Devlog #3 - TPU Gripper Redesign & Rebuild

It’s been a little since my last devlog, and that’s for good reason. At the end of my last devlog I mentioned an issue I had, which was that the servo wasn’t powerful enough to supply a constant force to actually grab anything, and that even if I had a motor powerful enough to do that, it would use a lot of energy. I have been trying to solve this issue with a compliant mechanism.

The TPU in my last design was 72D, which is really hard and not what I was looking for, but it was what I had. I went and bought 95A TPU which is much softer and squishier, making it ideal for this use case. I also redesigned the gripper arm itself so that it will never contact the second arm, so only the TPU parts close in on each other. I also shifted the holes on the gripper to account for this, and adjusted the angle of the gripper so that it closes cleanly.

I have reprinted everything and rewired it, but I’m facing a similar issue. I expected that after the gripper makes contact with an object, the servo will still work, causing the gripper to compact, which would cause the necessary pressure to actually hold the object in place, but it didn’t do that. It seems that the servo just stops running after the slightest bit of resistance, which isn’t ideal. I am currently planning to adding some high friction material on the inside to help with that but I need more effective solutions. My main idea right now is to torque up the servos, but that’ll obviously slow it down and also I’m not sure about the reliability of 3D-printed gears, but we’ll see. Any help would be GREATLY appreciated right now. Thank you!