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: is that tolerance normal? Will grease help to reduce it? has anyone tried it? If I need to change that plastic piece - where can I find one? StepperMotors? This is the drawing board: I'm using the design of Ricard odeazambuja: