h a l f b a k e r yThis ain't rocket surgery.
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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.
Protospace's Rabbit laser cutter
http://wiki.protospace.ca/6
Mentioned in my anno [notexactly, Feb 11 2019]
Hot wire cutter shapes
http://www.carlpisa...ireCutter_MAIN.html
[bs0u0155, Feb 12 2019]
[link]
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What exactly do you teach the wire? |
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Is this machine meant for Ohm use only ? |
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Clearly, its resistance has utility. |
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We have a battery of questions about how the device would be powered, but does [xen] have the capacity to answer them? |
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Well this is just revolting. |
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// this is just revolting. // |
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Yes, but there may be the spark of an idea in it. |
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The machine could cut both foam and cheese; that would make it a Joule-purpose tool ... |
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That's quite a stretch. Discharges may apply. |
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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. |
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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. |
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of course, the hot wire itself would not have to extend to the
ceiling, just to an appropriately-anchored conductor. |
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The orientation could also be horizontal so that
the device can operate like a thicknesser. |
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Those are both good ideas. |
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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. |
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How come nobody did "band saws, you don't need to
hotwire them" ting. |
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Wouldn't a laser be more fun? I'm guessing a 10W laser would
be more than sufficiently adequate. |
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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. |
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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. |
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{snaps fingers in front of [MaxwellBuchanan]'s glazed eyes} |
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Actual band saw? It's only foam, you could get away with a
coping-saw thin blade. |
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If that was totally true then the hot wire foam
cutters wouldn't exist. |
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//If that was totally true then the hot wire foam cutters
wouldn't exist// |
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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. |
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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. |
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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. |
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