Planetary Gear Snowflake

The model

The gear has 18 teeth on the sun gear, 9 on each of the six planets and 36 in the ring gear (module 1.25, involute teeth with 25° pressure angle). If you hold the ring still and turn the sun gear once all the way around, the planets travel one third of the circle and spin on their own axes. A dot on each planet and the hexagon in the sun gear make the rotation visible.

All gears have herringbone teeth (30°). This keeps them together without a cage or cover: axially the gears have about 0.5 mm of play and cannot be pushed out further. Between two tooth flanks there is 0.4 mm of air in the print position. The motion is calculated in 55 rotation positions over a full turn of the sun gear, with no contact.

The sun gear stands 1 mm proud and has a thumb recess with a hexagon. On the outside the ring gear carries six branched snowflake arms and six short intermediate arms as a grip. It is printed in one color; in the function picture the gears are only colored differently for explanation.

View print notes (German)

Print notes included in German; part names are self-explanatory.