This Inverted Cycloidal Drive Is Perfect for 3D-Printed Robots

3D printing was originally intended for prototyping and as far as it has come in the last 45 years, it still has limitations when producing functional parts. Heat and mechanical wear are particularly problematic. That’s especially true for robotics actuators that integrate gear reductions. To work around those limitations, Mishin Machine inverted the typical cycloidal drive arrangement to suit 3D printing.

A normal cycloidal drive is already ideal for 3D printing, because it offers great gear reduction in a compact package and minimal backlash, without requiring high precision or tight tolerances. But if you don’t build them with bearings on the rollers, they will wear through 3D-printed plastic in short order. Bearings get expensive, so it would be nice to use fewer of them and that is exactly what Mishin’s drive accomplishes.

This is basically a cycloidal drive, but turned inside-out. Instead of an inner cycloidal disc with an eccentric shaft and a separate pin disc, it shuffles the whole arrangement around. Now there three outer cycloidal discs and no eccentric shaft, because the cycloidal discs (now plates) are eccentric relative to each other.

This could be easier to integrate into a greater design and it is also very easy to 3D-print. It still needs bearings on the input and output shafts, but doesn’t have rollers that need bearings. It just has steel dowel pins, which are dirt cheap.

You should be able to build this complete “three ring” cycloidal drive for less than $5, which is pretty fantastic. And based on Mishin’s demonstrations, it seems to perform very well. If you use OnShape, Mishin has uploaded models and created a script to help with your CAD work when using this drive (links are in the video’s description).