Tutorials and resources for 3D printing and 3D modeling enthusiasts

3D Model 03: 3D-Printable Multi-Stage Planetary Gear Mechanism


This is a fully functional hand-cranked model of a multi-stage planetary reducer. The photo below shows this model with 3 stages. Each stage has a gear ratio of 1:6, so the overall gear ratio of a 3-stage reducer is 1:216.

Click to download these .STL files


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1.73 MB
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Additional Notes

The design allows for an unlimited number of stages. However, for a hand-cranked model, the practical limit is 3 stages. Even with feverish cranking, the output shaft barely moves because of the very high gear ratio.

You need to print:

--- PER MODEL---
1 front
1 handle
1 shaft

--- PER STAGE---
1 ring
3 planets
1 carrier
1 sun
6 washers

2 Metric Phillips-head countersunk M3-12 screws PER MODEL
2 Metric Phillips-head countersunk M3-12 screws, and 2 Metric M3 nuts PER STAGE

Assembly Instructions:

  • Attach sun to the bottom side of carrier with two Phillips-head M3-12 screws and two M3 nuts (available cheaply on eBay.) The hexagonal holes in the sun should be pointing outwards.
  • Mount 3 planets onto carrier, secure each with a washer.
  • Insert the carrier with the planets and sun on them into ring. The sun goes in first.
  • Attach ring to front (for stage 1) or to previously installed ring (for stages 2, 3, etc.) The sun needs to be pushed hard into the following stage's planets.
  • Secure the ring with three washers.
  • Once all stages are assembled, insert shaft through the hole in front. Push hard.
  • Attach handle to shaft and secure with two M3-12 screws.