Foam cutting needs very little force, so the motion system can be light and cheap — but it must be repeatable and keep the wire straight and tensioned.
Stepper motors
NEMA-17 stepper motors are the standard — the same motors that move 3D printers. They move in precise increments and hold position without feedback. A foam cutter typically uses one per axis (4–5 motors). NEMA-17 has ample torque for the tiny loads of moving a wire end on belts.
Stepper drivers
TMC2209 drivers are popular: they are quiet (smooth current control), support sensorless homing, and protect the motors. Older A4988/DRV8825 drivers also work but are noisier. The driver sets the motor current and the microstepping (smoothness). One driver per axis, plugged into your control board.
Linear motion
- MGN12 linear rails — smooth, stiff, low-friction guides for each tower axis. The nicest feel.
- Smooth rod + bearings — the budget alternative; perfectly usable.
- GT2 belts — toothed belts convert motor rotation to linear motion. Add spring idlers to keep them taut and backlash-free.
Wire tensioning
The most foam-cutting-specific part of the motion system. A hot wire expands and goes slack, so a spring-loaded tensioner (or a sprung tower) pulls it taut even when hot. A straight, tensioned wire is the single biggest factor in cut accuracy — budget for good tensioning.
Steps/mm calibration
Each axis needs its steps/mm set so a commanded millimetre is a real millimetre. It depends on motor steps, microstepping and belt pitch/pulley teeth. The practical method: command a 100 mm move, measure the real travel, and scale the steps/mm by (commanded ÷ measured). Repeat per axis. Get this right and your parts come out the size you designed; get it wrong and everything is proportionally off.