I started putting together the AR4 and noticed what seems like a fair amount of play in J2. I think this is from the gears being unloaded or slop in the keyway? I just wanted to see if this amount of play was normal before I continue with the build.
The J2 planetary gear box does list a backlash of 25arcmin in product spec sheet. With the motors powered on and the arm in compression or carrying a load the backlash is not an issue.
Thanks for clarifying and the fast reply. What I figured with it loaded it wouldn't matter much. When I noticed the backlash, I checked the paper spec sheet that came with the stepper online kit. It list unloaded backlash at (< 1 deg.). All the other gear box sheets are around 25 arc as you stated. This sheet didn't look correct when comparing it to the others, so I went online to download the sheet and it states (1.6 deg.). So I was unsure how much play was to be expected. I did some tinkering after I posted the video. I slid the motor half way out and held the arm still and when moving the motor I could feel some play in the keyway. I cut a piece of .002 shim into a sliver the height of the exposed key and bent it to shape around the 3 sides of the keyway with some needle nose pliers. It was a tight fit getting the motor back in but I managed. After doing this the endplay was cut down to half of what it was in the video. Great design BTW, I'm learning a lot going through the kinematics in the software. I've been doing instrumentation and controls for the last 20+ years and just decided to get into robotics for the learning experience.
@michael-bigos Great thank you for the feedback. I will look into the keyway dimensions and see what can be done without making it too hard to assemble.
