This is a saw-style tool for hot-wire foam cutting (NiChrome wire sold separately).
WIP: The edges need to be moved a bit further from the screw holes, my first print started to tear in a few places after I put in the screws.
I'm still experimenting with the power source. A 5V 1A USB wall wart, gets it hot enough for a slow cut. 6.5V from a pack of 4 AAAs seemed to do the trick, but it didn't last as the pack's voltage dropped pretty quickly.