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From: nahshon@dan.haifa.ibm.com (Itai Nahshon)
Subject: Re: Stiraphome Cutting Methods...
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In-Reply-To: filip@alpha.smi.med.pitt.edu's message of 19 Apr 1994 00:25:40 GMT
Date: Fri, 22 Apr 1994 17:13:27 GMT
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In article <2ov8e4$bop@birdie-blue.cis.pitt.edu> filip@alpha.smi.med.pitt.edu (Filip M Gieszczykiewicz) writes:
>Thus spoke cmartin@aol.com (C Martin):
>>A little while ago, I built a styrofoam hot-wire cutter.  I but a 6VAC, 4A
>>transformer in a box with a wire-wound rheostat to limit current and a 4A
>>circuit breaker.  The cutter is a pair of wooden sticks with 30 gauge wire
>>strung between them.  I started with about a 40 gauge magnetic wire but this
>>was so fine, it kept snapping.  It turned out that the 30 guage wire worked
>>fine anyways.  I used it a little to cut styrofoam and found it can cut fairly
>>fast and will do detail work too (in so far as one can do 'detail' work on
>>styrofoam).  The best way to find out is try it yourself.

>    Greetings. I got a 0.5LB roll of 35 gauge Nichrome wire for $4.00 from
>    The Electronic Goldmine a few months back. No idea if they still have it.
>    It was part # G2844 and their # is 1-602-451-7454. This stuff is
>    20ohm/foot (@20C), pretty strong, and lasts quite a few feet of foam.

>    (It's also very useful for that custom resistor you need now and then)

>    Take care.

>    P.S. $4 shipping ($5 outside USA). Outside USA, Can, & Mexico it's
>    $50 min order. Otherwise, $10 min order.
>-- 
>+-->Filip "I'll buy a vowel" Gieszczykiewicz | E-mail: filip@alpha.med.pitt.edu
>| ftp to bode.ee.ualberta.ca and get OLD electonics faq from /pub/cookbook/faq
>| Checkout: ftp bode.ee.ualberta.ca and get file /pub/cookbook/contents. Neat.
>| Making money with CS and spending it on EE, robotics, windsurfing, & dreams.

I use a wire cutter for model airplane wing cores.
The Nichrom wire is too soft for this purpuse. From myy experience
it's impossible to strech it enough to get a straight cut. I (and others)
have better experience with Piano wire, 0.6 to 0.7 mm thick. I use it
with a 12V transformer for about 1M length of wire. Current is in the 2
to 3 amper range. I got the best results with the lowest temperatures
which are enough to cut the foam. A too-high temperature will destroy
the wire.
If weight is not a factor (it is for me) the higher density foams can
be cut with better accuracy.
Do not try to use hot wire on polyurethan foam. Polyurethan emits
poisonous gasses when heated.
The surface resulting from a good cut will have that "hair" on it.
If you want to glue or paint this surface use sandpaper (very lightly)
to remove that hair.
Most epoxies and water based glues can be used on foam. Also useful
are the 3M Super 77 contact cement (spray can) and some of the odorless
cyanoacrilate glues (like Satelite City's UFO glue).

If anyone wants to know more about cutting and using styrofoam try
to ask in rec.models.rc.

Itai Nahshon
Haifa, Israel
nahshon@vnet.ibm.com
 
