Devlog #4 - Main Base Redesign + Torque Up & TPU Gripper Redesign

First of all, thank you all so much for the support on my last devlog, it means a lot.

In my last devlog I discussed either getting new servo motors or torqueing up my current motors, and I went with the latter. I have redesigned the main base of my gripper arm & added more gears to torque it up, with only a basic 2 gear ratio. The CAD of this was horrific to make and also looks horrific, but at least its functional? (Hopefully)

I also redesigned the TPU gripper by adding a multistable structure. “Multistable” just means it has more than one stable state, with the idea being that as the gripper closes, it has an easier time squishing into the second state.

I will soon reprint the gears and main base and build it soon. Assuming it works as intended I will probably add a pressure sensor, work that into my code, and then ship it. Only if this works though…

Thank you so much for the recent support once again!

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!

Devlog #2 - Robotic Gripper Arm Build + Wiring

You can check my first devlog to understand what I’m building and the CAD behind it.

I printed all the parts with PLA and the gripper arms with TPU, and assembled them. Something I forgot to mention in the first devlog is that the assembly doesn’t require any screws (besides the ones that come with the servos), and all attachments are printed pegs that create friction fits.

I first started by wiring one servo and just making sure the gears and movement works properly. I did have to fix the gears as they weren’t meshing properly, so I increased the pitch diameter by .5 mm. The servo kept browning out and wasn’t able to move both arms a lot, then I remembered that I created it for two servos.

I wired everything up and this is what I have so far!

Currently, my main issue is that its not really holding anything well. I realized that with us humans we dont just move our fingers but we also hold pressure down to make sure any object we hold doesn’t fall, so I’ll need to figure something out.

Any critiques, comments, or concerns would be much appreciated, so feel free to comment down below. Thank you!

Devlog #1 - Robotic Gripper Arm CAD

Hello! I am currently working on a robotic gripper arm that, when finished, will have TPU arms, be powered by an Arduino, and have a pressure sensor to carefully grab whatever object it’s trying to grab.

I have spent the last couple of days making each part in Onshape and making an assembly, which is shown by the GIF (which I dont think works for some reason, quite sad). I started with a basic servo model, which I created a case around. I next added a gear attachment to the servo, which also connects to the handle of the gripper. Once I connected all those parts on the assembly with revolve mates, I worked on the lever thats directly connects the base to the handle, which I then added to the assembly (with only a couple modifications that messed everything up.)

Overall, I am quite happy with this current model, and I will start printing the parts soon and work on assembly of the mechanical aspect of this build, and make any adjustments on the CAD if necessary. Excited to see this build in real life!