4 motor Hot Wire Cutter

So there’s three major parts: hardware, firmware, and software. Hardware could be done like this:
https://www.instructables.com/id/Make-a-CNC-Hot-Wire-Foam-Cutter-from-parts-availab/
With two 2D gantries on opposite vertical faces of a box. A hot wire runs between the two gantry heads.

I would probably use Makelangelo-firmware, add a few commands to heat the wire. one gantry would use X and Y values for position. The other would use U and V. This way the wire could make angled cuts.

The real challenge is the software. Personally I’d start with 2D cuts where U=X and V=Y all the time, because that would be easy to calculate. I fail to imagine how to cut, say, a plane wing. There’s probably a clever way to take a 3d model of a wing and extrapolate the “shadow” on each box face, such that following the shadow edge cuts your wing profile.