Shoulder Joint Backlash 2.5X over Spec – AR4 MK3
I’m seeing excessive backlash in the shoulder joint of my new AR4-MK3.
Motor/gearbox: 23HS22-2804D-YGS50-AR4, 50:1 planetary.
Spec lists backlash ≤15 arc-min (~0.25°).
Measured backlash at the shoulder joint is ~0.6° total on direction reversal. All external fasteners, hubs, and couplers, internal threads are tight, and the backlash remains with load removed, so it appears internal to the gearbox.
Is this amount normal in practice? Are these gearboxes serviceable (preload, shims, bearings), or is replacement the only option? Any known wear or failure modes?
Is there a disassembly document on the Gear-Box to review internal components?
Thanks, Mech
Hello, there was a recent batch of gearboxes that had .6 to .8 backlash. I had a couple of them myself. If you contact the Stepperonline customer service team via cs09@omc-stepperonline.com they will help you with the details in sending you a replacement gearbox.
Appreciate it. Unfortunately, this wire harness is too integrated for us to swap the motor out at some later point. Unless we can figure out how to take the gearbox off, but it seems like there’s a trick that isn’t supposed to be obvious.
Regarding the planetary gearbox removal, it's a good idea to reach out to StepperOnline's technical support directly before attempting anything. They would know the exact design and whether the gearbox can be safely separated without damaging the motor's windings or encoder (if equipped). Improper disassembly could affect alignment, torque, or even void any warranty for future use. Please let me know what they advise!
hi, same issue with backlash, i ordered the robot at january. R3D from Poland if you remember Chris Annin Can you tell me guys how to mesure it to show for OMC?
I had sent them a video showing the arm movement as well as a couple picks with a digital angle gauge showing the degrees or movement.