After taking apart a faulty 'hot plate' that would smoke when plugged in, I obtained a length of nichrome wire, a resistive wire used widely in heating elements (such as toasters, heaters, hair dryers). I knew that a hot wire could easily cut through styrofoam, and wanted to make a small tool to allow me to do that.
This project is quite simple. First find a sturdy frame for the tool, keeping in mind how long and how far out you would like the wire to be (this will affect how much area you can cut off at a time). Next, tighten the nichrome wire onto two metal rods (nichrome wire cannot be soldered) and attach the power source to go across the wire; depending on the length of wire used you may need to adjust current until the wire has a faint red glow. That's it!
Front and side view of the tool; the batteries used to power it and alligator clip connections are visible.
For the very little time it took to construct, the destructiveness potential of this tool is simply mind-boggling. With enough power, it can cut through pretty much everything other than metal: paper, wood (small parts), plastic, adhesive tape, rubber bands, etc. Unfortunately I did not have styrofoam to test the effectiveness of the tool in its intended purpose, but I have no reason to believe it would not do well.
The wire is powered with a 12VDC 1A source and is slightly glowing
Powered temporarily by about 12V 30A using a lead acid battery the wire glows a lot brighter
If too much power is applied to the wire, it glows very bright and eventually breaks in half without much fanfare. When cutting items, the wire sometimes attracts residue such as dry salts, which can be removed after it has cooled down (wiping off the wire with a wet sponge (or fruit pieces?) while it is hot also seems to clean it reasonably). If the wire is kept tight, it will straighten itself out when heated to a high temperature for about thirty seconds; if it cools down in a bent form it will effectively stay that way until heated up again.
The hot wire can cut ice easily!
One thing to keep in mind with this tool is that it releases lots of smoke and potentially toxic fumes, particularly when cutting plastic-based items, and thus should be used in a ventilated area.