Planetary Gear Print-in-Place Demo I expect to incorporate planetary gearing into future projects but I wasn’t real familiar with their design. It’s amazing how they work but they are actually quite confusing as you can achieve different output ratios from the same gear set. I created this model as a demonstration unit to better understand how they work by having a physical example to hold.

Size The gears are module 1, both the sun and planet gears have 12 teeth and the ring gear has 36 teeth. Ratio: 3:1 or 1:4

Demonstration If you hold the carrier and turn the sun gear, you get at 3:1 speed reduction. This ratio is a result of the 36 teeth on the ring gear divided by the 12 teeth on planet gears. If you wanted further reduction, you would make the sun gear smaller then the plant gears.

If you hold the carrier and turn the ring gear, you get a 1:4 speed increase on the sun gear. The is because the much larger diameter ring gear is moving faster than the smaller sun gear. The equation works out to be the 36 teeth of the ring gear divided by the 12 teeth of the planet gear plus 1.

If you hold the sun gear and spin the ring gear and the carrier, there is no reduction and it acts like a bearing

Print instructions Designed for a .4mm nozzle, .2mm layer heights, no supports at 100%.

Printed with Protoposta’s High Five Blue(aff.)

Printed on the Muldex rep-rap IDEX printer.

Support and Licensing If you would like to help support more free models, or get permission to sell physical copies of my models, consider joining my Patreon