Stackable planetary gearbox for NEMA 17

Hi everybody!

Here is a fully printable, without any support, stackable planetary gearbox made to fit NEMA17 type motors.

You can stack as many stages as you want. With a 1:6 ratio, the speed will go down quite quickly, but the torque will increase as well :)

I tested it with three stages, giving a speed reduction of 216, but a torque of 140 Nm (mechanical losses not taken into account) with a 0.65 Nm NEMA 17. It's a huge torque!!

With three stages stacked, you can block the output shaft, everything resist, no teeth broken ! It's the motor that will get stuck :) This is thanks to the bearings, the screw, and the part size.

The last stage is slightly different from the intermediate stages, since you don't need the sun anymore.

Parts to print:

For every stage (intermediate or final), you need to print:

• 3 x Satellite.STEP 
• 3 x Goujon.STEP 
• 1 x Porte_Satellite_Bas.STEP 
• 1 x Couronne.STEP

For the intermediate stages, you need to print:

• 1 x Bloque_Porte_Satellite.STEP 
• 1 x Porte_Satellite_Haut.STEP

For the last stage, you need to print:

• 1 x Porte_Satellite_Haut_output.STEP

Additionally, you need to print:

• 1 x Support_Moteur.STEP 
• 1 x Sun_Gros_Moteur.STEP

Print Settings:

Avoid printing the parts in PETG. If it looks good from the resistance point of view, it's bad from the friction and details point of view. I recommend printing all the parts in PLA, with at least 3 perimeters. (It's the number of perimeters that will give the strength). For the motor support and the sun, you might have to deal with the heat coming from the motor. Personally, I printed these parts in PC. For the tooth, place the seals on the edge of the tooth. It makes it easy to remove after the print and gives a smoother motion!

Additional mechanical parts:

For each stage, you will need:

• 3 x 625 ball bearings (planets) 
• 1 x 6809 ball bearing (planets carrier)
  • Mind that inserting the ball bearings is quite tough, it's on purpose! 
• 3 x M3-16 cross-head screws (to hold the planets) 
• 9 x M3 Nylock nut (planet holder and link to the next stage)

 I use silicon-based grease to make the motion smoother.

Enjoy :)