Large Bendable Cutter

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!

Question ::

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? 

Response ::

Sounds like quite the project, a 4-8' bendable wire!

The good news is that with a large gauge wire (16, 18, 20ga wire) 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. 

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, NiChrome Wire is pretty damn cheap through jacobs-online.biz, you can always just pick up 16-20 gauge and see what you like best. 

Do you have a limit on power supply cost? The Bench top power supply 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. 

This bench top power supply 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. 

One other option is to go with something called a "Variac" power supply which is a variable AC transformer. 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 this one 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. 

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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.

Take care!
-carlo