[Frank Herrmann] had an interesting idea to turn a geared DC motor into a servo ... has a weight and torque advantage over a NEMA 17 sized stepper motor, but we see no hard data on accuracy ...

Interfacing a shaft to a 3D printed gear doesn’t have to be tricky ... come in sizes specifically designed for common stepper motors like NEMA 17 and NEMA 23. Ironically, these couplings ...