Needle cutter for foamplates

I hope laser cutter matches the category of my foam cutter the least wrong - otherwise feel free to put it where it belongs!
Since I like to construct and build remote controlled model airplanes mostly from Depron panels, I spontaneously found the idea of cutting these panels with an oscillating needle fascinating - especially since I do not have the greatest talent to cut such panels satisfactorily with a knife ;-)
As there was an unused controller for a 3D printer in the box, I decided to build such a device. Because the device is useless without the appropriate software, I found my way to OpenBuilds Control, as the software modules available there seemed to be an ideal fit for my project. The dimensions resulted from the 1000mm x 500mm panel size to be cut, and after (too) many days of CAD tinkering, the plan took shape: First on the monitor, then in reality! It is a not too complex machine with NEMA17 stepper motors and GT2 toothed belts for the X and Y axis and a T8 spindle with 40mm stroke for the Z axis. Either the needle piercer for the intended Depron-cutting or a felt-tip pen can be used for testing.
The current status is that I have achieved the desired basic functionality, i.e. I can generate gcode from DXF files that will be processed by the machine. The cutting curves in the x-y plane are traversed precisely and at the desired speed, and the tool is raised to the set safety height during positioning movements. Limit switches are installed for all three axes, homing works - but only on the x and y axes, probably because my pre-compiled grbl firmware was intended for a laser cutter, i.e. a two-axis machine. As I said, the machine can do what it's supposed to do, but it's too obvious that I haven't exhausted all the possibilities that hardware and software have to offer - in other words, there's still a lot to learn, and I'm hoping to find some help here.