25 : 1 · two 5 : 1 stages

Two 5 : 1 stages for slow, strong stepper output.

Stepper gearboxes25 : 13 planets2 stagesRing held

Build it with your AI

Using the CheapCADTools connector, design a 25 : 1 planetary gear set in Planetary Gear Designer: module 1 mm, 20° pressure angle, herringbone teeth, an 18-tooth sun, 27-tooth planets and a 72-tooth ring, three planets, a profile shift of 0.2 on the planets, face width 8 mm, two stages stacked. The sun: a 5 mm bore with a D-flat 0.5 mm deep. The carrier's output: an 8 mm bore. Set an input torque of 0.45 N·m. 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 Ø20.62 mm · face 8 mm · bore Ø5 mm D-flat (0.5 mm flat) · no hub

Planets · 3

27 teeth · shift +0.2 · tip Ø30.34 mm · face 8 mm · bore Ø5.3 mm on a Ø5 mm pin · print 6 (3 a stage)

Ring

72 internal teeth · shift −0.4 · outside Ø88.11 mm · rim 5 mm below the roots · one ring round both stages, 27.5 mm long

Carrier

straddle (two discs and posts) · disc Ø72.34 × 5 mm · 3 pins Ø5 × 19.0 mm · output bore Ø8 mm · plus one carrier printed with the next stage's sun

The set · Module 1 · 20° · herringbone

25 : 1 reduction in two 5 : 1 stages: the ring is held (one ring round every stage), the sun is the input, each carrier drives the next stage's sun and the last carrier is the output.

Notes

Hardware: 6 × planet pin Ø5 × 19.0 mm; 6 × M3 screw, about 11 mm long.
2 stages, one under the other: each carrier but the last carries the next stage's sun on its underside, one part; print it sun down, with supports under its disc.
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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