We changed out motor for Axis 3 on a AM120i/RJ2, did a Single Axis Master for Axis 3. Once I was done, we ran through the part program we were running to ensure all positions were good for production. That is when we found that the Axis 3 was off. Brought the robot back to home and checked Axis 3 Zero, numerous times, and found it would either be off in the + or - direction. Checked the gear on the motor and it is secured and when the motor is mounted we cannot feel any back lash on the motor telling us that the gear assembly may be bad. Any other suggestions would be helpful.
Fanuc 120i Axis 3 not holding Zero
- nlyons
- Thread is marked as Resolved.
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In order to properly check backlash you will need to have the servos engaged and the brakes released.
Place the axis neutral to gravity and use an indicator to measure the backlash. I suspect the RV gear is worn out.
Unfortunately I don't have a mechanical repair manual for that unit so I cannot provide the backlash specs. -
I have a maintenance manual to replace the RV reducer. Looks like this may be a press fit, is that correct? If so, what is the best way to remove the old RV Reducer? As the manual just states to remove it but does not state the best practice of removal.
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The outer bolt circle holding the RV reducer to the casting of the robot may need re-torquing. I have seen crashes where the reducer shifts throwing the mastering off.
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Does your manual have a backlash specification in it?
I would check the backlash first before replacing the reducer.
The RV is not a press fit but it is tight. There should be 2 threaded holes to use to push/pull it out. -
My manual does not show the back lash measurements. We switched out the J3 Arm Assembly with a spare robot and still the same issue, so that ruled out the RV Reducer. We tried a different motor as well and still the Master Position will not hold consistent. I have Single Axis and Zero Master the robot numerous times and yet the zero will not hold. I am not getting any other errors for a pulse coder mismatch.
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I'm baffled. Are you sure there is no play in the axis?
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