Here is another take on a 3D printed gearbox, with a rather novel testing procedure.
The files are here...
www.thingiverse.com
I may try to print it later.
3D Printed Planetary Cycloidal Gearbox by Michael_Rechtin
I designed this gearbox after reading some papers online. A video showing the gearbox being built and tested can be found here: https://www.youtube.com/watch?v=IKkw4d7jyu0 More information as well as a hardware list can be found in the description of the video
www.thingiverse.com