Electrical Q; Building a foam cutting hot wire.

[BRENT in 10-uh-C]

I need to build a 'hot wire' to cut some urethane insulation foam. I need a rheostat to cut the voltage to the wire, and my question is, can a 120v household light dimmer switch be used inline with a 12v battery power source to cut the voltage to the wire?

 

[oilslick]

I want to build one too.

 

[MBfreak]

If you can find an old style battery charger with just a step down transformer and a rectifier it will probably work well.
Modern chargers with chopper electronics and voltage/current profile contrl will not work, all I have seen requires that the "charging object" has a voltage .

Ola

 

[sberry]

Yes, old charger and 035 stainless mig wire maybe? Need a manual charger. May be able to use a welder if you can go low enough. One of those old ****** welders plugs in to 120v.

 

[wolfhawk73]

http://www.jacobs-online.biz/nichrome/NichromeCalc.html

Use nichrome wire and the calculator in the link to see what kind of power you might need. Plug-in transformers that are used for routers, phone chargers, child's toys' battery chargers, etc, can be used as a power supply.

There are some decent tutorials on youtube, of course.

 

[pstnbly]

I don't think you are going to have much luck cutting urethane foam with a hot wire. Hot wire cutters are used for expanded polystyrene, they even have trouble cutting extrudes polystyrene. Urethane foam is much more heat resistant.

 

[rburke65]

I built one to cut expanded foam....styrofoam......with a dimmer and ? some kind of steel wire that a buddy gave me. Worked well. Don't know about your urethane via,. Sorry.

 

[nehog]

... my question is, can a 120v household light dimmer switch be used inline with a 12v battery power source to cut the voltage to the wire?

No, you can't use a 120 volt light dimmer.

 

[rockettgpw]

I have used a 240v (Aust.) to 24 v transformer used in low voltage hvac controls connected to nichrome resistance wire, ran the wire through a hole in my steel bench up to a spring hanging from wood fixed to the shelf above. Alligator clips from tx to cutter wire, one connected under the bench and the top one on the wire can slide up and down to vary the resistance and therefore the heat. You will fiddle a bit to get the tension and heat as you need.

You can find resistance wire in old heater elements or rotary style variable resistors. some electronics shops will sell it in small packets.

If a wire cutter dosen't work you could try an old electric bread knife.

 

[n20junkie]

One of the best threads for what the OP seeks. My version is posted as well among lots of good info.

Get the nichrome wire. Stainless safety wire works, but is too low of a resistance and it will overheat the transformer.

https://www.ar15.com/forums/t_3_4/292695_.html