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what would I use to make a hotwire cutter with stiff wire in a curved shape for cutting curves? Answered

what kind of tansformer would I need ? what kind of stiff wire? thanks!?



5 years ago

I know this is old, but for others...

Stainless steel is your best friend here, resistance is fairly high and it is also pretty strong and stiff at foam cutting temperatures. Easy enough to scrounge from a welder. TIG rods can usually be found at 1/16" and up, MIG wire down to 1/32". Nichrome isn't quite as strong, is much harder to find and costs more. That said it does work pretty well if you find some. Plain steel wire will also work, but needs a lot of current, it won't take the heat without wilting that stainless or nichrome will. The current and voltage you need depends on the size and length of wire you use. A metre of 1/16" (1.6mm) welding rod might want about 6V and 15 amps. Thinner wire will want a few more volts but less current. Having something you can adjust is the key. Home made resistors using bits of wire can be used in lieu of an adjustable supply. Car/motorcycle batteries are good for high current. Find some wire and make a mess till you get it right!


7 years ago

Thir are different gauges of ni-chrom wire used by manufacturers on their CNCs. Thicker can do it. We used to use certain welding rods as cutting wires, pass current thourgh transformer and dimmer and through wire thaty is shaped and mounted to outside of turntable on which foam is mounted.


8 years ago

I did EPS foam columns/molding for years. The best/cheapest wire I found is filler rod (used for welding) with a variable transformer for fine control of heat. I've heard you can use a dimmer running a step down transformer as a power supply - seems doable. Filler rod is a bit hard to bend so use the smallest diameter you can manage but the wire sags if it gets too hot - experiment. Pre-heat the wire until red hot and back off the heat just a bit below glowing. Bear in mind that the finer the wire the more the wire drags in the foam, distorting the cut. You'll have to experiment a bit and develop a feel for the drag on the wire: too slow and it melts too much kerf, too fast and the wire bends. You want the foam to be just liquid and develop the feel of the wire 'sliding' through the liquid foam. Watch the smoke color carefully - when it's too brown it's about to catch fire. The simplest cutter for curves is to use a piece of of cement backer board with a slot shaped hole cut in it for the terminal bolts. You can just drill a couple of holes for the bolts but then you'll want make something else that requires another hole distance.... so just go ahead and cut the slot and save the work later. You can attach the backer board to a 1x1 or 2x2 and use it like a compass for large curves or just hold the backer board and try to free hand the small stuff - that's tough to do. You'll find it best to make jigs and holders for everything. Use your imagination. Foam is so easy to work with it's fun but as a material it has a learning curve like no other material you've used. Your imagination is the only limit.

Old Doc

8 years ago

The thickest wire you could use for curves is the core wire from old Coax cable, and even that's so thick that I couldn't even tell ya what voltage + amperage to use.


10 years ago


I'm not sure of your question but a foam cutter "hotwire" is usually thin so you don't need to run tremendous power through it to get it hot. If you wanted to create a "curved" shaped blade for cutting out shapes, and being stiff enough would make it a bigger wire to heat up. I think you would burn the piece and set it ablaze before the wire got through the foam. You normally have to cut straight segments and "sculpt or pare" the shape down to a curve. Good luck.