A project log for 3D Printed Robot Joint with Active Compliance

A general purpose robot joint using a cycloidal gearbox and an ODrive modified to support active compliance

tim-wilkinsonTim Wilkinson 07/11/2019 at 21:272 Comments
While doing some testing last week, the joint I was experimenting with suddenly jammed up; it wouldn't move at all. Disassembling it I found this:I don't begin to understand where the load and stresses on this design are, but clearly there's quite a bit on the pins, and while they're made of metal, the cycloidal disks are just plastic. So this part needs to be reprinted with more infill and an increased number of perimeters. I originally just used 20% infill and 2 perimeters, so I'm going to up that to 50% and 6 and see how they new disks survive.


paulvdh wrote 07/15/2021 at 03:04 point

I don't believe the cracked cycloidal disk has much to do with any load.

It almost certainly is because of the hole for the bearing in the center was too small, and pressing it in causes permanent stress in the cycloidal disk.

The big hint is the wide gap in the crack.

That gap shows how much the plastic was stretched when the bearing was pressed in.

  Are you sure? yes | no

Paul Gould wrote 07/18/2019 at 15:34 point

How much load were you putting on the joint? Only 3 pins actually transfer the torque per gear. If you don't like bearings or bushing why not try larger diameter pins. eg 5-8mm.

  Are you sure? yes | no