Re: OT? Styrofoam cut by hot wire

Does anyone here have a good idea for cutting foam blocks with embedded plastic? (Insulating Concrete Forms)

These are blocks used for construction. Two pieces of foam are connected with plastic rebar and concrete gets poored in the middle.

Currently, most people using these cut the blocks with a chain saw/table saw, resulting in poor cuts and major wear on the tools.

Any thoughts appreciated...the plastic makes this a little tricky. Note the concrete only gets poored in later, so there is no need to cut through concrete :-)

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> > Whoa, dude! I was interested in the thread about cutting styrofoam with a > hot wire. Well, some months ago I saw a hank of nichrome wire on ebay, for > a couple of bucks, which he said was #36, and just today I mic'd it [yes, > that's proper use of the apostrophe - go look it up! - Rich the Pedagogue] > at about .0047, maybe .0048. The thou on Joe's mic are like an eighth of > an inch apart, so I had to interpolate the tenths. > > Anyway, in the ad that I bought it from, it said, "28 ohms per foot." I > ohmed it out, and it was within as close as I could get the probes to a > foot apart. :-) > > BTW, the reason I bought it is because I was entertaining fantasies of > building a THC evaporator. [still am, actually - Rich the proofreader] > > But that's a different story. %-) What prompted this post is that I have a > "7.5VDC, 1A" wall wart that came with some kind of radio that somebody > threw away, a set of Radio Shack clip leads, and this nichrome wire. > "Hmm", I says to meself. Did I say I'm still stoned from that ONE HIT!??) > > But I remembered that "cut foam with a hot wire?" thread, and I thought, > what's the worst that could happen? So I took a piece almost a foot long, > clipped the clip leads to the ends - you can barely see the red-booted > clip and red VOM lead, which for the pic have been disconnected. I just > clipped the wall wart to a piece of this nichrome wire, on top of a couple > of pieces of ceramic tile I'd scrounged, and it didn't get red, but it got > uncomfortably warm to the touch, like, if I'd held it tightly between > thumb and finger, it'd have left a mark in a few seconds. I don't know how > to estimate temp, but I'd say more than 120 F, but decidedly less than > 450! :-) So, anyways, this nichrome wire is lying there dissipating heat, > and I grabbed this styrofoam block, and picked up the wire by the clips, > and, well, I cut the styrofoam. :-) It was kind of a weird feeling, > actually - I felt almost no resistance (in the mechanical sense) as if I > were cutting butter, please excuse the trite hackneyed cliche. ;-) > > Just for context, in the pic you can still see the nichrome wire, and it > looks like it goes into the right-hnad corner of the small block and out > of the top corner? Well, here's the thing. I was so freaking excited at my > wonderful new discovery that I left the wire lying about where you see it > in the picture, and by the time I got around to unclipping the leads from > the wall wart plug, the wire had already melted itself into the botttom of > the small block. > > The cavity that looks like a hole somebody tried to drill, who didn't know > what an ordinary drill bit will do to that type/form of styrofoam, is a > hole somebody (I) tried to drill, not knowing what an ordinary drill bit > will do to that type/form of styrofoam. ;-) > > But the way the wire cut through it! I did feel the difference, but that > cut is amazing! I did that by hand! Imagine if I put it in some kind of > fixture! > > BWAHAHAHAHAAAA! Styrofoam cut to your spec - $0.12 per square inch of new > surface!! ;-D ;-D ;-D > >
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> > BTW, if you get another server error, please, please let me know, because > as I've said, I'm inside the firewall, and I have to trust my own > blundering configurations to expose just the right stuff to the outside > world. Damn, I'm still stoned, on that one hit, and it's been a couple > hours! I might have another little hit soon though, since it _has_ been a > couple hours. %-} > > Oh, yeah, before I hit "send" if you're wondering where that particular > particularly nice block of styrofoam came from, it was in a box that > somebody had shipped some big light bulbs that they've installed in the > shop. Like the size of a 1,000 watt bulb, but halogen or mercury or > something - anyway these big bulbs were packaged in these cool blocks of > foam. :-) (inside corrugated cardboard boxes, of course.) > > Cheers! > Rich >
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Assuming the plastic is something like PE, a hot wire should cut them effectively. If it's rigid PVC rather than PE, it might kill the operator as a side effect.

Best regards, Spehro Pefhany

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Spehro Pefhany

A small electric chainsaw works like a charm, and any flaws can be filled in with spray foam before the pour. There is absolutely no wear on the tool (even if it was useful for something else, which it isn't). If you really want an artistic cut, then one of those electric carving knives that you sometimes see at garage sales might do the trick.

Ken Muldrew snipped-for-privacy@ucalgazry.ca (remove all letters after y in the alphabet)

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Ken Muldrew

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