Summary ------- Revision of "Planetary Gearbox for Nema 17 Stepper" (https://www.thingiverse.com/thing:2172314) by lasdasdas (initial "Compact Planetary Gearbox" by raldrich). The ratio is inverse to increase rotational speed of stepper, Ratio is about 1:5. The gears are updated to reduce tolerances and increase ratio based on "Getriebe Bibliothek fuer OpenSCAD / Gears Library for OpenSCAD (http://www.thingiverse.com/thing:1604369) by janssen86). The case has now MEMA 17 standard measures (42mm square, cut corners). The sun gear has a M8f0.75 thread (ISO Feingewinde III, DIN 13-4) to attach chucks, collars or similar. Glue the sun gear axis ur use a nut to fix it on bearing. I glued the "Gear3-MotRing.stl" under the lower planet holder. You will need a part of each *.stl and 3 of the "Gear3-PlanetGearXS.stl" to make a whole gearbox. Some parts needs to be turned for printing, such as the upper planet holder. BOM (non-printable parts) ------------------------- Planet holders: 3x M3 nuts 3x M3x14 screws (socket head cap, hex key, DIN 912) Case fixed on stepper: 4x M3x30 screws (socket head cap, hex key, DIN 912) Sun gear: 1x Bearing 688ZZ (8x16x5), to hold sun gear axis 1x (optional) M8f0,75 nut to fix sun gear axis Finishing, assembly ------------------- After the print, sanding was necessary for some parts but the gearbox works overall as expected, I didn't test it at maximum torque yet but it looks promising. Depending on slicing and printing, tolerances can vary. To adjust this issue play with the diameter of the planed gear. The included gear is about 98% of the original diameter from the gears library to reduce friction and to increase smoothness.