the Rene 27ga. Wires to run CNC with.</span></div>
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<span style="color: orange;">Remember that your electrical requirements are opposite for small and large wires. </span></div>
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<span style="color: orange;">Large gauge (16ga) requires less voltage and more amperage.</span></div>
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<span style="color: orange;">Small gauge (26ga) requires more voltage and less amperage. </span></div>
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<span style="color: orange;">So when you're setting your dial on your power supply, always start out at zero and then turn it up until your wire has reached a desirable temperature and cutting speed. </span></div>
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<span style="color: blue;">Speed wise, let me check, might be wrong with 22"/sec. Yes, i am wrong indeed, it should be max 55"/min. NOT per sec. Sorry about the confusion and thanks for the reminder.</span></div>
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<span style="color: orange;">Okay that sounds better…! 22"/second is DAMN FAST, but a 55"/min max is a bit better. That is about 1" per second which is a desirable cutting speed and temperature.</span></div>
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<span style="color: blue;">So confirming the wires, I will need output of max voltage about 100V & max amp about 13A for use with 16ga. (These are with 20% safety buffer)</span></div>
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<span style="color: orange;">Um… sorry, what length of 16 gauge are you using? I lost that in the emails somewhere…</span></div>
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<span style="color: orange;">But if you're applying 100v to 16 gauge and want 13a max, then you're wire has to be 30 feet long… I doubt you'd be using a wire that long?</span></div>
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<span style="color: blue;">So with the Mastech, I no longer need to buy the dimmer, fuse holder, slow blow fuse, and on/off toggle switch?</span></div>
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<span style="color: blue;">Or I still need them, slightly confused, because this is still just a variac transformer? What's else am I missing?</span></div>
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<span style="color: orange;">No, you won't need any of that. It is a completely contained unit. All in one. I'm not 100% sure if it has a fuse or not.. probably does… but either way you probably won't need it. </span></div>
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<span style="color: blue;">I decided to go with the new MasTECH for this one:</span><br />
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<span style="color: blue;"><a href="http://www.mastechpowersupply.com/variac-auto-transformer/5kw-transformer-variac-5000va-0-250v-220v-input/prod_30.html">http://www.mastechpowersupply.com/variac-auto-transformer/5kw-transformer-variac-5000va-0-250v-220v-input/prod_30.html</a></span></div>
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<span style="color: blue;">input 220V</span></div>
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<span style="color: blue;">output 0~250V , 0~20Amps</span></div>
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<span style="color: blue;">USD $168</span></div>
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<span style="color: blue;">I think will be best for all my applications, if one day, I decided to do something larger, I can still work on them without over killing my power unit.</span></div>
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<span style="color: orange;">Yea that is a really nice variac. It has a high amperage, and is nice for you that it has a 220v input. </span></div>
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<span style="color: orange;">Most variacs are strong and withstand a lot of work. I think you'll be happy with that unit for quite some time.</span></div>
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<span style="color: blue;">there's only red and black at the front of the unit, it says IN/OUT, so where do the 3rd ground wire connects to from my outlet?</span></div>
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<span style="color: blue;">still looking at your serial connections.</span></div>
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<span style="color: orange;">These units only have an in and out, they're wired differently than the jacobs-online transformers. These units are essentially fool proof. </span></div>
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<span style="color: orange;">The IN is what comes from your wall, and the OUT is what goes to your cutter. </span></div>
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<span style="color: orange;">On the front of the unit, there is a little brass tab with the universal symbol for "ground".</span></div>
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<span style="color: orange;">This is where you'll want to attach the ground from your wall AND the ground from your cutter. BOth can touch there. If it doesn't fit, there is a screw on the other side that you can attach a wire too as well.. Or just make a jumper with a wire nut. </span><br />
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<span style="color: blue;">still very grateful for all the help I am receiving.</span></div>
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<span style="color: orange;">GLAD TO HELP!!</span><br />
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<span style="color: blue;">I made a little mistake about the 16ga. wires.</span></div>
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<span style="color: blue;">only need about 30V & 11.2A to make it happen, even for the 10ft contours @ 800F.</span></div>
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<span style="color: orange;">That makes more sense :) And yea, you wouldn't need much voltage at all to achieve that amperage and temperature. I bet you'll be happy with the dial set around 30-45 volts.</span></div>
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<span style="color: blue;">for the 27ga. rene wires, it takes about 70V & 2.6A to make it work, and yes its the max 10ft straight line @ 800F.</span></div>
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<span style="color: orange;">Yup, that too looks like a good estimate :)</span></div>
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<span style="color: blue;">the MASTECH 5K will do more than enough for all my applications and at a very reasonable price.</span></div>
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<span style="color: blue;">thanks for recommending MASTECH to me, it solved all my doubts and problems.</span></div>
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<span style="color: orange;">Your welcome. I have really taken a liking to the step down transformers and variacs. They're great for MANY applications and very reasonably priced. When you switch over to the DC world, there is more expense in all the internal components. Functionally, there is no difference between AC and DC circuits when cutting foam.. so go cheap and strong. </span></div>
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<span style="color: blue;">as for you saying measuring the temperature, I saw that you use a Volt and Ampere meter to measure the desired output from the transformer.</span></div>
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<span style="color: blue;">But how do you actually measure the temperature?</span></div>
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<span style="color: orange;">WELLLL often you can't measure temperature. </span></div>
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<span style="color: orange;">I usually only ever measure output amperage, and then reference the nichrome data chart (<a href="http://hotwirefoamcutterinfo.com/_NiChromeData_files/NiChrome%20Data_2.pdf">link</a>) to see where my wire is. It's not the most effective means.. but it is one solution. I've tried an infrared gun before, but I'm not sure it's entirely accurate with such a fine wire. </span></div>
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<span style="color: blue;">As far as I understand that these transformers are we can only adjust the VOLTage on it?</span></div>
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<span style="color: blue;">so if voltage increases what happens to the amperage?</span></div>
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<div class="AppleOriginalContents" style="text-align: -webkit-auto;">
<span style="color: orange;">Voltage directly correlates to amperage, as a function of your circuit's resistance. (Larger gauge, less resistance; smaller gauge, more resistance.)</span></div>
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<span style="color: orange;"><br /></span></div>
<div class="AppleOriginalContents" style="text-align: -webkit-auto;">
<span style="color: orange;">Think of the voltage dial as a kitchen sink faucet handle. If you open the water faucet, it lets out more water because it is allowing more water pressure to escape your pipes. If you turn up the voltage, it lets out more current flow because more electrical pressure is escaping the power supply. Voltage is your pressure, amperage is your flow. Does that make sense?</span></div>
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<span style="color: orange;"><br /></span></div>
<div class="AppleOriginalContents" style="text-align: -webkit-auto;">
<span style="color: orange;">So, in a sense, when you turn up the voltage it too will turn up the amperage. It's just that different amounts of amperage/current will flow depending on your circuits resistance. </span></div>
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<span style="color: orange;"><br /></span></div>
<div class="AppleOriginalContents" style="text-align: -webkit-auto;">
<span style="color: orange;">That's why with large gauge wire, there is less resistance, so it is easier for current to flow. Meaning, it requires less electrical pressure (less voltage) to allow the current to flow.</span></div>
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<span style="color: orange;"><br /></span></div>
<div class="AppleOriginalContents" style="text-align: -webkit-auto;">
<span style="color: orange;">Where as with a small gauge wire, there is more resistance, so it is harder for current to flow. Meaning, it requires more electrical pressure (more voltage) to allow the current to flow. </span></div>
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<span style="color: orange;"><br /></span></div>
<div class="AppleOriginalContents" style="text-align: -webkit-auto;">
<span style="color: orange;">It IS the flowing of electricity that generates your wire heat. And that generation of heat is also in part related to wire resistance. If a wire has more resistance, it is easier to generate heat. Meaning it requires less current flow. If there is less wire resistance, it is harder to generate heat. Meaning it requires more current to flow. </span></div>
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<span style="color: orange;"><br /></span></div>
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<span style="color: orange;">So they're all related….!</span></div>
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<span style="color: blue;">what i am saying is, for the 16ga. wires, we need higher AMP and lower VOLT, so, obviously I can't just go with the lower VOLT on the MASTECH as this will also correspond to the lower AMP?</span></div>
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<span style="color: orange;">I believe I answered this above… but here's my personal theory…</span></div>
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<span style="color: orange;"><br /></span></div>
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<span style="color: orange;">When you are doing calculations manually, it is only to ever help estimate your electrical requirements. Your calculations are supposed to show you which is the BEST power supply to purchase for your application. </span></div>
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<span style="color: orange;"><br /></span></div>
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<span style="color: orange;">BUT… When you get the cutters assembled, and the power supply hooked up. There is always a difference in circuit resistance than what you calculated… THe connectors, the additional wires, the other metal, everything adds to the resistance of your circuit.. even if it's just a little bit. </span></div>
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<span style="color: orange;"><br /></span></div>
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<span style="color: orange;">So, now that you've selected a very good power supply, my recommendation is this.</span></div>
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<span style="color: orange;"><br /></span></div>
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<span style="color: orange;">Hook everything up, with your power supply turned off and starting at "zero". Your calculations will get you to the ballpark of where you need your voltage setting. But essentially you're starting off at zero, and slowly turning up the dial until your wire is cutting at the speed you desire….</span></div>
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<span style="color: orange;"><br /></span></div>
<div class="AppleOriginalContents" style="text-align: -webkit-auto;">
<span style="color: orange;">When you are actually cutting in real life, just start at zero… turn up till its cutting.. and away you go. The theoretical calculations become much less important when it comes time to test the whole thing out.. :)</span></div>
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<span style="color: blue;">there's another question I kept forgetting, but I don't see any serial or parallel wiring that you have in your transformer page?</span></div>
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<span style="color: orange;">Yea, with the mastech there aren't going to be any serial or parallel wirings. There is an input (from the wall) and an output (to your cutter). Basically, the input is your primary windings, and the output is your secondary windings.</span></div>
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<span style="color: orange;"><br /></span></div>
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<span style="color: orange;">The difference is, you're buying a complete package with the Mastech. Everything is all in one, and it's all wired appropriately.</span></div>
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<span style="color: orange;"><br /></span></div>
<div class="AppleOriginalContents" style="text-align: -webkit-auto;">
<span style="color: orange;">When you buy a naked transformer (like on jacobs online), you have to be accountable for wiring in series or parallel, and adding dimmer switches, and mounting brackets… etc etc…</span></div>
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<span style="color: orange;"><br /></span></div>
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<span style="color: orange;">So with that Mastech, it is a complete solution. All you'll need for quite some time… </span></div>
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<span style="color: blue;">I am buying that MASTECH 5K as we speak, will hope to see a good manual on how I can properly use it.</span></div>
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<span style="color: orange;">There should be a manual, lol… I can't imagine there won't be. But again, input(wall) and output(cutter). You will need to make sure you wire the input appropriately (positive and negative terminals), but the output doesn't matter. </span></div>
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<span style="color: orange;"><br /></span></div>
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<span style="color: orange;"><br /></span></div>
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<span style="color: orange;">I hope that all makes sense!!</span></div>
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LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-81285104228798468012014-03-04T00:46:00.001-06:002014-03-06T16:18:57.767-06:00Meters, Power Supply and Wire<br />
Just a back'n'forth with a user via email. I'm in <span style="color: #f6b26b;">orange. </span>This is a really common series of questions I get from people making their own cutters and power supplies. Hope it helps someone out there.<br />
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<span style="color: cyan;">Could I wire in a digital AC voltmeter to output connectors, where cutter plugs into, to see what voltage I'm adjusted to with dimmer?</span></blockquote>
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<span style="color: #e69138;">Yea, you can do that.</span></div>
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<span style="color: #e69138;">If memory serves me correctly… A voltmeter assesses the voltage differential across two points (positive & negative terminals). Therefore essentially being placed in parallel with your circuit. Where as an ammeter assess the flow of electricity through the circuit, needing to be placed in series with your circuit. </span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">The voltmeter should come with instructions for installation, as it might not work if you switch the leads (negative to positive, instead of positive to negative). </span></div>
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<span style="color: cyan;"><span style="-webkit-text-size-adjust: auto;">I made the same power supply as you with the </span><span style="-webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0); font-style: italic; font-weight: 700; text-align: center;">XFR-1006E.</span></span></blockquote>
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<span style="color: #e69138;">Okay, I think you mentioned that previously and I forgot :) </span></div>
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<span style="-webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0); font-style: italic; font-weight: 700; text-align: center;"><br /></span></div>
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<span style="color: cyan;"><span style="-webkit-text-size-adjust: auto;">I purchased the 16 gage wire from Jacobs. Didn't see then u recommended the 20 for rigid cutter like I made. I created one with an adjustable are to use as a straight cutter or rigid, depending on wire. It can adjust from 2 inches up to like 20 inches. </span>Have u used the 16 gage wire with ur same custom power supply? I don't wanna hurt my supply if I don't use right wire to voltage ratio.</span></blockquote>
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<span style="color: #e69138;">Remind me, did you set up your power supply so that you can interchange between 12v/8.3a and 6v/16.7a? If so, then you shouldn't have a problem using the XFR1006e with 16ga.</span></div>
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<a href="http://jacobs-online.biz/assets/xfr1006e-graph.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://jacobs-online.biz/assets/xfr1006e-graph.jpg" /></a></div>
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<span style="color: #e69138;">This diagram shows the acceptable wire gauges and length with the XFR1006e. Just a REALLY rough gauge.. Using the 6 volt setting, and 16 gauge wire, you need to range between about 5" - 25" of workable wire. </span></div>
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<span style="color: cyan;"><span style="-webkit-text-size-adjust: auto;">I looked at Jacobs calculator and it's confusing. Depending what I solve for, it's different I seems. I set temp to 600, gage to 16, choose button to solve for volts and adjusted length for wire. What do you think the min and max of wire I can safely use without burning up transformer. I'm using the same custom power supply as shown on ur site using the </span><span style="background-color: rgba(255, 255, 255, 0); font-style: italic; font-weight: 700;">XFR-1006E</span> transformer.</span></blockquote>
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<span style="color: #e69138;">Check out the <a href="http://hotwirefoamcutterinfo.com/__SupplyCalc.html" target="_blank">Electrical Power page</a>. I have a tutorial video on how to use Jacob's calculator. </span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">Here's what I would do</span></div>
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<span style="color: #e69138;">Set the button to solve for "Temperature"</span></div>
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<span style="color: #e69138;">Move the slide to your wire length, let's say 5"</span></div>
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<span style="color: #e69138;">Set the Gauge to 16</span></div>
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<span style="color: #e69138;"><br /></span></div>
<span class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px; font-family: Helvetica;"><span style="color: #e69138;">Now here's what you're going to look at.</span></span><br />
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<span style="color: #e69138;">As you slide the voltage to the right, you should see the temperature, amperage and wattage change. You'll want to pay attention to the amperage and temperature.</span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">You know that your power supply when set to the 6v setting, can max out at 16.7a. Typically I recommend not exceeding 90% of your power supply's total. But let's just say 16amps. </span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">Moving the voltage slide, you'll see you can not exceed 1.7-1.8 volts before over drawing your power supply. </span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">Next, move the "length" slide to the right, lets choose 10". Slide the voltage, and now you can increase to about 3.4-3.5v before over powering your power supply (~16 amps)</span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">Since you're using a dimmer switch, 100% on is 6 volts.. so 3 volts is half way on… </span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">Does all that make sense? It was a long winded explanation that you can certainly use 16g a with that power supply, it just has to be on the 6v setting. You'll also have to make sure you use AT LEAST 5" of wire, but 10" is probably easier to adjust your power supply with.</span><br />
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<span style="color: cyan;">I haven't got the resistance reading yet. Been trying to think how to calc it. If I knew ohm of circuit, how would I manually calc for max voltage if I don't know any other variables?</span></blockquote>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">If you attach a multimeter and give me the resistance reading, in addition to what gauge nichrome you used, I'll send you a range of working voltages. </span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">Ohms Law states</span></div>
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<span style="color: #e69138;">Voltage = Amperage * Resistance</span></blockquote>
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<span style="color: #e69138;">Amperage is essentially an equivalent of Temperature when using NiChrome wire. </span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">Select a temperature, find it's corresponding amperage, and multiply it times your circuit resistance.</span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">Here is a <a href="http://hotwirefoamcutterinfo.com/_NiChromeData_files/NiChrome%20Data_2.pdf" target="_blank">PDF</a> found on the website with relevant NiChrome Data</span></div>
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<span style="color: cyan;">Ok, but I still want to learn how to calculate </span></div>
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<span style="color: cyan;">Using 16G = 8.7amps @ 600 deg<br /><br />Do I take my length of cutter and divide it by 12 and then multiply that by my meter reading to get R?</span></div>
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<span style="color: cyan;"><br /></span></div>
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<span style="color: cyan;">Then multiply that R by 8.7 amps to get max V?</span></div>
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<span style="color: #e69138;">Short answer, yes!</span></div>
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<span style="color: #e69138;">Long answer...</span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">Your meter reading IS the circuit resistance. You don't have to worry about measuring and dividing anything. Any math related to resistance calculation is only ever theoretical resistances. But if you have a multimeter, set to read resistance (ohms) then there you have it. Total circuit resistance.</span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">Take that reading (<i>my guess is it will be less than 1 ohm</i>) and multiply by 8.7 to yield your power supply voltage setting to reach 8.7amps. Using the 6v power supply setting, your MAX output amps using the <a href="http://jacobs-online.biz/transformers.htm" target="_blank">XFR1006E</a> is ~16a. So if you want to find your MAX volts, just take the resistance reading and multiply by 16. </span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">In my experience, your calculated voltages/amperages/resistances are always a little different than what is seen in person. So just be prepared for about a 10% difference. Not that it will matter for cutting, but just incase you get really specific and want your readings to match your calculations. </span></div>
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<span style="color: cyan;">Used 15 inches of 16Gage and measured 0.50 ohms</span></div>
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<span style="color: #e69138;">Voltage = Amperage * Resistance</span></div>
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<span style="color: #e69138;">600°F</span></div>
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<span style="color: #e69138;">V = 8.7amps * 0.5ohms</span></div>
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<span style="color: #e69138;">V = ~4.4v</span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">800°F</span></div>
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<span style="color: #e69138;">V = 12amps * 0.5ohms</span></div>
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<span style="color: #e69138;">V = 6v</span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">So…</span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">If you used the calculator and only ever looked at theoretical values… 15" of 16 gauge nichrome is only 0.32 ohms. But with all the other metal components, you picked up a little resistance and totaled out at 0.5 ohms. At this point, the only thing that matters is the 0.5 ohms, and no longer the theoretical 0.32 ohms of your 15" NiChrome wire. </span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">From here on out, using that exact set up and knowing that you have 0.5 ohms… whatever amperage you want to achieve, just half the voltage. Want 2 amps? Set 1 volt. Want 8 amps? Set 4 volts. So on and so forth.</span></div>
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<span style="color: cyan;">It all changes if I use shorter or longer wire though, right?</span></div>
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<span style="color: #e69138;">yup</span></div>
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<span style="color: #e69138;"><br /></span></div>
<div style="font-family: Arial; orphans: 2; text-align: -webkit-auto; widows: 2;">
<span style="color: #e69138;">whatever your measured resistance is (based on length of wire) you can plug it into ohms law.</span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">Volts = Amps * Resistance</span></div>
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<span style="color: #e69138;"><br /></span></div>
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<span style="color: #e69138;">Amps = Volts / Resistance</span></div>
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<span style="color: #e69138; font-family: Arial;">Both equations work for whatever you may be doing</span><span style="color: #e69138; font-family: Arial;">…</span><br />
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<span style="color: cyan;">Ok. Think I can do it now. Only other question was I see with the chart is the 600 deg with 26 gage was 8.7amps. The 800 deg shows 10.9 amps. How did u get 12amps for the 800 deg you sent me?</span></blockquote>
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<span style="color: #e69138;">This is that fudge factor I was talking about. You're starting to get too literal between theoretical, calculated and actual temperatures. </span></div>
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<span style="color: #e69138;">Technically 12 amps, with 16 gauge wire, is theoretically 880°F. That temperature is provided by the jacobs calculator. </span></div>
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<span style="color: #e69138;">But again, in my experience, that which is calculated is different than what is seen on your bench. Not to mention, as the foam sucks heat away from your wire, the wire will cool and often slow cutting. So it's a fine balance between wire heat, wire transfer, wire recovery (getting hot) and foam cutting speed. </span></div>
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<span style="color: #e69138;">The calculations are merely so you select a power supply strong enough to supply your circuit. Then get everything on your bench, and turn up the dial until it cuts foam.</span><br />
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<span style="color: cyan;">I see. Are ammeters accurate? Could you attatch it over one wire to make sure you never overdraw Amps that could harm transformer? Do you test it before / input or after / output on transformer?</span></blockquote>
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<span style="color: #e69138;">Yea you should be able to add in an Ammeter. I think the AC ammeters are expensive though. </span></div>
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<span style="color: #e69138;">You would want to attach it to one of your "secondary wires" which are the after/output side of the transformer. You can make it easy though, and simply attach the ammeter to the terminals where your foam cutters plug into the power supply. That way you always get an accurate reading, regardless of which power supply circuit you have activated.</span></div>
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LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-45736073296539709652014-03-01T15:31:00.001-06:002014-03-04T03:28:56.252-06:00Large Multicutter Design<div style="font-family: Arial; orphans: 2; text-align: -webkit-auto; widows: 2;">
Another fairly common question, large multi cutter design</div>
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<span style="background-color: black; font-family: arial, sans, sans-serif; font-size: 13px;"><span style="color: cyan;">I'm planning to build a prototype for a large foam block multi-wire slicer.</span></span></blockquote>
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<span style="background-color: black; font-family: arial, sans, sans-serif; font-size: 13px;"><span style="color: cyan;">Scenario:</span></span></blockquote>
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<span style="background-color: black; font-family: arial, sans, sans-serif; font-size: 13px;"><span style="color: cyan;">1. I will need 5-8 wires</span></span></blockquote>
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<span style="background-color: black; font-family: arial, sans, sans-serif; font-size: 13px;"><span style="color: cyan;">2. The length of the NiChr are going to be 8-9 feet in length</span></span></blockquote>
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<span style="background-color: black; font-family: arial, sans, sans-serif; font-size: 13px;"><span style="color: cyan;">3. I will be cutting different densities of foam, 1lb to 3lb</span></span></blockquote>
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<span style="background-color: black; font-family: arial, sans, sans-serif; font-size: 13px;"><span style="color: cyan;">4. I will be using 220V power</span></span></blockquote>
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<span style="background-color: black; font-family: arial, sans, sans-serif; font-size: 13px;"><span style="color: cyan;">What do yo recommend in this situation?</span></span></blockquote>
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<span style="color: #f6b26b;">With a cutter that large, there are going to be a few difficulties.</span></div>
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<span style="color: #f6b26b;">1. Power Supply</span></blockquote>
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<span style="color: #f6b26b;">2. Wire Tension</span></blockquote>
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<b><u><i><span style="color: #f6b26b;">1. Power Supply</span></i></u></b></div>
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<span style="color: #f6b26b;">The size and power of your power supply will solely depend upon the wire you choose and the overall resistance of your circuit. Over those lengths, I'm not sure that NiChrome wire is going to be your best option. You may want to consider stainless steel wire.</span></div>
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<span style="color: #f6b26b;">The biggest factor with resistance and necessary amperage to heat your wire, is how you lay out your design. If you go with stainless steel wire, chances are you're going to want to set up your wires in circuit series, rather than parallel. But if you use NiChrome wire, you'll probably want to use a combination of series and parallel to achieve the best combination of voltage and amperage requirements. </span></div>
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<span style="color: #f6b26b;">This is discussed in further detail on the website, and should help explain that recommendation a bit more.</span></div>
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<a href="http://hotwirefoamcutterinfo.com/_MultiWireCalc.html"><span style="color: #f6b26b;">http://hotwirefoamcutterinfo.com/_MultiWireCalc.html</span></a></blockquote>
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<span style="color: #f6b26b;">Don't even both trying to find a DC power supply. For something like this an AC Step Down Transformer is going to be your cheapest option for overall output power. If you're using 220v power, I'd assume you're not in the US? If so, I do not have a ton of international options for power supplies. But feel free to scan through my power supply section for some US suppliers that can ship to you.</span></div>
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<a href="http://hotwirefoamcutterinfo.com/___BenchTop.html"><span style="color: #f6b26b;">http://hotwirefoamcutterinfo.com/___BenchTop.html</span></a></blockquote>
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<b><i><u><span style="color: #f6b26b;">2. Wire Tension</span></u></i></b></div>
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<span style="color: #f6b26b;">For lengths over 24" I typically recommend using 24 gauge NiChrome wire. But if you're looking at 8-9 feet, you're going to need something quite strong that will respond to both the pressure of cutting as well as the linear applied wire tension. I still think stainless steel wire is going to be your best option, but I do not have an idea of wire size. Good news is stainless steel wire is cheap, so buy a few rolls and see what gauge wire works best for your design. Keeping in mind that wire gauge and length have a bearing on circuit resistance, and require amperage to heat. You're going to want to find the smallest gauge wire, that can hold up to cutting pressure. Probably 24-18 gauge.</span></div>
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<span style="color: #f6b26b;">Next, I'd recommend designing your cutter so that at one end you have a rigid <i>extension spring</i> and at the other end some type of winding device. Even if that winding device is just an eye bolt you turn to increase wire tension. Keep in mind that as a wire is heated it will expand, and with expansion comes a saggy wire. If you're cutting a grid out of large foam billets, the last thing you want is wavy lines. I suppose it all depends on your application, but you're going to want wire tension. I have actually seen a design were someone used a FULLY threaded pipe, from end to end. And all they had to do was twist the entire pipe, and it increased resistance on all the wires. It was basically a huge, large diameter machine screw at that point. Simplistic design, just requires you to know someone who can thread pipe. </span><br />
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<span class="Apple-style-span" style="-webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; border-collapse: separate; font-family: Helvetica; font-size: small; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px;"><span style="color: cyan;"><div>
I’m thinking of using the Transformer from MastechPowerSupply.</div>
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Volteq 5KW Transformer Variac 5000VA 0-250V 220V Input, with maximum current output of 20amps (@250V)</div>
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or do think I can get away with….</div>
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Volteq 2KW Transformer Variac 2000VA 0-250V 220V Input, with maximum current output of 8amps (@250V)</div>
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<span style="color: #f1c232;">Not just because I'm American.. but I'd have to say "bigger is better." When it comes to non hobby large scale cutters, especially unique set ups, you do NOT want to be 100% ready to go and have an inadequate power supply. With the 5kW unit, you have the same voltage regulation on the dial but have 2.5 times the power. Using the 5kW model, you'll have the best power supply, just in case you need to wire in series on the fly...</span></div>
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<span style="color: #f1c232;">Just remember… Greater than 45 dry volts will penetrate human skin. If you're moving 5kW across something like that… there is a pretty high risk of shock. Just be incredibly careful. </span></div>
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<span class="Apple-style-span" style="-webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; border-collapse: separate; font-family: Helvetica; font-size: small; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px;"><span style="color: cyan;">I’m also thinking of having them wired is Parallel setup, just so I can hook them up on two shafts, and have adjustability on the thickness of the slices, just by moving the Springs up and down along the shafts.</span></span></blockquote>
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<span style="color: #f1c232;">I love the idea, and would love to see it in action. Send some pictures when you get it set up. </span></div>
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<span style="color: #f1c232;">Just remember your electrical properties when placing a circuit in parallel. An easy way to think of it is like this….</span></div>
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<span style="color: #f1c232;">Placing four wire in series, is like making one wire four times as long</span></div>
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<span style="color: #f1c232;">Placing four wires in parallel is like making one wire four times as thick</span></div>
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<span style="color: #f1c232;">When you have a long wire or wires placed in series, the resistance dramatically increases, the voltage required to heat dramatically increases, but the amperage pretty much stays the same. </span></div>
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<span style="color: #f1c232;"><br /></span></div>
<span style="color: #f1c232;">When you have a larger gauge wire or have wires placed in parallel, the resistance dramatically decreases, the required voltage decreases but the necessary amperage to heat the wires dramatically increases. </span><div class="AppleOriginalContents">
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<span style="color: #f1c232;">I hope that wasn't confusing. </span></div>
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<span style="color: #f1c232;">Long story short… depending on how this pans out, you may end up needing a combination of series and parallel to find the right combination of circuit resistance, voltage and amperage. You may even consider having switches to "activate" a cutting line. You'll want something rated at 20amp max, which is usually a house circuit switch.</span></div>
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The majority of the time, I’ll be using one wire, but I want to make sure that I can do 5-7 wires without any issues.</div>
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With the Transformers I have listed above, what do you think there limits are as far as the number of 8-foot wires they can handle? We’ve been using two sizes of wire, 0.010” and 0.014”, in 8-foot lengths for many of our cuts, usually lettering and shapes, so we need smaller wire gauge. Do you think that Stainless Steel is better to use that NiChrome?… with the wire gauges we are using, 30 AWG and 27 AWG, which one would be best for heat and length? Right now we have it automated to cut at around 45in/min on 1 lb density foam.</div>
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<span style="color: #f1c232;">Well… There are a few ways to answer. </span></div>
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<span style="color: #f1c232;">For lengths greater than 2-3' I typically tell people to shy away from NiChrome. Its a good wire, don't get me wrong. But often the resistance is too high at those lengths. Where as, for a small cutter <2' I exclusively recommend NiCHrome wire and NOT stainless steel because NiCr's resistance is higher and makes power supply selection easier. So both are good options, it just depends on your application. </span></div>
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<span style="color: #f1c232;">BUT… </span></div>
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<span style="color: #f1c232;">Jacobs-online.biz JUST started to carry 27 gauge Rene wire…. I think you might like this… Rene wire is considered a super alloy, and virtually indestructible. It is an "up and comer" in the foam cutting world, and a lot of guys use it to cut large (8') foam wings. You might like it a lot, I know Gary Jacobs really likes it. Personally, I am looking into using it for my combination foam cutter as a good straight wire cutter. </span></div>
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<span style="color: #f1c232;">27 gauge Rene wire has similar electrical properties to 28 gauge NiChrome wire, so you can use that reference for calculations. As you would imagine, high wire resistance will be counteracted when placed in parallel. </span></div>
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<span style="color: #f1c232;">Just for kicks, lets see what we can do with a little math. </span></div>
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<span style="color: #f1c232;">A single 8' length of rene (34ohms) would take about 150 volts to heat to 1800° and only draw about <b>4.5</b> amps from your power supply. If you put six 8' lengths of rene wire in parallel (5.667 ohms), my guess would be it's similar to 20 gauge based on length and resistance. Here's the difference… you'd require about 80 volts to heat to 1800° but drawing close to <b>15</b> amps from the power supply.</span> </div>
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LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-8408437312018638902014-02-19T11:20:00.005-06:002014-02-20T22:09:49.700-06:00Very small cutter<span style="background-color: black; color: white;">This question came through YouTube, in response to my combination foam cutter</span><br />
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<span style="font-family: arial, sans-serif; line-height: 17px;"><span style="color: cyan;">I am just curious, why aren't these cutters made to be a little smaller and more manageable...something like a little wire that is shaped like a U where the loop is like 1/32" so you can carve intricate stuff, or a cutter that is several inches long, shaped like an F with the wire going between the short lines of the F, where the wire itself is only 3" or so long?? For me, working at the end of that huge thing would be impossible;/</span></span></span><br />
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<span style="color: #ffd966;"><span style="font-family: arial, sans-serif; line-height: 18px;">You can make cutters as small as you want, this is just an all-in-one prototype that I came up with. It is a work in progress, and I am moving forward with commercial fabrication. But more on that later.</span><br /><br style="font-family: arial, sans-serif; line-height: 18px;" /><span style="font-family: arial, sans-serif; line-height: 18px;">Long story short, when it comes to a hot wire foam cutter, you're electrical requirements are a function of wire diameter/thickness and wire length. With a bendable wire, you cannot use smaller than 20 gauge wire. That size wire requires about 4-6 amps to become hot enough to cut foam. However, a large gauge wire has little resistance, and at 1/32" length, the maximum applied voltage would be incredibly low. In fact, you could not apply more than 0.007 volts to the circuit before overcoming 6 amps. There are virtually no commercially available power supplies that can micro-control voltage that low.</span><br style="font-family: arial, sans-serif; line-height: 18px;" /><br style="font-family: arial, sans-serif; line-height: 18px;" /><span style="font-family: arial, sans-serif; line-height: 18px;">The solution would be to add a resistor to your circuit, to raise the overall circuit resistance. The best case scenario would be finding a variable voltage power supply, that can out put at least 10 amps. You'd have to find a 1 ohm / 50 watt resistor, and place it in-line with your 1/32" 20ga cutter. Your optimal cutting settings would be ~6 volts, drawing 6 amps from your power supply (36 watts), and not overloading the wattage of your resistor (50 watt max).</span></span></span><br />
<span style="background-color: black;"><span style="color: #ffd966;"><span style="font-family: arial, sans-serif; line-height: 18px;"><br /></span></span>
<span style="color: #ffd966; font-family: arial, sans-serif;"><span style="line-height: 18px;">A very small cutter is definitely an option with the right tools and electrical supplies. But small resistors that can handle that level of heat dissipation (wattage) are hard to come by. In most circumstances you have to buy them in bulk. That said… I THINK I have 1ohm 50watt resistors in my shop.. I'd just have to look.</span></span></span><br />
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<span style="color: cyan;"><span style="font-family: arial, sans-serif; line-height: 17px;">Wow......man how can something so simple be so complicated:) Hey does cutting foam with a hot wire give off any fumes?</span><br style="font-family: arial, sans-serif; line-height: 17px;" /><br style="font-family: arial, sans-serif; line-height: 17px;" /><span style="font-family: arial, sans-serif; line-height: 17px;">Thanks for your response, that was very thoughtful of you</span></span></span><br />
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<span style="color: #ffd966;"><span style="font-family: arial, sans-serif; line-height: 18px;">I know!! It is both simple and complex at the same time!</span><br style="font-family: arial, sans-serif; line-height: 18px;" /><br style="font-family: arial, sans-serif; line-height: 18px;" /><span style="font-family: arial, sans-serif; line-height: 18px;">Yes, cutting foam will emit fumes depending on the temperature of your wire. It is a bit of a trade off… A hot wire lets you cut faster but will emit more fumes but a cold wire will cut slower with less fumes. When you have a cold wire, you have to apply more pressure to cut the foam which will increase your chances of breaking the wire. A hot wire usually won't touch the foam because the radiant heat will melt the foam at a distance. Although, the hot wire will cut away more foam (a larger kerf) so sometimes your fine work is lost. Like I said… it's all a series of trade offs. It's a fine balance between temperature, cutting speed, fumes emitted and cutting kerf. </span><br style="font-family: arial, sans-serif; line-height: 18px;" /><br style="font-family: arial, sans-serif; line-height: 18px;" /><span style="font-family: arial, sans-serif; line-height: 18px;">I hope that doesn't overcomplicate!!</span></span></span><br />
<span style="background-color: black;"><span style="color: #ffd966; font-family: arial, sans-serif; font-size: x-small;"><span style="line-height: 18px;"><br /></span></span></span>LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-59585708945923606452014-02-12T23:54:00.000-06:002014-02-12T23:54:21.380-06:0020" Cutter<div>
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<span style="color: cyan;">I need is kind a large cutter which has the dimension more than 20", basically 0.3m or 0.45m would be the best. So would it be possible for you to make one and how much would it be</span></div>
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<span style="color: orange;">Check out this <a href="http://hotwirefoamcutterinfo.com/_LargeHandDesign.html">link</a>, these cutters are really easy to make and all parts should be available at your local hardware store. </span></div>
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<span style="color: orange;">( <a href="http://hotwirefoamcutterinfo.com/_LargeHandDesign.html">http://hotwirefoamcutterinfo.com/_LargeHandDesign.html</a> )</span></div>
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<span class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px; font-family: Helvetica;"><span style="color: orange;">That is going to be your best bet at a practical design for any cutter over 12"/30cm.</span></span><br />
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<span style="color: orange;">I would also suggest that you use 24 gauge nichrome wire, available through <a href="http://www.jacobs-online.biz/nichrome_wire.htm">Jacobs online</a></span></div>
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<span style="color: orange;">( <a href="http://www.jacobs-online.biz/nichrome_wire.htm">http://www.jacobs-online.biz/nichrome_wire.htm</a> )</span></div>
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<span class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px; font-family: Helvetica;"><span style="color: orange;">You will need between 10-12 volts, and 3.5-4.5 amps. Here are a few options</span></span><br />
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<span style="color: orange;">- Option 1 - <a href="http://www.mastechpowersupply.com/dc-power-supply/linear-power-supply/mastech-variable-bench-power-supply-30v-5a-hy3005d/prod_3.html">30volt 5amp</a></span></div>
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<span style="color: orange;">- Option 2 - <a href="http://www.circuitspecialists.com/csi3005sm.html">30volt 5amp</a></span></div>
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<span style="color: orange;">- Option 3 - <a href="http://www.powersupplydepot.com/productview.asp?product=9603+PS">30volt 5amp</a></span></div>
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<span style="color: orange;">If you're still interested in me making you a hot wire foam cutter, we can discuss cost of shipping and production. </span></div>
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LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-17154535846669848172014-02-03T22:17:00.001-06:002014-02-03T22:17:51.032-06:00Beefy 16g Cutter with a battery?<br />
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<span style="background-color: black; color: cyan;"><span style="font-family: arial, sans, sans-serif; font-size: 13px;">I have a quick question for you, how long can I run 16 AWG nichrome wire for continuously off of a battery? The Nichrome wire is 8" each piece run in series. </span><br style="font-family: arial, sans, sans-serif; font-size: 13px;" /><br style="font-family: arial, sans, sans-serif; font-size: 13px;" /><span style="font-family: arial, sans, sans-serif; font-size: 13px;">I was using a 18v drill battery and a 12v motorcycle battery and had horrible results. Both setups melted the wire I was using that was connected to the power source. Whenever I managed to power the nichrome wire I wasn't able to get a long run time before the battery would die, maximum run time was about 1 minute for the motorcycle battery and approximately 30 seconds with the 18v battery. </span><br style="font-family: arial, sans, sans-serif; font-size: 13px;" /><br style="font-family: arial, sans, sans-serif; font-size: 13px;" /><span style="font-family: arial, sans, sans-serif; font-size: 13px;">Thanks for your response in advance.</span></span></blockquote>
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<span style="color: #ffd966;">I sure have been getting a ton of battery questions lately… weird!</span></div>
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<span style="color: #ffd966;">Thank you for your praise of the site, and enjoying its content. It has grown quite vast over the last few years, and some of the information is hard to find. I'm not sure if you found this page, but I have a WHOLE page dedicated to battery power - <a href="http://hotwirefoamcutterinfo.com/__FixedVoltageCalc.html">Link</a> ( <a href="http://hotwirefoamcutterinfo.com/__FixedVoltageCalc.html">http://hotwirefoamcutterinfo.com/__FixedVoltageCalc.html</a> )</span></div>
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<span style="color: #ffd966;">There are a few problems with battery powered circuits…</span></div>
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<b><i><u><span style="color: #ffd966;">Problem 1 - Fixed Voltage</span></u></i></b></div>
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<span style="color: #ffd966;">First and foremost, they are a fixed voltage power supply. Obviously, meaning that they will always output their rated voltage - i.e. 12v, 18v, etc. What you've done with the 12v & 18v batteries is short circuited them both. It's probably good that the wire melted, if they'd have run for a longer duration of time, they'd probably have heated up and exploded.</span></div>
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<span style="color: #ffd966;">16 gauge nichrome, at 8 inches, is approximately 0.173 ohms of resistance. Ohms law states that Amperage or Current is equal to Voltage divided by Resistance… A=V/R</span></div>
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<span style="color: #ffd966;">A = 12v / 0.173o<span class="Apple-tab-span" style="white-space: pre;"> </span>A = 18v / 0.173o</span></div>
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<span style="color: #ffd966;">A = 69.3 amps<span class="Apple-tab-span" style="white-space: pre;"> </span>A = 104.0 amps</span></div>
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<span style="color: #ffd966;">That is some SERIOUS current pulled from those batteries. They'll die extremely quickly and/or heat up extremely quickly which is incredibly unsafe. </span></div>
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<b><i><u><span style="color: #ffd966;">Problem 2 - Available Amperage</span></u></i></b></div>
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<span style="color: #ffd966;">Not every battery is designed to output amperages necessary to cut nichrome wire. There are internal resistances which restrict output amperage from a batter. Also, as a battery heats up, its internal resistance goes up, which also decreases output amperage. Ask any construction contractor who tries to use battery powered tools left in the sun on a HOT summer day. Their battery life is noticeably reduced. </span></div>
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<span style="color: #ffd966;">As a rough gauge, we say that you should not draw more than 1/10th of the Amp-hour (Ah) Rating of your battery. You'll notice the Ah or mAh listed somewhere on your battery.</span></div>
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<span style="color: #ffd966;">So if you have a 20 amp-hour battery, it really should not output more than 2 amps for maximum efficiency.</span></div>
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<b><i><u><span style="color: #ffd966;">Solution</span></u></i></b></div>
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<span style="color: #ffd966;">Unfortunately there probably isn't an effective battery option for 16 gauge nichrome wire. It's liner foot resistance is far too low, and its current-to-heat demands are far too high. </span></div>
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<span style="color: #ffd966;">If you plan on using your 8" cutter to cut foam, I would recommend no less than 8-10 amps of current, which is about 1.4-1.8 amps. </span></div>
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<span style="color: #ffd966;">Jacobs-online.biz has a bunch of really effective and inexpensive AC step-down transformers that you can use to power your beefy 16g 8" cutter. Check them out, you'll be happy you did. </span></div>
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<span style="color: #ffd966;">I hope that answers your questions, but dive into the battery page for a lengthy explanation, and don't be afraid to ask more questions if you have them!</span></div>
LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-24526894204404873622014-01-24T14:05:00.002-06:002014-01-24T14:06:54.570-06:00Common Battery Question<div>
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<span style="color: cyan;">q about hotwire =) can i use a 18650 battery to run this thing instead of plugging in the wall….maybe add a momentary switch??? thanks in advance…</span></blockquote>
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<span style="color: orange;">I'm not entirely sure what a 18650 battery is, I'm assuming it's a 3.7v Lithium Ion battery? In that case, the short answer is no, it won't really work.</span></div>
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<span style="color: orange;">I have a whole section dedicated to fixed voltage power supplies and batteries. Check out this <a href="http://hotwirefoamcutterinfo.com/__FixedVoltageCalc.html">link</a>.</span></div>
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<span style="color: orange;">The problem with batteries is that they are a fixed voltage power source, so you can only regulate your wire temperature by adding a resistor or altering wire length. The second, is that not every battery can withstand or is designed to output currents/amps necessary to heat nichrome wire. With most NiCr wires requiring ~3-4 amps to cut effectively, it is typically not possible with most batteries.</span></div>
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<span style="color: orange;">I do have a few battery sources listed on my website as well. <a href="http://hotwirefoamcutterinfo.com/__Battery.html">Linked here.</a> Again, the problem is fixed voltage. You'll only be able to moderate wire temperature by changing the wire length. That may or may not work for you and your design!</span></div>
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LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-31432031075919147522013-04-17T13:50:00.000-05:002013-04-17T20:57:33.826-05:00Foam Billets<br />
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Just another email I thought I'd post.</div>
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I've been getting a handful of emails recently asking how to cut off sections from foam billets - large rectangular foam blocks. Figured this response would be worth posting. </div>
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User in <span style="color: cyan;">Blue</span>, I'm in <span style="color: orange;">Orange</span>.</div>
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I'll post more if the reply back from the user has some interesting twists.</div>
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-carlo</div>
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<span style="color: cyan;">I was wondering if you have anything that will cut large dense foam block or if you could suggest what i may need to do so</span></div>
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<span style="color: cyan;">The blocks are 4 feet by 30 inches and 8 feet long.</span></div>
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<span style="color: orange;">They call these billets, right? I've had a few people with that same question in the last few months.</span></div>
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<span style="color: orange;">On what dimension are you cutting them? Obviously you'll need to have wire either 30" long, 4' long or 8' long..?</span></div>
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<span style="color: orange;">Are they just straight cuts? Or are you going to be shaping and sculpting?</span></div>
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<span style="color: orange;">If you're doing the 30-48" side, you can probably get away with building a big Large Scale Cutter found on the <a href="http://hotwirefoamcutterinfo.com/Diagrams.html">Diagrams Page</a>. I think one user even got away with using the Hand Block Cutter, where he mounted the wire in one corner and then just sliced off the end of the billet using the free wire. Sort of like a block cheese slicer ( <a href="https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcSGQVSGsStsRoxnWPvYFypGql3klY-x09asnaqqY_EZkCOq5oCb8g" target="_blank">Link</a> )</span></div>
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<span style="color: orange;">I almost exclusively suggest NiChrome Wire for hot wire projects, but you'll get a little better tensile strength and less wire memory with stainless steel leader wire. I've had people go through Terminal Tackle Co ( <a href="http://www.terminaltackleco.com/prod_detail_list/144">Link</a> ). The only thing is that I've never actually tested out stainless steel wire for its electrical resistance, and electrical requirements for hot wire foam cutting. From what I've read and gotten feed back on, the electrical requirements are very similar, but just know that you might have to go with a bit beefier power supply to make the wire hot enough. </span></div>
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<span style="color: orange;">Circuit Specialists ( <a href="http://www.circuitspecialists.com/">Link</a> ) recently upgraded their website and have started to stock a lot more products. For large scale cutting, you're better of going with an AC transformer - Variac ( <a href="http://www.circuitspecialists.com/variacs">Link</a> ) - because you can achieve a higher wattage for less money. I'd probably go with the 130v20a model ( <a href="http://www.circuitspecialists.com/variac-tdgc2-2.html">Link</a> ). The top end of 20 amps will allow you to get your wire pretty damn hot, and the 130 volts will give enough electrical pressure to push through the resistance of a really long wire. Whether that wire be nichrome or stainless steel. Just remember, anything over 40 volts is enough to penetrate dry human skin, so be cautious when using these models. And if you are using these in an employer-employee situation, you may have to follow some OSHA guidelines to prevent electrocution. When cutting large sections of foam, especially if your wire is hot (which will create more fumes), be sure to use in a well ventilated area.</span><br />
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<span style="color: cyan;">If you were cutting these blocks as i described above do you have a wire gage and type you would suggest ?</span></div>
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<span style="color: orange;">I would probably go for 26 gauge at the least, but not much above 22 ga, and 24 is probably going to be your best bet. The AWG scale for wire gauge is standard across all wire types, so you can always get some samples of 22, 24, 26 gauge wire at the hardware store and see what you like best. But NiCr is cheap enough to just get a few sizes. Same goes for the leader wire. </span></div>
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<span style="color: cyan;">and would you assume that i may have some nichrome wire breakage?</span></div>
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<span style="color: orange;">I think it's a possibility, but it really depends on how much pressure you're applying to the wire as it cuts. Which, really becomes a function of how fast you're cutting and the wire temperature. If it is too cold, and your applying too much force to speed up your cuts, then it will snap. But if it gets TOO hot (red/orange) then the wire will oxidize and become brittle. </span></div>
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<span style="color: cyan;">Also as you mention on your web page is 600 deg. F enough heat to cut these big blocks?</span></div>
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<span style="color: orange;">This touches on the point before… You're going to have to match speed and temperature. </span></div>
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<span style="color: orange;">Theoretically 600°F would be more than enough to cut the big blocks. But when you're cutting with such a long wire, it really becomes a matter of RE-supplying the heat to the wire, rather than achieving a cutting temperature. If that makes sense..? As you cut foam, heat transfers from the wire to the substrate and melts the foam to 'cut'. But with such a long wire, the heat will be lost from all portions of the wire and slow the cut down. </span></div>
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<span style="color: orange;">For instance, 24 gauge takes about 3 amps to reach 600°F, but you might have to bump it up to about 5 amps to make sure the entire wire stays at 600°. But if you let the wire rest for a prolonged period of time, the 5 amps will boost your wire temperature up to about 1200°F… So when you're cutting you want to make sure you have constant pressure throughout the cut, and then turn the transformer down once you've stopped. </span></div>
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<span style="color: orange;">That was sort of my thinking on the 130v20a variac. You'd have a wide range of both voltages and amperages to adjust the temperature while cutting to achieve maximum speed and efficiency. </span></div>
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<span class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px;"><span style="color: cyan;">I just have one more question... What do you mean by the leader wire?</span></span></blockquote>
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<span style="color: orange;">Stainless Steel Leader Wire - Available through Terminal Tackle Co ( <a href="http://www.terminaltackleco.com/prod_detail_list/144">Link</a> ). I don't know if you've ever large lake or deep sea fished, but basically leader wire is metal wire that precedes the fishing line. It gives you more tensile strength over long distances than you would get from normal fishing line, to prevent the line from breaking.</span><div>
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<span style="color: orange;">You might have heard of some people using "guitar strings", which is another concept of stainless steel wire. </span></div>
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<span style="color: orange;">I had a user contact me (and send me samples) of Leader Wire to test out and see how it compares to NiChrome Wire. I haven't had time to do that yet, but with Leader Wire theoretically you would get a large amount of tensile strength and prevent line breakage during cutting. Some of the RC Foam Wing creators will exclusively use stainless steel leader wire or guitar wire, because it holds up to large amounts of pressure where NiChrome may fail. </span></div>
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<span style="color: orange;">So it might be worth testing out, especially if your nichrome ends up breaking a lot. </span></div>
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LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-44683674272185798532013-04-11T14:38:00.000-05:002013-04-11T14:38:18.671-05:00Battery PowerThis message was submitted through the online contacts form. Great project and questions regarding using batteries in heating elements or even just foam cutters...<div>
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<span style="color: cyan;">I am creating a heating element with 22gage nichrome wire. Using 3.7 volt 3800 mAh Battery, trying to reach a stable temp of 500F degrees.<br />Using the Jacobs Calculator it states with 3.3amps and 3.7volts a 12.75 inch straight wire would reach the 500F temp. As i understand when coiling the wire you cut the amps needed in half to reach the desired temperature. </span></blockquote>
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<span style="color: cyan;"><br />Does this mean that the same 12.75 inch length of wire coiled will still reach the 500F temp and only draw from the battery 1.65 amps and make the battery last longer?<br /><br />or<br /><br />Does the battery still push 3.8 amps through the wire and damage the power supply?<br /><br />Do I need a longer or shorter piece of nichrome?</span></blockquote>
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<span style="color: orange;"><span style="font-family: Arial;">It looks like your estimates are correct. 3.7volts applied to a 12.75" length of 22 gauge nichrome wire will yield 3.3 amps, a theoretical temperature of 500°F</span><br style="font-family: Arial;" /><br style="font-family: Arial;" /><span style="font-family: Arial;">Here is a small section of the website dedicated to fixed voltage / batteries - </span><a href="http://hotwirefoamcutterinfo.com/__FixedVoltageCalc.html" style="font-family: Arial;">Link</a><span style="font-family: Arial;"> - There might be some information there worth reading. But I have a few things to say.</span></span><div style="font-family: Arial;">
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<span style="color: orange;">I've tested NiChrome wire in the coil arrangement on a heater project I was working on for a customer. And I've never found that "half amperage" fact to be true. It still seems like it requires the fully calculated value for amperage to achieve the desired temperature. I suppose I understand where that statement is coming from. In a coil arrangement, you are trapping and saving more heat into the empty space of the coil and less is lost to the environment. But honestly, I've only ever seen the calculated amperage to truly being effective.</span></div>
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<span style="color: orange;">The other thing is, you may not actually be able to get 3.3 amps out of that battery and expect to achieve longevity from the battery. Theoretically if you pulled 3.3 amps from a 3.8Ah (3800mAh) battery, it would run for 69 minutes. But as a rule of thumb you should never pull more current (amps) than 1/4 the rated Ah (or mAh). Since it's a 3800mAh battery or 3.8Ah, 1/4 would put you around 0.95 amps, or damn near 1 amp. </span></div>
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<span style="color: orange;">The problem is two fold...</span></div>
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<span style="color: orange;">One, not every battery can physically establish a current that high. The internal salt bridge and internal resistance of the battery actually limits the total output amperage. </span></div>
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<span style="color: orange;">Two, if you force a battery to output more than it can comfortably handle, the battery will heat up. Now, it might not explode, but with increased battery heat, comes increased battery resistance. The higher battery resistance, the lower the amperage output, and eventually the battery will die quicker. So rather than 69 minutes, you may only get 20 minutes per battery charge (just a guess). </span></div>
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<span style="color: orange;">So the 1/4 rule is really more so that you can MAXIMIZE both the output current as well as the longevity. If you go above the 1/4 rule, in most cases you will be able to achieve the desired current, but you may not achieve the desired battery life / time. </span></div>
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<span style="color: orange;">I kinda rambled a bit, but does all that make sense?</span></div>
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<span style="color: orange;"><br />In any event, when people are asking about these custom projects I always tell them that calculations are one thing.. but in-field application is another. Try to do as much on paper as you can, but eventually you're just going to have to build your heater and try it out. Some times the real life applications works better than it does on paper, which is a win-win. </span></div>
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<span style="color: orange;">So don't be too afraid of going forward with your current project as-is, but if it doesn't work out like you plan, my explanation may be the reason why. </span></div>
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Just a great question for those interested in batteries, hope it helps some of you out!</div>
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LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-78024631205163321172013-04-05T12:16:00.000-05:002013-04-05T21:24:07.749-05:00Laptop Power Supply<br />
Hello again, second posting for the day.... continuing my email purge.<br />
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Hopefully someone will find this useful</div>
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I'll be in <span style="color: #f1c232;">Orange</span>, the user will be in <span style="color: cyan;">Blue</span>. This posting starts just after the received email. </div>
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<span style="color: cyan;">Two years ago I built a foam cutter out of a laptop power supply that is still in use today at my old school.</span></div>
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<span style="color: cyan;">That leads me to my next question. I am attempting to build a more permanent and robust version and I have come across some new materials that I would be grateful if you could offer me some advice.</span></div>
<span style="color: cyan;">I have an older power supply from a computer which tells me it can put out several different supplies depending on the connectors I choose. Before I give you that info, I also want to try to use copper wire from an old IDE cable which I believe to be 30ga.and will run about 12 inches.</span></div>
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<span style="color: #f1c232;">No no no, don't use copper. Copper wire has very little resistance and will short circuit your power supply. You're going to want to stick with NiChrome Wire or Stainless Steel wire (fishing leader wire). Some people will use guitar strings, but I almost exclusively suggest NiChrome Wire. </span></div>
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<span style="color: #f1c232;">Jacobs Online ( <a href="http://www.jacobs-online.biz/">Link</a> ) has so many different options for nichrome wire and he is VERY reasonable on prices. I usually suggest 24 gauge for straight wire cutters, and 20 gauge for rigid wire (bendable) cutters.</span></div>
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<span style="color: #f1c232;">Anything smaller than 26 gauge won't really be able to withstand the force of cutting foam. Anything larger than 18 gauge is too big and unnecessary.</span></div>
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<span style="color: cyan;">The power supply says I can do 5v @ 15A, 12v @ 12A, 5vfp @ 2A, and 3.3v @ 10A. I was thinking about using the 12v @12A because that is pretty similar to what I was running off the laptop power which was 18v at about 3A with NiCr 40ga. at about 10 inches.</span></div>
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<span style="color: #f1c232;">The 5v 15a terminal can be used if you want to have a rigid wire cutter using 18 or 20 gauge. With large gauge wire you want low voltage and high amperage.</span></div>
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<span style="color: #f1c232;">For your standard table top cutter or straight wire hand held cutter go with the 12v terminal as long as your length is over 10-12". If your cutter is less than 6" go with the 5v terminal. </span></div>
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The user ended up using a different power supply, and here is his response.</div>
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<span style="color: cyan;">I used an old wall wart transformer that was 15v @ 500mA and I'm using a 9" - 38 gauge nichrome. And, so far, it's holding up quite well. I then wanted to try slightly higher production (thin foam slices) and so I strung up a total of 4 wires, and now after 5 passes, the transformer is heating up a little bit. If I wanted to to more wires, that would equal less resistance, right? So, that means I would need a higher amperage transformer, correct? Do you think I should just hook up my 350w power supply and see what happens?</span></div>
<span style="color: cyan;">I'm pretty much only doing thin foam slicing for now. However, because of the amount of donated foam I'm getting, I was thing of building a jigsaw like cutter for the art teacher in my building. Or, if I could run two cutters off of one power supply, that would even be better yet.</span></div>
<span style="color: cyan;">Let me know your thoughts. I'm not afraid to get a little crazy. Already popped the breaker a couple times when I tried to wire up a switch and pilot light. Still can't seem to get the pilot to stay lit while the cutter is on...</span></div>
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<span style="color: cyan;">I used an old wall wart transformer that was 15v @ 500mA and I'm using a 9" - 38 gauge nichrome. And, so far, it's holding up quite well. I then wanted to try slightly higher production (thin foam slices) and so I strung up a total of 4 wires, and now after 5 passes, the transformer is heating up a little bit. If I wanted to to more wires, that would equal less resistance, right? </span></blockquote>
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<span style="color: #f1c232;">Sort of… It depends on how you have your circuit arranged. Check out the Resistance Page ( <a href="http://hotwirefoamcutterinfo.com/_ResistanceCalc.html">Link</a> ), but more specifically the Circuit Theory Page ( <a href="http://hotwirefoamcutterinfo.com/__CircuitTheory.html">Link</a> ). With multiple wire foam cutters, you have to determine whether you're attaching your wires in series or parallel. The circuit theory page discusses the effects series/parallel arrangement has on resistance, voltage and amperage. </span></div>
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<span style="color: #f1c232;">Long story short, yea, if you're wires are in parallel it dramatically reduces the resistance of your overall circuit. That will in turn draw an incredible amount of amperage from your power supply UNLESS you find out a way to reduce voltage. You can always put your cutter wires in parallel, but then toss a resistor in series to reduce the current flow. </span></div>
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<span style="color: #f1c232;">If they're placed in series, it basically just mimics one long wire and one additive resistance. SO you'll have to boost voltage to achieve a cutting temperature. </span></div>
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<span style="color: cyan;">So, that means I would need a higher amperage transformer, correct? Do you think I should just hook up my 350w power supply and see what happens?</span></blockquote>
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<span style="color: #f1c232;">The 0.5amp (500mA) max output of your 15v power supply really won't be able to handle much of a load, so definitely, use your 350w power supply. Again, you may only have to use the 5v terminal if in parallel, but the 12v terminal if in series. </span></div>
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<span style="color: cyan;">I'm pretty much only doing thin foam slicing for now. However, because of the amount of donated foam I'm getting, I was thing of building a jigsaw like cutter for the art teacher in my building. Or, if I could run two cutters off of one power supply, that would even be better yet.</span></blockquote>
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<span style="color: #f1c232;">Definitely. Just think of each cutter as their own resistance circuit. So two FULL cutters placed in series or two FULL cutters placed in parallel. The same electrical properties apply as if you were using two wires in series/parallel</span>.</div>
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<span style="color: cyan;">Let me know your thoughts. I'm not afraid to get a little crazy. Already popped the breaker a couple times when I tried to wire up a switch and pilot light. Still can't seem to get the pilot to stay lit while the cutter is on…</span></blockquote>
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<span style="color: #f1c232;">Lol, thats weird… Check out my DIY power supply diagrams ( <a href="http://hotwirefoamcutterinfo.com/_DIYPSDesign.html">Link</a> ). Towards the middle of the page, you can see how you're supposed to wire a switch & pilot light with your power supply/cutter. The idea is that the switch controls the electrical flow to both your power supply and the pilot light with one throw. So you just have to split the hot wire after it <i>leaves</i> the switch. But that's all I got for you on that… I can't imagine why you're popping a fuse unless you've accidentally crossed a hot and neutral return - that would cause the electrical flow to short circuit to your breaker box every time you throw the switch. </span></div>
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LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-81230421144028327052013-04-05T12:07:00.000-05:002013-04-05T21:23:16.863-05:0060" CutterG'afternoon!<br />
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Cleaning out my saved email folder, hoping some of you can find this information useful. Read through how the conversation progressed between me and a user. Their text will be in <span style="color: cyan;">Blue</span>, I'll be in <span style="color: #e69138;">Orange</span>.<br />
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<span style="color: cyan;">Nice website. I am a foam fabricator and I am in need to build another wire cutting table/bow. I need a transformer to heat a 60" long wire. I contacted Sean at Mastech power supply, and he asked me how much current I need. I do not know. Can you help?</span></div>
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<span style="color: #f1c232;">If you'd like to talk by phone, I'll be available tomorrow any time :)</span></div>
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<span style="color: #f1c232;">What type of wire are you using for your cutter? Do you plan on using NiChrome wire, or are you going with stainless steel?</span></div>
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<span style="color: #f1c232;">I know a lot of the fabricators that have large CNC machines will use Rene Wire, or stainless steel. Nichrome wire is the preferred wire, because it has known electrical properties (resistance per foot, heat to amperage ratio, etc etc). But there is a bit of sag that occurs with nichrome wire, that is really difficult to eliminate at lengths greater than 2-3 feet. So if you're going with a 5' cutter, it might be in your best interest to go with Rene wire. I know the hobby RC plane wing creators swear by either Rene or Stainless steel leader fishing wire. </span></div>
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<span style="color: #f1c232;">If given the choice, try to stay between 20-24 gauge wire. Although, 20ga will be QUITE stiff, so go with 22-24 gauge. Anything smaller than 26 gauge will have too high of a resistance at 60" and require a high voltage output from the power supply. Anything larger than 18-20 gauge will require a much higher amperage output. Rather than getting TOO much into the details (which are also available on the website), basically you need voltage to overcome your circuit resistance, and amperage to heat the wire. The rule of thumb with ALL wire (<i>regardless of stainless, rene, nichrome</i>) :: The larger the wire, the lower the resistance, the lower the voltage, but the higher the amperage. The smaller the wire, the higher the resistance, the higher the voltage, the lower the amperage. </span></div>
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<span style="color: #f1c232;">Here are some links</span></div>
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<span style="color: #f1c232;">NiChrome Wire - Use Jacobs-online.biz</span></div>
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<span style="color: #f1c232;">Rene Wire - I recently found this link to SkyKing ( <a href="http://www.skykingrcproducts.com/accessories/foamcutterwire/renewire.html">Link</a> )</span></div>
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<span style="color: #f1c232;">Stainless Leader Wire - A user contacted me and sent me some samples from Terminal Tackle ( <a href="http://www.terminaltackleco.com/">Link</a> ) They have a great selection of stainless steel leader wire. </span></div>
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<span style="color: #f1c232;">As for current, it will depend on the wire. But if I were to buy ONE power supply that will work for almost every application, I'd go with either a 30v10a or 30v20a power supply. Depending on your budget, I'd spend the little bit more and get the 20a power supply. </span></div>
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<span style="color: #f1c232;">Here are two from Sean</span></div>
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<span style="color: #f1c232;">30v10a - <a href="http://www.mastechpowersupply.com/dc-power-supply/switching-power-supply/mastech-regulated-variable-dc-power-supply-30v-10a-hy3010e/prod_14.html">Link</a></span></blockquote>
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<span style="color: #f1c232;">30v20a - <a href="http://www.mastechpowersupply.com/dc-power-supply/switching-power-supply/volteq-power-supply-hy3020ex-30v-20a-over-voltage-over-current-protection/prod_71.html">Link</a></span></blockquote>
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<span style="color: #f1c232;">If you know what type of wire you're going to use, let me know and I should be able to estimate you a bit closer on the your required power supply. But in all honesty, I'd say the 30v20a unit will be more than enough for any hobby project. </span></div>
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<span style="color: cyan;">Thanks for the response. I am using Rene .014 " wire.</span></div>
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<span style="color: cyan;">Spool says Rene 41. My current transformer is a power stat 116ct 10 amp 50/60~ kV a 1.4 whatever all that means. It works pretty good and would like a second unit like it. I emailed Sean the same info so I will let you know what he says. I am trying to figure out an easy way to slice 30" x 48" x 96" billets into 12" thick and thinner sheets. My current table slicer table is only 30" x 72".</span></div>
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<span style="color: cyan;">Thanks for the response. I am using Rene .014 " wire.</span></div>
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<span style="color: cyan;">Spool says Rene 41.</span></div>
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<span style="color: #f1c232;">Okay, I figured as much. Rene 41 is used much more in industrial applications and actually has a lot of beneficial properties over nichrome wire. I haven't had the time to personally test the wire, but from what I've been able to find it does quite well. </span></div>
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<span style="color: #f1c232;">The only thing I haven't been able to find is a resistance per foot (ohms/foot) of Rene 41. That helps gauge power supply requirements. But if you have an electrical multimeter, you can always test the resistance of your current wire and do a little math.</span></div>
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<span style="color: cyan;">My current transformer is a power stat 116ct 10 amp 50/60~ kV a 1.4 whatever all that means.</span></blockquote>
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<span style="color: #f1c232;">Not sure what the 116ct is though, maybe a model number.</span></div>
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<span style="color: #f1c232;">the 50/60 should be 50/60Hz, which is the AC frequency of US electricity. 10 amp is the maximum safe working output amperage. If i were going to guess, it's probably a 1.4kVA power supply which is a measurement of maximum output wattage (kiloVolts * Amperage)</span></div>
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<span style="color: #f1c232;">If i were to guess, it looks like you have an AC step up transformer. Is it a Variac? A large turn dial on top, with output nodes on the front?</span></div>
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<span style="color: #f1c232;">Anyway, because this power supply is a 10a power supply, you can probably get away with another Variac or either of those two power supplies i linked in my previous email.</span> </div>
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<span style="color: cyan;">It works pretty good and would like a second unit like it. I emailed Sean the same info so I will let you know what he says.</span></blockquote>
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<span style="color: #f1c232;">Yea, sean will definitely have a better idea of what he has in stock that will work for you. But I'm sure those two DC supplies i sent you will work, but also any Variac</span></div>
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<span style="color: #f1c232;">Here is a 2kVA Variac that would work well - ( <a href="http://www.mastechpowersupply.com/variac-auto-transformer/volteq-2kva-variable-transformer-variac-2000va-0-150v-110v-input/prod_51.html">LInk</a> ), or if you wanted to go a bit bigger a 3kVA Variac - ( <a href="http://www.mastechpowersupply.com/variac-auto-transformer/volteq-3kva-variable-transformer-variac-3000va-0-150v-110v-input/prod_131.html">Link</a> )</span></div>
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<span style="color: cyan;">I am trying to figure out an easy way to slice 30" x 48" x 96" billets into 12" thick and thinner sheets. My current table slicer table is only 30" x 72".</span></blockquote>
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<span style="color: #f1c232;">If you're looking to cut them in 96" long sheets the best would be to build what I call a "horizontal cutter ( <a href="http://hotwirefoamcutterinfo.com/_HorizontalTableDesign.html">Link</a> ). Obviously what I have diagramed on the website won't work for you, but it should give you an idea of what you can set up at your own shop. I've seen some units where people just have two plumbing pipes mounted on a table with a flange and then make notch cuts in the pipe every 6" to wrap the wire around. </span></div>
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<span style="color: #f1c232;">If you're looking to cut the face of the billets off, that might be a bit trickier. Using plywood, you could build a square opening that is 32" x 50", and mount the rene wire at one top corner. Then the loose end of rene wire is free and mounted on a wooden block you would hold with one hand. You pass 12" through the wooden opening, then hand cut using the wood as your guide/fence to make sure the cut is straight and flush. You'd basically be making a large adult version of a play dough factory…. Advance the foam, cut it, advance, cut it, etc</span></div>
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<span style="color: #f1c232;">Anyway, I don't know if that helped you with the design at all?</span></div>
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<span style="color: cyan; font-size: 16px;">Thanks Carlo, I think I will get the 2K model. You have been a great help.</span></div>
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<span style="color: #f1c232;">No problem! Glad to help!</span></div>
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<span style="color: #f1c232;">Yea that 2kVa model is only a little bit bigger than the one you currently stock, and allows 13amp maximum output. So you'll be able to get the wire hotter and cut faster…</span></div>
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<span style="color: #f1c232;">Take it easy, and send me some pictures when you have your cutters made!</span></div>
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<br />LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-8769991728166800272012-12-16T22:56:00.002-06:002012-12-16T22:56:53.033-06:00Large Bendable Cutter<span style="font-family: Arial;"><i>Another question received from the website. I figured I'd post this as an FAQ. Been getting a lot of questions about power supplies lately, hopefully this will help some of you out!</i></span><br />
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<b><i><u>Question ::</u></i></b><br />
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<span style="background-color: #fac984; font-family: arial, sans, sans-serif; font-size: 13px; text-align: left;">I would like to cut large (4'-8') curved parts accurately out of 8' blocks of foam. Therefore I want pretty stiff wire, probably in the 20ga range or possibly even 18ga. Can you recommend a bench top power supply sufficient for this type of cutting and also a wire recommendation? I'm assuming that with the variability of the power supply it would also allow me to build shapeable wire routers for specific tasks, correct? </span></blockquote>
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Sounds like quite the project, a 4-8' bendable wire!</div>
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The good news is that with a large gauge wire (<i>16, 18, 20ga wire</i>) you only really have to worry about finding a power supply with enough amperage. The voltage requirement for large gauge wire is pretty low in comparison to smaller gauge wires. So almost all of your power supplies will have enough voltage, but not always enough rated amperage. </div>
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For what you're describing, 18 gauge wire will probably be the best. But the AWG scale applies across all wires. Meaning… you can go to the hardware store and pick up some copper wire, and test it to your liking. See what works best across your cutting length, bendability, rigidity, etc etc. That usually works well for most people. But honestly, <i>NiChrome Wire</i> is pretty damn cheap through <a href="http://jacobs-online.biz/">jacobs-online.biz</a>, you can always just pick up 16-20 gauge and see what you like best. </div>
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Do you have a limit on power supply cost? The <a href="http://hotwirefoamcutterinfo.com/Hot_Wire_Foam_Cutter_Info/___BenchTop.html">Bench top power supply</a> section of our website has a few great online stores to shop prices on units and shipping. I've had the best success with Circuit Specialists and MastechPowerSupply.com. Both are reputable, and focus on customer service. They may be able to answer finer details about each power supply. </div>
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<a href="http://www.mastechpowersupply.com/dc-power-supply/switching-power-supply/mastech-regulated-variable-dc-power-supply-30v-10a-hy3010e/prod_14.html">This bench top power supply</a> is pretty nice, 30v10a for $140 - great price, great range of amperage and should easily be able to handle 16-20ga. This power supply would be able to get 20g wire hotter by comparison, because 16 takes a little more amperage. </div>
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One other option is to go with something called a "Variac" power supply which is a <i>variable AC transformer</i>. I always tell people to use these with caution, because anything above 45 volts, will penetrate dry human skin. Most variacs can output 120 volts, so just be cautious about touching the metal components. BUT, with a power supply like <a href="http://www.circuitspecialists.com/variac-tdgc2-2.html">this one</a> it has an output of 20 amps for only $110! You'll have to rig a 3-prong wire on your cutter, but thats not a problem - just be sure no one gets confused and plugs it into a real live wall socket…! Generally speaking, Variacs are nice because they're cheap, and can produce a lot of power. Downside is it gets a BIT more dangerous as you use more voltage. For an application like this you're never really going to need more than 30-40 volts, so you should be safe to operate it at your cutting temperatures. But as always, just have a healthy respect for electrical currents and watch out for unintentional wire groundings. </div>
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Okay guys...! For those of you that routinely read my blog, some of this is probably starting to sound repetitive. So I hope you don't mind! Sometimes it helps to see the wide range of applications to really understand how to apply the electrical principles of hot wire foam cutting.<br />
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Take care!<br />
-carlo</div>
LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-78958012063008221662012-10-09T13:48:00.004-05:002012-10-09T13:49:13.295-05:00Wide Hot Wire Foam Cutter<br />
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Here is another question I received today from user just like you!<br />
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<span style="color: cyan;"><i>"Looking for best benchtop variabe powersupply to cut 2lb eps foam into surfboard blanks. The 26 g nicrome in bowcutter is 5ft in length. Thank you"</i></span></blockquote>
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Anyone people use cutters longer than 2 feet, I typically recommend stepping it up to 24 gauge NiCr wire. You'll get better tension and less sag using 24 over 26.<br />
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If you're truly going to work with 5 feet of cutting wire, you're going to need to have a power supply with a bit of a higher voltage output. Five feet of 24 gauge will need at least 30-40 volts if you want to get up to about 5 amps. Now… five amps is just a relative value. Most foam will cut at about 2.5 amps (when using 24 gauge). But at such a long wire, you're probably going to have to go with a hotter wire to make sure your cuts are nice and fast. A wire of that length will definitely lose some heat to the environment and take a while to replenish heat when consumed by cutting the substrate.<br />
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You probably won't be able to find a cheap DC power supply that can output 40v5a. But some of the AC step down transformers are really nice, they're called "Variacs"</div>
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Circuit Specialists have a few that they stock ( <a href="http://www.circuitspecialists.com/variacs">http://www.circuitspecialists.com/variacs</a> ). Honestly, if you don't mind spending the 100 bucks, I'd go with the 20amp model ( <a href="http://goo.gl/9o5ho">http://goo.gl/9o5ho</a> ). That thing is a BEAST. And because it can go well beyond 5 amps, you'll be able to fiddle with your cutter until you get a nice and fast cut. </div>
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But be cautious, any voltage setting above 45 volts has the ability to penetrate dry human skin. They do have an in-line fuse which will help prevent against short circuits and electrocution. But just be really careful that no one touches any of the metal components on your cutter. Also, be careful when you set the cutter down that it doesn't touch a metal bench or a puddle on the ground, or that kinda thing. I know what some people have done is spray the metal brackets/bolts with <i>GrillPaint</i>. Its a high temperature and nonconductive paint, available at most hardware stores. Just a thought. </div>
One other thing you might consider is using stainless steel leader wire, used in deep sea fishing. A lot of the model RC wing builders will use stainless steel wire because they can put it under higher tension. Now, I haven't tested it myself for the electrical requirements, but apparently it is similar to nichrome wire.<br />
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<span class="Apple-tab-span" style="white-space: pre;"> </span>Check these guys out - <a href="http://www.terminaltackleco.com/prod_detail_list/144">http://www.terminaltackleco.com/prod_detail_list/144</a></div>
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For leader wire gauge, I think the 80-100lb test is typically used, but maybe thinner. The stuff is pretty cheap, so you can experiment too. </div>
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If you guys have any questions, get a hold of me!</div>
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-carlo</div>
LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-53357093401771245912012-06-27T22:29:00.005-05:002012-06-27T22:29:51.287-05:00AC v DC<br />
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<i>Another question emailed by a user, with my reply...</i><br />
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<span class="Apple-style-span" style="color: blue;">I found your video and info on NiChrome wire interesting. I am working on a much longer run of NiChrome wire to burn through some tough fabric. Are you available to discuss AC vs DC voltages?</span></div>
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No problem at all.</div>
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Long story short, when it comes to a resistance wire application (nichrome wire) it really doesn't matter. The fact of the matter is, NiChrome wire only requires an applied electrical pressure (voltage) and a current running through the circuit. Whether its a constant flow from direct current, or an alternating flow from alternating current it doesn't make any difference.</div>
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But as far as what your specific project requires, it really depends on the length of wire and the diameter you'll require - as you may be aware, both will impact the electrical requirements. </div>
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AC power supplies are usually cheaper and have a higher voltage capability. Whereas DC power supplies are sometimes easier to come by. I always warn users to be cautious of any power supply that outputs more than 45 volts, which is the threshold for penetrating dry human skin. Not many circuits require voltages this high, so why run the risk with a high output AC transformer? But both are perfectly acceptable options.</div>
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<a href="http://www.jacobs-online.biz/transformers.htm">Jacob's Online</a> has some good solid state step down AC transformers that are beefy and can handle quite the load. So if you intend on making your own supply, check out what he has stocked. I've personally made a power supply from his units, and it works great!</div>
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Otherwise check out the <a href="http://hotwirefoamcutterinfo.com/Hot_Wire_Foam_Cutter_Info/___BenchTop.html">Benchtop Power Supply Section</a> of the website which lists a few vendors that have great customer service and a variety of power supplies. I've referenced <a href="http://www.mastechpowersupply.com/">MastechPowerSupplies.com</a> a few times, they have a great section on <a href="http://www.mastechpowersupply.com/variac/cat_3.html">AC transformers</a>. </div>
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Hope that helps!</div>
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-carlo</div>LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-77477964816789311262012-06-21T00:55:00.002-05:002012-06-21T00:55:51.513-05:00Power Supplies & Wire<br />
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<span class="Apple-style-span" style="font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif; font-size: small;"><i>Here is another emailed question from a user regarding power supplies and type of wire. </i></span></div>
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<span class="Apple-style-span" style="color: cyan; font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif; font-size: small;"><i>Hello, </i></span></div>
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<span class="Apple-style-span" style="color: cyan; font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif; font-size: small;"><i>I was looking at your webpage regarding hot wire foam cutters. I tried making a cutter but it seems that I may have bought the wrong wire. I have a toy train transformer that cuts of in about 15 seconds after it heats the wire to cut. I bought fishing wire (stainless steel)... I am very frustrated with this and really want to make this work. I'm not interested in cutting foam but as I am in cutting PVC boards. </i></span></div>
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<span class="Apple-style-span" style="font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif; font-size: small;">Hello!</span></div>
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<span class="Apple-style-span" style="font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif; font-size: small;">I would recommend spending a little time and cruise through my website, it has all the information you desire. But I think the <a href="http://hotwirefoamcutterinfo.com/Hot_Wire_Foam_Cutter_Info/Introduction.html"><span style="color: #2600f7; text-decoration: underline;">Introduction Page</span></a> may answer alot of your questions.</span></div>
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<span class="Apple-style-span" style="font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif; font-size: small;">There are a few things, stainless steel wire does not have published heating/electrical requirements so a lot of it's use is experimentation. NiChrome wire is preferred because we know how much electricity it takes to heat different lengths and gauges. That information is located <a href="http://hotwirefoamcutterinfo.com/Hot_Wire_Foam_Cutter_Info/_NiChromeData.html"><span style="color: #2600f7; text-decoration: underline;">here</span></a>. </span></div>
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<span class="Apple-style-span" style="font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif; font-size: small;">It is unlikely that the train power supply will be effective for long term use. It wasn't designed to output the wattage (amperage (x) voltage) required to heat nichrome wire (or stainless steel wire) for extended periods of time or even short periods of time. Check out the <a href="http://hotwirefoamcutterinfo.com/Hot_Wire_Foam_Cutter_Info/_PowerCalc.html"><span style="color: #2600f7; text-decoration: underline;">power supply calculations page</span></a> which will help explain why, and also provide you with ways of estimating your power supply requirements. </span></div>
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<span class="Apple-style-span" style="font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif; font-size: small;">The <a href="http://hotwirefoamcutterinfo.com/Hot_Wire_Foam_Cutter_Info/Introduction.html"><span style="color: #2600f7; text-decoration: underline;">Introduction Page</span></a> does have some general power supply information, but on the <a href="http://hotwirefoamcutterinfo.com/Hot_Wire_Foam_Cutter_Info/Materials.html"><span style="color: #2600f7; text-decoration: underline;">Materials Page</span></a> there is a link to recommended <a href="http://hotwirefoamcutterinfo.com/Hot_Wire_Foam_Cutter_Info/_Power.html"><span style="color: #2600f7; text-decoration: underline;">power supplies</span></a> for general small scale use. You may end up spending a bit to get a decent power supply, but it is worth alleviating the headache! On the <a href="http://hotwirefoamcutterinfo.com/Hot_Wire_Foam_Cutter_Info/Materials.html"><span style="color: #2600f7; text-decoration: underline;">Materials Page</span></a> you'll also find a link to purchase <a href="http://hotwirefoamcutterinfo.com/Hot_Wire_Foam_Cutter_Info/_NiChrome.html"><span style="color: #2600f7; text-decoration: underline;">NiChrome Wire</span></a>, but I have always had superior customer service and recommend <a href="http://jacobs-online.biz/nichrome_wire.htm"><span style="color: #2600f7; text-decoration: underline;">Jacobs-Online</span></a> for nichrome wire. </span></div>
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<span class="Apple-style-span" style="font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif;">I know there wasn't a lot of content in this FAQ, but I just wanted to post so you can see the types of questions we receive. Also, I wanted to post the links to the website in case you too have similar questions. I always recommend people start out by reading through the introduction page for abridged notes to foam cutters. </span></div>
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<span class="Apple-style-span" style="font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif;">-Carlo</span></div>LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-65480171056809337172012-02-18T22:09:00.003-06:002012-02-18T22:10:07.846-06:00Adding Resistance<br />
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<i>Here is another email from a user that has a perfect question regarding power supply voltage... check it out!! This is the exact question (in blue) and my reply (in black)</i></div>
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<span class="Apple-style-span" style="border-collapse: collapse; font-family: arial, sans, sans-serif; font-size: 13px;"><span class="Apple-style-span" style="color: #0045dc;">Question ::</span></span></div>
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<span class="Apple-style-span" style="border-collapse: collapse; font-family: arial, sans, sans-serif; font-size: 13px;"><span class="Apple-style-span" style="color: #0045dc;">I want to make a hot wire cutter to cut rabbets in the edges of rigid styrofoam insulation. I have calculated my voltage and current requirements with the calculator on this site.</span></span></div>
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<span class="Apple-style-span" style="border-collapse: collapse; font-family: arial, sans, sans-serif; font-size: 13px;"><span class="Apple-style-span" style="color: #0045dc;">To heat my 1" 18ga Nichrome wire to 300F/600C, I need ~6.5A at 0.25V.</span></span></div>
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<span class="Apple-style-span" style="border-collapse: collapse; font-family: arial, sans, sans-serif; font-size: 13px;"><span class="Apple-style-span" style="color: #0045dc;"><br /></span></span></div>
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<span class="Apple-style-span" style="border-collapse: collapse; font-family: arial, sans, sans-serif; font-size: 13px;"><span class="Apple-style-span" style="color: #0045dc;">My variable power supply won't go that low, and because this is a one-time project, I don't want to spend $30-40 on batteries and another $30-40 on an appropriate charger.</span></span></div>
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<span class="Apple-style-span" style="border-collapse: collapse; font-family: arial, sans, sans-serif; font-size: 13px;"><span class="Apple-style-span" style="color: #0045dc;"><br /></span></span></div>
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<span class="Apple-style-span" style="border-collapse: collapse; font-family: arial, sans, sans-serif; font-size: 13px;"><span class="Apple-style-span" style="color: #0045dc;">I'm looking for suggestions for a voltage divider that would allow me to use an existing [<i>variable voltage</i>] 12VDC 10A power supply to power the cutter.</span></span></div>
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No problem at all, and great research! I always love when people like you utilize the website and have almost all your own answers!</div>
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You're close :) All you have to do is increase the resistance of your circuit to account for the lowest power supply voltage. </div>
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Just play with ohms law to see how much you need to add, but here is the link to the main page for resistance modification</div>
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<a href="http://hotwirefoamcutterinfo.com/Hot_Wire_Foam_Cutter_Info/_ResistanceCalc.html">http://hotwirefoamcutterinfo.com/Hot_Wire_Foam_Cutter_Info/_ResistanceCalc.html</a></div>
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You'll be adding resistance in <b><u>series</u></b> with your nichrome wire circuit. </div>
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Here is a quick series of calculations you can do, figuring the lowest voltage your power supply can output. Lets just use 2 volts (just guessing) as the lowest voltage your supply can provide. </div>
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Resistance = Voltage / Current</div>
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Resistance = 2/6.5</div>
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Necessary Circuit Resistance = <span class="Apple-style-span" style="color: #c60000;">0.307 ohms</span></div>
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Resistance of 1 inch 18 gauge wire = <span class="Apple-style-span" style="color: #0034af;">0.035ohms</span></div>
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Unaccounted Resistance = <span class="Apple-style-span" style="color: #c60000;">0.307</span> - <span class="Apple-style-span" style="color: #0034af;">0.035ohms</span></div>
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Unaccounted Resistance = 0.272 ohms</div>
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So basically, all you have to do is add about 0.3 ohms and you can use a power supply that can only go as low as 2 volts (theoretical).</div>
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<span class="Apple-style-span" style="font-family: Helvetica;">A REALLY cheap way to make a resistor is like this</span><br />
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<a href="http://www.youtube.com/watch?v=P92V6jBYCA0">http://www.youtube.com/watch?v=P92V6jBYCA0</a></div>
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<span class="Apple-style-span" style="font-family: Helvetica;">I've never tried to pull more than a few amps through that wire, but theoretically it could handle quite a lot. I get a little wordy in the video, so I apologize, i haven't updated that video yet. But you should get the idea. I had also considered using a frayed telephone cable (which has 4x small cables in it) but you might melt that small of a cable. Anyway, a little playing around might save you some money.</span><br />
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Otherwise check out Digi-Key, this link goes straight to their resistor search page</div>
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<a href="http://search.digikey.com/us/en/cat/resistors/through-hole-resistors/66690">http://search.digikey.com/us/en/cat/resistors/through-hole-resistors/66690</a></div>
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On hand, I have 1ohm5Watt resistors. So placing a handful in series or combined series / parallel will provide a lot of circuits with the resistance and wattage they'd require.</div>
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I hope that wasn't too confusing!!</div>
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-carlo</div>LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-27804659649954632232011-12-03T00:36:00.001-06:002011-12-03T01:02:35.093-06:002011, 1202 - YouTube UpdateHello Everyone,<br />
Thank you for visiting our blog and here are some brief links for the most recent YouTube Update (2011, 1202)<br />
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Main Link to JacobsOnline - http://jacobs-online.biz/<br />
Step Down Transformers - http://jacobs-online.biz/transformers.htm<br />
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I have selected the XFR-1006D as my primary power supply. As a sneak preview, here is the diagram I showed in the video but will be creating a custom power supply within the next month or so.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiAsGMV-IZTJ85giFeYxDn01UZ_ZnYRQFnGbApCmtgBpX8LlykKVje7umFARNGo2cemDw5l9MjMZmDFliYzou4oeQoHuH88iNC1YxXT40cCmc3m5LZxraswaxceRNG-SnpyAs4v3nMUYk44/s1600/Full-Wiring-Diagram.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="251" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiAsGMV-IZTJ85giFeYxDn01UZ_ZnYRQFnGbApCmtgBpX8LlykKVje7umFARNGo2cemDw5l9MjMZmDFliYzou4oeQoHuH88iNC1YxXT40cCmc3m5LZxraswaxceRNG-SnpyAs4v3nMUYk44/s320/Full-Wiring-Diagram.png" width="320" /></a></div>
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This electrical arrangement will allow for three power states from this supply - 6v8.3a, 6v16.7a, 12v8.3a - when the DPDT switch toggles the circuit to series (double voltage), parallel (double amperage), & off (single voltage, single amperage.<br />
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All that for a transformer under 30 bucks!! (yes yes... there are other costs in the switches, etc, but c'mon 30bucks!)<br />
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Stay tuned for more videos!LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0tag:blogger.com,1999:blog-896237542409363490.post-27338324314429024322011-11-07T20:18:00.001-06:002011-11-07T20:18:32.062-06:00Large Scale Cutting<br />
Hello everyone,<br />
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Just another question on cutting foam..! I've gotten this one a few times before, not necessarily for surf boards, but just larger hand held projects. The questions are in blue, take a look!<br />
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<span class="Apple-style-span" style="color: blue;">I am a surfboard builder and am interested in cutting blanks out of EPS foam -I know nothing about electrical systems but would like to build my own cutting tool- </span></div>
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<span class="Apple-style-span" style="color: blue;">what do you recomend for this type of project?</span></div>
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I'd certainly recommend a large scale hand held cutter</div>
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http://hotwirefoamcutterinfo.com/Hot_Wire_Foam_Cutter_Info/_LargeHandDesign.html</div>
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<span class="Apple-style-span" style="color: blue;">the bow needs to be aproximately 32" inches wide. </span></div>
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You should easily be able to make this cutter at any length you desire. </div>
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You could even use 3/4" PVC rather than 1/2". The 3/4" will be a bit heavier, but will be more rigid and strong for larger cuts. </div>
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If you want me to make you the electrical end caps, just let me know and I can send them to you. But I will be uploading some new videos tonight, so you may be able to follow along in those and make them yourself. </div>
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<span class="Apple-style-span" style="color: blue;">what should I use as my power source? ( I have been looking at variacs on ebay)</span></div>
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The variac series are nice. They are an AC power supply rather than the typical DC power, which works well at a wide range of voltages and amperes.</div>
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mastechpowersupply.com has the greatest selection of variacs available online, and they are very reasonably priced. Check out what they have for AC transformers, and you can always get model numbers to see what you can find online. </div>
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http://www.mastechpowersupply.com/variac/cat_3.html</div>
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Be VERY VERY careful when using AC transformers. Typically any voltage above 45 volts can penetrate human skin and cause electrocution. While you'll probably need less than 20 volts, ever, this wont be a problem. But just be careful!</div>
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Here are two power supplies I'd choose for your project</div>
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http://www.mastechpowersupply.com/variac-auto-transformer/0-5k-va-variable-transformer-variac-500va-0-150v-110v-input/prod_52.html</div>
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http://www.mastechpowersupply.com/variac-auto-transformer/mastech-2kva-variable-transformer-variac-2000va-0-150v-110v-input/prod_51.html</div>
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The first one SHOULD be enough power for you. It says it can only put out 3.3 amps at 150 volts, but its rated as a 500VA (or watt) transformer. So at lower voltages you should be able to safely obtain a higher amperage. I'd guess the first one will be more than enough for your project, but the second one will DEFINATELY work!</div>
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<span class="Apple-style-span" style="color: blue;">I can build the cutting bow but dont know what gauge on nichrome wire to use or if it would be best to use stainless steel.</span></div>
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I would recommend NiChrome, only because it is most reliable and there are known electrical values. (Meaning, we know how much amperes/voltage it requires to heat up.)</div>
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I'd recommend either 24 gauge or 22 gauge wire. 20-22 gauge are pretty stiff, so might not be ideal. I've personally used 26 gauge at lengths under two feet, but you should probably use 24 gauge.</div>
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the good news is, Nichrome is CHEAP. so you can always buy 24 and 22 and see which you like better.</div>
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On the other hand, with the variac transformer you will be able to test out 22 gauge, 24 gauge nichrome, as well as stainless steel if you wanted. The power supplies are hearty enough that they will heat up a lot of different wires. </div>
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Check out this fishing line retailer, they have stainless steel fishing line, that I had a customer use for making RC plane wings. He said he liked it better than nichrome at longer lengths and is pretty cheap too. </div>
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http://www.terminaltackleco.com/</div>
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<span class="Apple-style-span" style="font-family: Helvetica;">here is the link to their stainless steel leader wire page</span><span class="Apple-style-span" style="font-family: Helvetica;"><br /></span><blockquote class="webkit-indent-blockquote" style="border-bottom-style: none; border-color: initial; border-left-style: none; border-right-style: none; border-top-style: none; border-width: initial; font-family: Helvetica; margin-bottom: 0px; margin-left: 40px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;">
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http://www.terminaltackleco.com/prod_detail_list/144</div>
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<span class="Apple-style-span" style="font-family: Helvetica;">I don't remember the recommend lb test wire, but I THINK it was between 30-60lb test stainless steel wire that worked the best. But at a few dollars per pack, it's still pretty cheap to buy a variety of wires, and see what you like!</span><br />
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<span class="Apple-style-span" style="font-family: Helvetica;">________</span><br />
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<span class="Apple-style-span" style="font-family: Helvetica;">That's it guys! I hope it was some what informative. And remember, all those links are already on the website!</span><br />
<span class="Apple-style-span" style="font-family: Helvetica;"><br /></span><br />
<span class="Apple-style-span" style="font-family: Helvetica;">-carlo</span><br />
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<span class="Apple-style-span" style="font-family: Helvetica;"><br /></span>LetsCutFoamhttp://www.blogger.com/profile/16484982934640335929noreply@blogger.com0