While there are all sorts of ways to build a hot wire foam cutter, this design from [jasonwinfieldnz ... It stretches as it heats up, and shrinks as it cools back down. The interesting part ...

[Elite Worm] built a hot wire foam cutter that can cut any type of foam with ease, be it Styrofoam or grey craft foam. There are a ton of ways to heat up a taut piece of nichrome wire, but few of ...