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 Blue, I'll be in Orange.
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?
If you'd like to talk by phone, I'll be available tomorrow any time :)
What type of wire are you using for your cutter? Do you plan on using NiChrome wire, or are you going with stainless steel?
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.
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 (regardless of stainless, rene, nichrome) :: 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.
Here are some links
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.
Here are two from Sean
30v10a - Link
30v20a - Link
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.
Thanks for the response. I am using Rene .014 " wire.
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".
Thanks for the response. I am using Rene .014 " wire.Spool says Rene 41.
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.
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.
My current transformer is a power stat 116ct 10 amp 50/60~ kV a 1.4 whatever all that means.
Not sure what the 116ct is though, maybe a model number.
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)
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?
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.
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.
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
Here is a 2kVA Variac that would work well - ( LInk ), or if you wanted to go a bit bigger a 3kVA Variac - ( Link )
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".
If you're looking to cut them in 96" long sheets the best would be to build what I call a "horizontal cutter ( Link ). 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.
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
Anyway, I don't know if that helped you with the design at all?
Thanks Carlo, I think I will get the 2K model. You have been a great help.
No problem! Glad to help!
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…
Take it easy, and send me some pictures when you have your cutters made!