# Foam Cutter Help



## Revenant (Mar 17, 2007)

I would like to do some hotwire foamcutting, and I've seen mention all over the web of people using battery chargers as their transformer/power source. I have 2 coils of nichrome wire left over from a previous project, and a car battery charger to use as a source. The wire's pretty thin, and was sold as hotwire replacement for train-layout guys so I know it's good for cutting. I don't know what guage it is; one is "Pro Hardware SIG" and has the item code SIGSH135, and the thinner one is "Woodland Scenics SubTerrain" code ST1436.

My question: The charger has 3 output settings; 10amp-6Volt, 10a-12V, or 2a-12V; which setting do I want to use? I don't know the resistance of the wire. Do I need to buy a rheostat/pot to further control the voltage? 

My aim is to put together a tabletop "band saw" setup to run sheets across, and then some smaller hand-held bows to shape with.


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## Liam (Mar 23, 2007)

Hey Revenant, this is exactly what I have been working on this week. Ideally I would like to go with the HWFF, but until funds free up I'm stuck with a home brew version.

My plan is to use an old Mark model railroad transformer to put power across a guitar string that will be held in place on a PVC contraption. The idea came from the guys at Rocket Team Vatsaas, and their plans for it are here:

http://www.vatsaas.org/rtv/construction/hotwirecutter.aspx

I can't answer your questions about using the battery charger unfortunately, but would be curious to hear how that works if you do try using it. My only thought is that, like you said, you'll probably want a rheostat of some sort to control the heat of the wire. The nice part about the train transformer is that the rheostat is built in already.

I hope that helps at least a little bit.


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## Liam (Mar 23, 2007)

Bah! I'm screwing up all over the place today! The correct spelling is "Marx" for the train transformer, not "Mark." Sorry.


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## turtle2778 (Jul 9, 2006)

ookay there are really really cheap versions of HWFF cutters. I think walmart or hobby lobby sells one for like 20 bucks. Granted its not free, but you dont have to "rig" anythign. You can also use a wood engraver for detail work. Just thought i would help you out. I have the HWFF and its great because of the ability to adjust the heat, but i could have gotten by with one of the cheaper ones. It was a gift from my husband. Ill take what i can get.


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## Brad Green (Jul 29, 2004)

I took the easy way out by using a soldering gun. Just remove the soldering tip, replace it with two brass rods (the screw terminals that hold the tip in place make this simple), bent in a "squared" 'Z' pattern, and stretch a thin piece of copper wire tightly between them. When you trigger the unit on, it super heats the wire almost instantly. Nice thing about it, you can always put the tip back on if you want to solder.


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## Brad Green (Jul 29, 2004)

Managed to find a picture of mine if anyone's interested:

http://img49.imageshack.us/my.php?image=0000023it7.jpg


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## Revenant (Mar 17, 2007)

I like the soldergun hack, Brad... I imagine that guy heats up really fast. Tho I'd feel more comfortable with a pistol-grip setup like that if it had a blade element instead of a wire bow... with a bow-type cutter my hand seems steadier with the old "cheese slicer" sort of handle.

Thanks for the input folks, tho as I mentioned the rig I'm most thinking of using the battery charger with is a table-saw sort of deal with a long vertical wire in a fixed position so the slabs can be slid around relative to the cutting element. It gives more uniform 90-degree cuts (or whatever angle you set it for), especially with thicker foam. And I'd just be Happy Clams if I could get it together with stuff I have, without spending any money. Though I'm inclined to agree with Liam, I'm probably going to want to at least add a variable resistor to get some voltage control.


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## Haunted Neurons (Jun 23, 2006)

I use a battery charger for my homemade foam cutter. To get voltage control use a dimmer switch for household lights and connect it with an electrical outlet. Plug the battery charger into that and control the AC voltage going to it with the dimmer. This will reduce or increase the output of the battery charger so you can adjust how hot the wire gets.


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## zeenon (Oct 27, 2006)

I just posted a How To on my site for Hot wire cutters under Misc Props that should help. You can build the electronics for less then $20 if you skip the fancy LEDS and project box. Don't laugh, I've seen people screw the transformer and dimmer to a 2" x 4" and run......

Z


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## dionicia (Aug 4, 2007)

Liam said:


> Hey Revenant, this is exactly what I have been working on this week. Ideally I would like to go with the HWFF, but until funds free up I'm stuck with a home brew version.
> 
> My plan is to use an old Mark model railroad transformer to put power across a guitar string that will be held in place on a PVC contraption. The idea came from the guys at Rocket Team Vatsaas, and their plans for it are here:
> 
> ...


Thanks for posting this. I got a few ideas from the webiste. Using cardboard as a template...BRILLIANT!


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## JustMatt (Jul 13, 2006)

//EDIT

Nevermind. The Rocket Team link finally loaded and I see that I can probably have a larger cutter


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