TL;DR
Position deviation alarms indicate the robot arm is not reaching the commanded position. Check for mechanical interference, verify the zero position mastering, and inspect the speed reducer before calling FANUC service.
What you might see
- FANUC position deviation alarm during motion
- robot arm drifts from the taught point over time
- mastering alarm after an E-stop or collision
- joint noise on one axis during move
Likely causes
Zero mastering data lost after a collision or battery failure
Speed reducer backlash increasing from wear
Mechanical interference preventing the arm from reaching the commanded position
Servo drive tuning parameter drift causing following error
Required tools
- FANUC Teach Pendant (mastering procedure access)
- Multimeter for battery voltage check (mastering battery)
- LOTO kit
Safety first
- Never enter the robot working envelope during any robot motion or mastering procedure. Robotic arms cause fatal crush injuries.
- Mastering procedures require the robot to move to specific positions. Ensure the area is clear and all personnel are outside the safety fence before starting.
Procedure
- 1
Check for a mastering alarm on the Teach Pendant. If mastering data has been lost, perform the FANUC zero position mastering procedure for the affected joint.[1]
- 2
Inspect the full robot travel path for any tooling, fixturing, or foreign object interference that could block the robot from reaching the commanded point.
Warning: Keep all personnel outside the robot working envelope before running any diagnostic motion, even at low speed. FANUC robots move unexpectedly when mastering procedures are active. - 3
Check the servo drive following error for the affected joint in the FANUC diagnostic screen. A steadily increasing following error points to mechanical drag or reducer wear.[1]
- 4
Lock out the robot and manually move the affected joint back and forth through its range. Feel for any tightness, intermittent binding, or unusual resistance.
- 5
Listen for grinding or clicking from the speed reducer during slow manual motion. Grinding from the speed reducer indicates internal damage.
- 6
If mastering and mechanical checks do not resolve the alarm, contact FANUC service. Speed reducer replacement requires FANUC tooling and procedures.
Sources
FANUC FANUC R-2000iC / R-1000iA Body-in-White Spot Welding Robot Cell general technical documentation, FANUC
FANUC R-2000iC / R-1000iA robot operator manual, position deviation diagnosis and mastering procedures (general)
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