Troubleshooting workflows
Troubleshooting Repeatability Degradation Over Time
For maintenance and process engineers investigating why a robot's part-to-part repeatability has gradually worsened. Focus on alarm history, mastering integrity, and mechanical damage rather than invented metrology.
- Step 1.
Confirm the trend with data
Review process capability or vision inspection data over time to confirm a genuine gradual decline rather than a single step change.
- Step 2.
Rule out a single-event cause
Check for a collision, program change, or fixture modification that coincides with the start of the decline before assuming gradual change.
- Step 3.
Review the alarm history
Look through the alarm log for encoder and mastering-related alarms such as BZAL, BLAL, and SRVO-038 Pulse mismatch. Any of these can indicate lost or suspect mastering that shows up as degraded repeatability.
- Step 4.
Check encoder backup batteries
If BZAL or BLAL has appeared, replace the encoder backup batteries per the documented procedure and verify the alarm doesn't return. Lost encoder data means mastering can't be trusted.
- Step 5.
Verify mastering integrity
Confirm the robot's current mastering is valid. If mastering is suspect, restore SYSMAST.SV from a known-good backup or have a qualified technician remaster per the FANUC procedure.
- Step 6.
Inspect for mechanical damage
Have a qualified technician inspect the robot for signs of prior collision or mechanical damage on the arm, wrist, and mounting. Damage that wasn't logged as an alarm can still shift repeatability.
- Step 7.
Check end-of-arm tooling and fixture security
As general shop practice, verify the gripper, tool changer, locating pins, and fixture mounting are tight and undamaged. Loose tooling or fixtures produce part-to-part variation that looks like robot drift.
- Step 8.
Address the leading contributor
Base the corrective action on what the alarm history, mastering check, and inspection actually found. Don't compensate for an unknown cause with program offsets.
- Step 9.
Verify improvement with process data
After the corrective action, monitor process capability data to confirm repeatability has returned to an acceptable level.
Common questions
- How long does Troubleshooting Repeatability Degradation Over Time take?
- Troubleshooting Repeatability Degradation Over Time is rated Advanced and takes about 60 minutes across 9 steps.
- What tools do I need?
- You will need Teach pendant, Historical process capability data.
- What should I do before starting?
- Process data showing the trend of degrading repeatability over time.
- What is the first step?
- Confirm the trend with data. Review process capability or vision inspection data over time to confirm a genuine gradual decline rather than a single step change.