The gearbox design in its current from is absolutely not recommended for reproduction. Don't think this is something you can print and build in its current state.
1) it takes extensive calibration and likely a second try to get the parameters dialed in (-50 µm on internal and external surfaces, properly adjusted extrusion ratio for the filament in use, random layer starts to avoid asymmetry, probably lowered speed to avoid surface artifacts)
2) Incoherent mix of fasteners, embedded nuts, heat set inserts, PH and hex head screws, countersink screws, machine bolts.
3) At least in this model, the straight section on top of the sun gear greatly interferes with the surrounding helical profiles, making assembly/disassembly a hassle, potentially damaging the teeth and creating plastic debris.
4) Why are there no vents? Allegedly the design is supposed to be greased up and then closed. I disagree, that's a terrible idea. Now, I ended up filing all the teeth in an attempt to get it to run more smoothly (didn't help much), but there is merit in running the gearbox dry for a while to wear down irregularities. During this operation, the dust should be vacuumed out every now and then, followed by a final disassembly, brushing to clean, and then re-assembly with grease.
5) The front flange has 5 countersunk screw holes (= screws not intended for mounting) and no holes for heat set inserts. You can use this gearbox as a paperweight, but you can't immediately mount it somewhere.
6) Front flange has no relief for the bearing seal and inner race, so when the bearing is installed, it rubs. Same goes for the inner thin section bearing.
7) No bevels so it's more difficult to get the bearings started when pressing them in.
8) The most important part, the transfer of torque through the planets to the output flange is messed up. The tiny, fragile bearings sit loosely on M3 screws, so they get bent around. The screw threads will wear down, creating more opportunity for wear, jamming and eventual failure of the screw connections. A better way to do this is to press the bearings onto precision ground dowel pins. This supports the inner ring and allows the planet gears to be supported through a cage on both sides, significantly reducing the bending motion. Similar constructions are seen in cordless drill gearboxes, and even inline skates use shoulder bolts or sleeves, and two bearings with some spacing.
9) No vents also means you can't add e.g. a 5015 radial blower to cool the motor. The slots in the back are cosmetic and not designed to allow air flow through the motor.
10) The BOM is incomplete and the original creator put it in the description of their youtube video so they could get you to use *mazon affiliate links.
20x27x4 Bearing : 6704-2RS
3x10x4 Bearing : 623ZZ
45x58x7 Bearing : 6809-2RS
5010 Brushless Motor (I picked 5010-360KV)
M3 Locknuts
M3x5 heat set inserts
M3x16 Cap Screws
M3x6 Cap Screws (motor mount)
M3x20 and M3x30 were also used, the latter to be able to force the M3 embedded nuts down their deep pockets.
Share your story if you too fell for this design. Cheers.
