Planetary gearbox

A sun gear, orbiting planets, and an internal ring.

A planetary (epicyclic) gearbox puts a sun gear at the centre, several planets orbiting it, and an internal ring around the outside — a compact, coaxial reduction. The generator enforces the epicyclic relations (ring teeth = sun + 2×planet, the equal-spacing assembly rule) and phases every gear so the teeth interlock. With the ring fixed, the sun driven, and the carrier as output, the reduction is 1 + ring/sun. The gears are separate bodies — print the sun, planets, and ring and add your own carrier.

1. Open the Generate panel from the left sidebar and choose Planetary (under Gears & drives).
2. The sun, planets, and ring drop in meshed and phased, with the reduction shown. The parameters open in the Properties panel, where you set them.
3. Set the sun and planet tooth counts and the number of planets.
4. Set the shared module, pressure angle, thickness, bore, and ring rim width.