A quick parametric gearbox generator, upgraded to support helical spur gears. 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.
As with previous post, this is tested. 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.
NOTE: Files to print are HelicalGears.stl for the gearing, and NoGears.stl for the other bits of structure (planet carrier, top and bottom plate).
The main reason behind this was to find out if helical gears are quieter or not. Turns out they're not really, at least with the twist I have on them. Not sure it's worth it for the extra difficulty involved in assembly! Might be as well sticking with https://www.thingiverse.com/thing:2410859 although this scad file generates the same models if "DblHelixTwist" is set to 0.
Small update: Have compared the two gearboxes more carefully - at ~150 RPM input, the helical model is definitely quieter than the straight spur-gear version. Plan to test a DblHelixTwist = 80 version next.