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How to make hot wire foam cutter?


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#1 NozomiWhiteWolf

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Posted 20 January 2006 - 06:00 PM

There are only a few sites on it--I used one over the summer at Worcester Polytechnic during the "build a glider plane" contest. It was made out of a pipe in the shape of a bow and the 'bowstring' was pretty much a wire stretched the length of the pipe and attached at either end. There were two alligator clips supplying electric power to the wire and heating it up... and to cut the foam, you had to put wood or something hard (cut in the shape you wanted the foam to be) and use that as a guide for the foam melting wire.

This is the only site I could find: (http://www.gizmology.net/hotwire.htm)  but it's for making a giant scale one. I want a smaller one (not sure of amt of power to use for the electricity? on that website it says:

Quote

Power is provided by a 120V to 12.6V 3A transformer. I tried a door bell transformer (16V, no current listed) but it just didn't have the oomph to heat the wire. This transformer will heat the wire red hot if you let it - a light dimmer keeps it in check. (Note: 120V can kill you.)
)  because I need to cut a GIANT piece of pink foam (about 8ft tall or so) to make a giant knife for my buddy's pyramid head costume.

If I can get this foam cutter built, I can make a WIP thread for the fiberglass sword. :)

Anyone ever make one/use one before?

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#2 Reisel

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Posted 20 January 2006 - 06:26 PM

While I have never personally used one, my husband has this hot wire foam cutter.  It's not that big.

Attached File  wondercutter.jpg   33.61K   140 downloads

I don't know where he got it, probably at a craft store.

#3 NozomiWhiteWolf

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Posted 20 January 2006 - 06:43 PM

Reisel, on Jan 21 2006, 12:26 PM, said:

While I have never personally used one, my husband has this hot wire foam cutter.  It's not that big.

Attachment attachment

I don't know where he got it, probably at a craft store.

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Hmm...probably works under the same principle...is it battery powered?

I need a HUGE one so I'm probably going to have to make it myself.  <_< I just don't want to get electrocuted in the process and I wondered if anyone had tips on building them (or cutting corners/dos and donts, etc.)...?

If it all boils down to not being able to make it I can just buy one if they sell them any bigger.... :)

#4 Reisel

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Posted 20 January 2006 - 07:02 PM

Yes, it uses 2 D batteries.  It's pretty simple.  It's a cardboard tube to hold the batteries, a spring, two metal caps on the ends, and of course the wire.  

Just because I wasn't doing anything else, I did a search for the thing and found this site mentioned too.  http://www.hotwirefo...stomer/home.php  Very fancy.  They're kind of expensive though...

#5 NozomiWhiteWolf

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Posted 20 January 2006 - 07:47 PM

Reisel, on Jan 21 2006, 01:02 PM, said:

Yes, it uses 2 D batteries.  It's pretty simple.  It's a cardboard tube to hold the batteries, a spring, two metal caps on the ends, and of course the wire. 

Just because I wasn't doing anything else, I did a search for the thing and found this site mentioned too.  http://www.hotwirefo...stomer/home.php  Very fancy.  They're kind of expensive though...

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Thanks, Reisel. I'll look into those. :)

#6 telemarq

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Posted 20 January 2006 - 10:20 PM

NozomiWhiteWolf, on Jan 20 2006, 07:43 PM, said:

I need a HUGE one so I'm probably going to have to make it myself.  <_< I just don't want to get electrocuted in the process and I wondered if anyone had tips on building them (or cutting corners/dos and donts, etc.)...?
The biggest "do" I can suggest is have plenty of ventilation and a respirator when you finally use it. You are basically burning/melting plastic.  That can be toxic. :(

#7 Guest_Ragnarok043_*

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Posted 21 January 2006 - 02:23 AM

since you'll be using a DC power source you dont really have to worry about getting electrocuted, but if you're really worried you can always add an inline fuse.

#8 Guest_sprtrooper_*

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Posted 21 January 2006 - 06:47 AM

Go with Rag's suggestion. I m not sure what the ratio would be but the thickness of the wire with too much power running through it is what causes the wire to heat up. You dont' need that much power to warm up a really thin wire. Have extra on hand and dont go too fast, in case the wire breaks and to prevent it in the first place. This will be toxic. Why not use a small saw and then place poly strips/fiberglass on after to smooth. Then you only worry about the poly fumes and not the electricity.

OK people it only takes one volt at one amp to kill you. The battery set-up is good because it doesnt have much amperage. I've seen someone get shocked with a 120 AC volts and live, but it was a floor buffer, those things dont need a lot of amps. A tv that was off for 1/2 hour could still lay you out if you touch the capacitors. You ever run a amp meter on the tv wire before turning it on. It takes like 25 amps just to start them. Goes down after but the capacitors increase and maintain the power.

#9 NozomiWhiteWolf

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Posted 21 January 2006 - 01:05 PM

Thanks for the replies.

@ Telemarq: Don't worry, I've cut foam before and it does stink...I've never worked with fiberglass before but I trust my dad will help me out a bit and I DO own a respirator from Lowes.

@Rag: Thanks, I'll talk to my dad about it. :D

@sprtroopr: I've never worked with ANYTHING electrical in the least bit (much less built anything) before so how would I know what would kill someone?  ;)

#10 Honeycakes

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Posted 21 January 2006 - 04:30 PM

I actually just picked up a small hot wire cutter from Micheals. It cost 19.99 and it works well. It is an electric version and plugs into the wall, it has an on/off switch.

It heats up VERY quickly and cools just as fast. The only thing I would worry about is the Type and Denisty of the foam that you are going to use.

I have used it successfully on reg packing styrofoam and some of the higher density foam. (the high desity foam is a lot slower to cut, you pretty much let the wire melt through at it's own pace.)  While the regular foam is more like a hot knife in butter.

Flower foam and dry foam are a toss up some will work with the hotwire cutter and others simply will not. I have bought large foam blocks online from different places and some work and some don't it is a mystery too me. They are both versions of the dry flower foam....so be careful when you order foam. Check with the website if it can be cut by hotwire or if they recommend a regualr saw. (Which is Hell)

I can also recommend this stuff Foam Putty It is a AMAZING to work with. Covers and smooths out everything....and you can sand and paint on it as well. I wish it came in a larger tub though. I use it on all of my custom bases and I sculpt a lot with it on a regular basis.

Michaels also sells a foam specialized paint series in basic colors that also can be used to smooth the surface before you airbrush (this is in the foam section next to the wire cutters). But nothing compares to the miracle of the Foam Putty.

Here are some sites that I look at one is Styrofoam Tips and the other is a foam prop studio they answer e-mails with questions or so I have been told. FoamProps

#11 redrage

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Posted 21 January 2006 - 05:02 PM

I made mine in 1990 with a second hand 1950's Lionel train controller and some inconel wire. Don't know if you can find those transformers so easily anymore.

You can get blue foam from a vault manufacturer and you can treat the edges with drywall compond. Use Gesso to finish it when you are done.

It gives off cyanic gas when you cut foam; this is highly toxic.

Hey it got me through grad school...

#12 Guest_sprtrooper_*

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Posted 21 January 2006 - 05:13 PM

One of the perks of my job in the service. I know most people dont know how much can hurt you, thats why I said it. Someone could think, this is only one volts, but if it has amps behind it... lookout.

I was saying it in general b/c someone may read this and hook up a regular 120 v AC line to a line and wind up hurting themselves or worse. It would be irresponsible of the posters not to mention the danger involved with an open live wire.

Later and good luck.

#13 winged

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Posted 21 January 2006 - 08:17 PM

here is a good  description of a hotwire build.  If you do a search at that forum you can find a lot of info about building hotwire cutters.  IE, how to tension the wire, where to get the wire, and so on.  A lot of the cutters described on that forum are designed for use with templates.  By that i mean they are tapeing or glueing thin plywood templates on both sides of the foam to be cut.




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