This compound planetary gearhead is an anti-backlash version of my earlier Robot Actuator (smallest version): https://www.thingiverse.com/thing:3293562 It has about 50% more torque, significantly less backlash, and also runs more smoothly. It is designed for a 35mm tin can stepper, and requires 35 4mm (or 5/32") balls for the integral slew bearing. It also has a 38.4:1 reduction ratio.

When printing small gears, even on a well tuned printer, the printing irregularities end up being significantly large compared to the tooth size, and produce a lot of friction. You can increase the clearances in the gear design to reduce friction, but then you end up with a lot of backlash. My solution here is to make the ring gears flexible in the radial direction but stiff torsionally. This springiness takes out the backlash and also allows the ring to expand to accommodate irregularities in the tooth profile.

When I get more time, I'll also do anti-backlash versions of the medium and large actuators.