Hot wire cutting.

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Geraldc

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For cutting foam without a fancy machine or using templates I see some people are using 1/16 stainless tig wire and bending it to the profile they need.
 

Pops

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Make the shape you want out of #12 copper house wiring. Put it in your pistol type of soldering gun.
 

Geraldc

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1/16 wire works fine but you have to keep the heat just below where the wire looses its strength.
 

stanislavz

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For cutting foam without a fancy machine or using templates I see some people are using 1/16 stainless tig wire and bending it to the profile they need.
Too much heat, it leaves you with not nice surface. You want to go as thin as possible wire (0.2-0.25mm) and be as steady with speed as possible.
 

Pops

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On hot wiring large model airplane wings you really need two people. Same with our larger airplanes. Have the edge of the templates very smooth and marked off in numbers and have one person calling off the numbers so each can stay in sync with the other . Yep, tight, thin wire, temp set correctly and the more you do the better the results.

Never seen an old model airplane builder that didn't built a beautiful homebuilt.
 

Pops

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I have used both many times. Like you said nichrome wire is hard to find. Back when modelers built airplanes most hobby shops stocked nichrome wire. Now balsa wood is hard to find. Your thin .032" SS safety wire works good. The hardest part is getting the wire temp correct for the length of the cut for a smooth surface. Nice to have the same length practice pieces of foam to adjust the temp on first.
 

Jay Kempf

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.032 SS safety wire here for 50" wire frame and a simple dimmer switch control. I have a 4 axis CNC cutter but since I got the router I haven't touched it as it is so limited in scope.
 

Dusan

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For compound shapes as in channel wing or lip wings, actually any curved wings, I made a jig where I use stainless steel 16 gauge, shaped as the airfoil, and program the cnc to do the curved shape of the wing. The current needs to be increased between 8-10A
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Norman

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On hot wiring large model airplane wings you really need two people. Same with our larger airplanes. Have the edge of the templates very smooth and marked off in numbers and have one person calling off the numbers so each can stay in sync with the other . Yep, tight, thin wire, temp set correctly and the more you do the better the results.

Never seen an old model airplane builder that didn't built a beautiful homebuilt.
We tried the method of 2 people guiding the ends of the wire. Hated the results so we built a drop bar cutter out of a piece of 1x2 lumber and some shower door rollers. The gravity driven drop bar provides constant pressure on the wire which eliminates the source of errors, which are ripples from overheating the foam during pauses to let one guy catch up. It's also much cheaper than CNC. Here's a video of a commercial drop bar cutter. That little wheel that supports the bow is nothing but a problem. We just hold the bow vertically over the blank and follow the wire as it melts through.
 

billyvray

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Dusan, how about showing your setup? I'm considering a cnc foam cutter (and a lowrider cutter). I like your solution to the curved shapes. It actually seems so simple (why didn't I think of that....duh)...


 

Dusan

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Dusan, how about showing your setup? I'm considering a cnc foam cutter (and a lowrider cutter). I like your solution to the curved shapes. It actually seems so simple (why didn't I think of that....duh)...
Actually the whole cnc machine build is presented here:
 

Geraldc

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Actually the whole cnc machine build is presented here:
This opens up more options.
I see you were deciding between steppers and servos.
I went with steppers for my machine but am thinking of replacing them with these which are a direct replacement.
 

cblink.007

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.032 SS safety wire here for 50" wire frame and a simple dimmer switch control. I have a 4 axis CNC cutter but since I got the router I haven't touched it as it is so limited in scope.
That is what I use, and it works well. Found the box at Hobby Lobby, and sourced the internals at Lowes:

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As enjoyable as it was, I am not looking forward to doing this again for the full size plug (the finishing part at least)! Will not use plywood templates, though...we will have the full scale ones cut from stainless steel.
 

Pops

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I always had trouble using plywood templates. Couldn't get the edge smooth enough where the thin hot wire wouldn't dig in a little and get caught and make a rough place on the surface of the foam. Went with thin aluminum and polished the edges.
 
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