A quick parametric gearbox generator. Use a separate program to combine components if you want to print them all at once. This is NOT a print in place!
I used ReplicatorG to shift all the models to the print bed and flip the top cover plate, then blender to combine all the models into one file for the print.
Now tested, and minor fixes applied to scad file. The included stl files are for the NEMA17 gearbox with which tests were carried out. It was found that it prints with a 0.4 mm nozzle, but it helps to run the gearbox for a period of time with some autosol chrome polish to aid working-in. Once it's sounding quieter, clean and grease before reassembly.
Hardware required for generated models: 3x 3mm dia.~ 18 mm shafts for the planet gears. M3/ ~20 mm screws to affix to NEMA17 motor. Also, it helps to add 6 washers - one above and one below each planet gear to separate them from the carrier.
Updgraded to allow fishbone gear generation: https://www.thingiverse.com/thing:2415838