crafty dudes- d.i.y. tools - hot wire cutter tech?

[praisethelowered]

Has anyone ever built a "hot wire" cutter for cutting foam. I need to cut a raiused edge on a bunch of foam and seem to remember this being the hot ticket for production sytle foam shaping. I have a few immediate O.T. uses but ultimately it will be for bucks for some fiberglass work.

[Tuck]

I would like to build one too if anyone has any info on making one?

Tuck

[slazzen]

it is pretty easy I built one for a mold making shop i worked for I used a power supply like for a train or tattoo machine whith a reostat a flat table and a frame to make the wire moveable then you make metal templates to trace while you cut

[praisethelowered]

More details man- your like teasing us.

You need DC power? How about a car batery? Or a trickle charger?
What makes the wire hot?
I was thinking of using thicker steel wire so that I could bend it into a curve and it would hold the shape as I pulled it through the foam. Will that work? The one I saw before had a thin wire that was stretched between two points for rigidity but it wwouldn't cut a shaped edge for the same reason.

[59Rocket]

I've used one but can't remember how it was assembled! http://www.jalopyjournal.com/ubbthreads/images/graemlins/frown.gif

[Mojo_AL]

As simple as it gets. All you need is something to hold the wire, a way to put tension on it and a power source. Use low voltage dc.

I've tried an electric train transformer, but you could use a doorbell transformer or a car battery or battery charger. Anyways, you need a way to vary the voltage to get the wire just hot enough but not too much. You could probably use a car light dimmer for this.

As for the wire, I used small guitar strings. I remember reading that some better wire could be found but guitar strings will do. Ordinary steel wire won't do, something to do with the tension that will change with heat, if my memory serves me right.

Keep in mind that polyeurethane foam can't be cut with a hot wire. Use polystyrene or something like that.

Here's a simple drawing of my cutter.

good luck!

[dusty]

I believe the wire used in cutters is called Nichrome(sp). Its made to handle the heat.

[praisethelowered]

I need to cut a curved shape - will a fatter stiffer wire that can hold it's own shape work?

or will it not provide enough resistance to get hot.

or when it gets hot will it loose its shape?

[uncleAud]

find and old electric oven or stove element...take a hammer and mash all the gray coating off of it..what you have left is a piece of niachrome wire that will take any heat you can give it...make any kind of holder, run 110 volts through a reastat switch and have at it..used to make them for shop class when the school budget was low...they worked great

[sawzall]

[ QUOTE ]
I believe the wire used in cutters is called Nichrome(sp). Its made to handle the heat.

[/ QUOTE ]

dusty is right.. I have a commercial (well ok a hobbist) version of a wire cutter I can shoot a photo of for you.. dont know how its assembled as I havent ever used it yet.. still new in the box..

[Rix2Six]

Model Airplane buidlers have been doing this forever. Try looking at www.tekoa.com (http://www.tekoa.com)

[deuceguy]

I had to build one for work. I used some kind of 12v power supply and thin stainless steel wire for the hotwire. Not the best stuff to use but we have a lot of it on hand. The spring works well to keep tension on the wire when it heats up and expands. Its important not to connect the power after the spring. If you run a current through the spring and it heats up, it loses its temper and you don't have a spring anymore. Hope this helps.

--------------------
Don't know what I want, but I know how to get it.

[burndup]

Nichrome is correct, but DON'T run that into 110 AC unless you put a current limiter in series... ie, run a 40-60 watt light bulb in series with the wire, maybe put a rheostat on it too...

[Ragtop]

My brother in law builds RC airplanes that way. He used a big model railroad trasformer to cut the voltage way down and a piece of stainless wire from my mig welder does the cutting just fine. You'd need to cut the voltage down somehow whether you use a transformer or a battery or you'd have a dead short. The nichrome wire will provide resistance if you can find it.

[JOECOOL]

I have been useing one for years . I used a piece of 3/8 fuel line so I could bend it in a large C shape,put a wooden dowel in one end for insulation,put a spring on one side ,the wire I bought at a local store that repairs toaster ovens.
I use a 4 amp battery charger and use the spring as my reostat. Closer to the wire it gets more current further away it gets less.

[286merc]

I built and used one for several years when prototyping microwave antennas and mechanicals with industrial grade hard foam. I also carved a flathead engine.

The wooden frame is similar to a buck saw and used a small turnbuckle for adjusting tension. A spring was no good as we needed constant tension. We built several sizes including a 2 man version.

The wire was stainless steel, available in small rolls at Home Depot, etc. I believe it was around 18 gauge.

Power was 120VAC and controlled by a variable autotransformer. These go by brand names such as Variac, Powerstat. Expensive new but $5-20 or so at electronic junk shops and flea markets. You dont need anything bigger than a few amps. Might be able to use a house type light dimmer since they are built for resistive loads.

Nichrome is a resistance wire as used in heating elements but I wouldnt use it in this application. It becomes brittle, deforms under heat and is expensive.