1339

Common Causes

• Spindle or C-axis shaft rotated by hand, gravity, or residual cutting load while the servo was off with the door open
• Workpiece or chuck shifted during the door-open period, moving the spindle position
• External force (tool change contact, part loading, tailstock thrust) turned the spindle or M-tool spindle while unclamped
• C-axis/spindle position feedback drift or encoder slipping so the read position differs from the switch-off position

Troubleshooting Steps

1. 1Note whether the [Object] shown is SYSTEM (main spindle/C-axis) or M-TOOL SPINDLE, and whether the machine was in C-axis control, synchronized rotation, or flat turning when the door was opened.
2. 2Check for anything that could have turned the spindle while the door was open: manual rotation of the chuck, part loading/unloading force, or a heavy unbalanced chuck/fixture rotating by gravity. Secure the work and remove the load before closing the door.
3. 3Verify the C-axis or spindle brake/clamp is holding during the door-open servo-off state; if the shaft can be rocked by hand, inspect the clamp function and its air/hydraulic supply.
4. 4If the spindle did not physically move, check the spindle/C-axis position encoder coupling and feedback cable for slip or looseness that would make the read position differ from the switch-off position.
5. 5After correcting the cause, re-establish position (re-home or re-orient the C-axis/spindle as applicable) before resuming synchronized rotation or flat turning.
6. 6If the alarm returns with no visible shaft movement, record the alarm number and object and contact Okuma service.