7 : 1 · one-stage actuator

7 : 1 in one stage: a small sun and big planets, still back-drivable.

Robot joints & actuators7 : 13 planetsRing held

Build it with your AI

Using the CheapCADTools connector, design a 7 : 1 planetary gear set in Planetary Gear Designer: module 1 mm, 20° pressure angle, herringbone teeth, an 18-tooth sun, 45-tooth planets and a 108-tooth ring, three planets, face width 12 mm. The sun: an 8 mm bore. The carrier's output: a 10 mm bore. The ring: eight M3 bolt holes, an 8.5 mm rim below the roots. Check the design, apply any Auto-fix it suggests, then export every part (the sun, a planet, the ring and the carrier) as STEP and STL and give me the download link.

Paste it into Claude, ChatGPT or any AI app with the CheapCADTools connector, and it designs this planetary set with you, checks it and hands you the files. How to connect your AI.

What's in this design

Sun

18 teeth · no shift · tip Ø20.63 mm · face 12 mm · bore Ø8 mm · no hub

Planets · 3

45 teeth · no shift · tip Ø48.59 mm · face 12 mm · bore Ø5.3 mm on a Ø5 mm pin · print 3

Ring

108 internal teeth · no shift · outside Ø131.58 mm · rim 8.5 mm below the roots · 8 × M3 bolt holes Ø3.4 mm on Ø123.1 mm

Carrier

straddle (two discs and posts) · disc Ø108.81 × 5 mm · 3 pins Ø5 × 23.0 mm · output bore Ø10 mm

The set · Module 1 · 20° · herringbone

7 : 1 reduction: the ring is held, the sun is the input and the carrier the output.

Notes

Hardware: 3 × planet pin Ø5 × 23.0 mm; 3 × M3 screw, about 11 mm long; 8 × M3 bolt through the ring.
The Strength check rates spur sets only: helical and herringbone sets aren't rated yet.

The link opens the whole set in the Planetary Gear Designer's 3D view. Change the teeth, the number of planets or stages, which member is held, the carrier, bores or hubs, then download STL, STEP or the carrier's DXF and SVG.

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