THE ANNIN ROBOTICS FORUM HAS MOVED TO A NEW COMMUNITY. 👉
Joint 5 had freedom...
 
Notifications
Clear all

Joint 5 had freedom of 3.5 degrees - is that ok?

1 Posts
1 Users
0 Reactions
511 Views
Avatar of Eyal Friedman
(@eyal-friedman)
Active Member
Joined: 1 year ago
Posts: 2
Topic starter  

Hi all!

 

Finished assembling my AR4 arm a week ago, and ran some tests on it.

I would like to thank Chris Annin for the awesome design!

 

I realized that my fifth joint got surprising freedom (wasn't sure I had it on the first day). The tolerance is around 3.5 degrees (attached below is a video to show it).

I took the cover off a few times to make sure everything is attached properly and it seems it is. The whole build is moving and it seems that the motor's thread got some extra freedom and might worned out.

Few questions:

  1. is that tolerance normal?

  2. Will grease help to reduce it? has anyone tried it?

  3. If I need to change that plastic piece - where can I find one? StepperMotors?

https://anninrobotics.com/wp-content/uploads/2025/08/Joint-5-had-freedom-of-3.5-degrees-is-that-ok-_Video.mp4

This is the drawing board:

https://anninrobotics.com/wp-content/uploads/2025/08/Joint-5-had-freedom-of-3.5-degrees-is-that-ok-_2.avif

I'm using the design of Ricard odeazambuja:

&w=628&h=472&fit=contain&cbg=white&n=-1" rel="nofollow" >
THINGIVERSE.COM "https://www.thingiverse.com/thing:2283391"
BAXTER Robot Elastic Pen Holder by ricardodeazambuja - Thingiverse
Currently (April 2017), I'm a PhD candidate at the Centre for Robotics and Neural Systems, Plymouth University, working with learning (or programming) by demonstration using Spiking Neural Networks (SNN) implemented as Liquid State Machines (LSM). So, I designed this elastic pen holder because it's not so easy to teach a robot to draw using an uneven surface (although we have a paper based on LSM and Sensor Fusion that partially solves this problem). Also, Baxter was not designed to be super precise and its positional accuracy is +/-5mm. Hint: you should be able to reuse the same screws from the vacuum or electrical grippers.If you liked this thing, don't forget to visit my personal website: ricardodeazambuja.comDISCLAIMER 1: use it at your own risk ;)DISCLAIMER 2: Baxter is a cobot, but it is only safe to interact with people (when using Joint Position or Velocity control modes) if a risk assessment is done every time you add a new end effector. So, be careful if you decide to use this pen holder (don't forget about Disclaimer 1).


This topic was modified 12 months ago by Peter Kappes

   
Quote
Share:
Upload your Photo

Please enter your email address to receive your cart as a PDF.