Help please: cutting styrofoam sheets

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On Wed, 20 Nov 2013 07:23:58 -0800 (PST), snipped-for-privacy@aol.com wrote:

I haven't tried this on styrofoam. I bought new a heater element, metal covered covered tube, 1/4 or so inches in diameter,, 10 inches long, runs on 110AC. I've used it to bend lucite or lexan, narrower than the heater is long. Mine is not that hot, although I've never touched it.
But if you got a toaster oven out of the trash, each element runs on 110-120VAC and many/most brands are not just the coiled wire, but they are some sort of glass or metal. tube. It might cut styrofoam well, or not, or maybe it will be too slow. Worth a little upfront, then you'd always be able to do so.
They sell the elements new too, I'm sure.
I think they get hotter than the one I have, or maybe it just seems that way because there are 4 of them on the top and 4 on the bottom (or 2 and 2)
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A regular toaster (for bread and such) has bare, metal bands that are straight for, I guess, 6 inches. Other than figuring out how to make it work without burning something up, this would appear to be an ideal place to start. Though, some older toaster ovens have the same set up and might provide longer lengths of the bands. Its just a matter of holding one in place without a shock/fire hazard, and after measuring the resistance of the entire device, replicate that resistance via high wattage dimmer switch and maybe a few power resistors or maybe even some form of DC feed instead of AC with a resistance adjusted for the DC voltage. More of an electronics question at that point.
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Make one.
I did, when I worked at a govt resarch lab. Hadda make several shipping containers lined with various sizes of polyethyline foam insulation. I made a 3-1/2 ft deep hot wire cutter scroll saw type cutter using chromium wire and a variac. Strung the wire across two pieces of shelving rails bolted together to make the scroll saw frame, hooked wire to a AC variac, and turned it up till the wire got hot enough. Worked perfectly and we cut all sheets of foam in 1 day, which woulda taken several days by any other method. Granted, we had access to the worlds greatest govt hardware store, yet this crude idea worked perfectly. Basically only need an AC variac and some chromium wire and a few insulators. You can knock out the scroll saw frame from most anything.
nb
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dont forget insulation like this is VEY FLAMMABLE, and should be completely covered by dry wall or a minor spark could start a major fire....
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bob haller;3152461 Wrote: > dont forget insulation like this is VEY FLAMMABLE, and should be > completely covered by dry wall or a minor spark could start a major > fire....
A minor spark could start a fire?
Bob, I'll concede that polystyrene is flammable, but if you've ever tried to burn the stuff you'll realized it's kinda hard to get it burning. It melts and pulls away from the source of heat.
If it was as flammable as you're suggesting, it wouldn't be used as insulation in virtually all of the flat roofs on the continent.
--
nestork


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The 3.5 year old OP did say it was a shop. Things in shops sometimes make sparks.
I'm not saying drywall on a garage door isn't worth shaking your head over, but the warning itself has (some) merit. The suggested solution, well, not so much. ;-)
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On 11/20/2013 4:01 PM, DerbyDad03 wrote:

But at some point, the weight is gonna be a problem.
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A sharp utility knife will cut about 1" deep, then turn it ove and cut the second inch from the other side. This is not rocket science, hardly even worth posting here!!!!!!!
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Yeah, I have done that but didn't want to post it and seem to be nefarious.
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A little air gap is needed for reflection. The inside foil also helps with reradiating inside.
Greg
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