Modelling foam can be cut with a hot wire instrument but I am proposing a variation on this simple device. It's a bit practical (apologies)
For those who have not used one, a taught wire is heated via its electrical resistance and the wire will then cut through any suitable foam pressed hard against it.
In the new improved version, the wire is no longer static, but continuously moves as it rotates around two large diameter wheels in the same way as that of a band saw.
This gains the advantage of producing a constant supply of clean hot wire, free from melted debris, which is removed as the wire passes through sets of bristles inside the machine. This moving wire results in more precise cuts being made.
Because it's moving, the hot wire can now also be abbraisive, which helps even more with the cutting action, and used to cut other materials that don't need the melting function.-- xenzag, Feb 06 2019 Protospace's Rabbit laser cutter http://wiki.protospace.ca/6Mentioned in my anno [notexactly, Feb 11 2019] Hot wire cutter shapes http://www.carlpisa...ireCutter_MAIN.html [bs0u0155, Feb 12 2019] What exactly do you teach the wire?-- MaxwellBuchanan, Feb 06 2019 Current events.-- whatrock, Feb 06 2019 Watt?-- MaxwellBuchanan, Feb 06 2019 Ample information.-- whatrock, Feb 06 2019 Is this machine meant for Ohm use only ?-- 8th of 7, Feb 06 2019 Clearly, its resistance has utility.-- MaxwellBuchanan, Feb 06 2019 We have a battery of questions about how the device would be powered, but does [xen] have the capacity to answer them?-- 8th of 7, Feb 06 2019 Well this is just revolting.-- 2 fries shy of a happy meal, Feb 06 2019 Grohms....-- xenzag, Feb 06 2019 // this is just revolting. //
Yes, but there may be the spark of an idea in it.
The machine could cut both foam and cheese; that would make it a Joule-purpose tool ...-- 8th of 7, Feb 06 2019 That's quite a stretch. Discharges may apply.-- 2 fries shy of a happy meal, Feb 06 2019 I find that melted foam stuck to the wire gets vaporized within a few seconds, so you might not need the bristles, as long as you can avoid the wire being cooled by the wheels. Maybe make them out of a high-temperature plastic, or, for impracticality, aerogel.-- notexactly, Feb 07 2019 I was envisioning a wire that extended from the table to a point on the ceiling. This would allow you to make large cutouts without an arm in the way. Most machines have a limited throat because of the mechanics involved. This isn't really necessary with a hot wire.
of course, the hot wire itself would not have to extend to the ceiling, just to an appropriately-anchored conductor.-- nomocrow, Feb 07 2019 The orientation could also be horizontal so that the device can operate like a thicknesser.-- xenzag, Feb 07 2019 Those are both good ideas.
You could have actually infinite throat (well, not actually—still limited by the surroundings) by having a non-looped wire, and a spool on each side of the cutting area. One pays out and one takes in. Then, when the end of the wire is reached, they reverse. They can coordinate by radio link and use independent power supplies if a cable would get in the way of the workpiece. There still needs to be a return path for the current through the wire, but that can go through the ground if necessary. Or you can just put the cable along the ground, because the ground is going to be there, limiting your throat, no matter what.-- notexactly, Feb 07 2019 How come nobody did "band saws, you don't need to hotwire them" ting.-- not_morrison_rm, Feb 09 2019 [+]-- 21 Quest, Feb 10 2019 Wouldn't a laser be more fun? I'm guessing a 10W laser would be more than sufficiently adequate.-- MaxwellBuchanan, Feb 10 2019 The laser would present some of the current problems of the static wire - accumulation of melted foam or its conversion into black blobs; difficulty in pacing speed of feeding foam through the blade. I believe with a moving wire, there would be much greater control possible. A laser would also be silent. There is a certain amount of haptic satisfaction in the sound of a moving blade slicing through any material.-- xenzag, Feb 11 2019 Yes, but...lasers!-- MaxwellBuchanan, Feb 11 2019 Lasers can also cause foam to catch fire. That's how we got the [linked] laser cutter: the owner was cutting some foam, went to the bathroom, and came back to tall flames coming from it. (That's why it has scorch marks on the front of the lid.) He bought a new one because he was using it for business, and gave us the old one to fix in exchange for some web design that I don't think ever got done. Anyway, we have a rule that you have to keep a close eye on it, especially when cutting foam. As long as you do keep a close eye on it, laser cutting of some foams works pretty well. But we also have some hot-wire foam cutters, because there are some tasks a laser cutter isn't good for. A hot-wire bandsaw would be a good addition, I think.-- notexactly, Feb 11 2019 Yes, but... lasers!-- MaxwellBuchanan, Feb 11 2019 {snaps fingers in front of [MaxwellBuchanan]'s glazed eyes}-- pertinax, Feb 11 2019 Water jet?-- RayfordSteele, Feb 12 2019 Actual band saw? It's only foam, you could get away with a coping-saw thin blade.-- bs0u0155, Feb 12 2019 If that was totally true then the hot wire foam cutters wouldn't exist.-- xenzag, Feb 12 2019 //If that was totally true then the hot wire foam cutters wouldn't exist//
I think the reason they exist is simplicity. An old guitar string a car battery and a simple wooden frame, you're off to the races.
I'm actually pretty impressed with some of the shapes and profiles that can be cut with simple equipment <link>. I thought the heat might be a neat way of improving the surface finish, but reading around suggests that it isn't. The surface is pretty nasty.
Maybe a moving "blade" made of say carbon fiber tow optimized to pick up acetone solvent. That way it could melt its way through leaving a nice sealed surface. Then follow the solvent cutter with a hot wire to rapidly flash off the acetone to limit off-target melting. You'd pick a temperature above the boiling point of acetone, but below the foam, that's a nice wide window.-- bs0u0155, Feb 12 2019 random, halfbakery