OT0511

Navigate to POSITION screen and verify C-axis absolute position. Note the current machine coordinate position value.

Access SYSTEM > PARAM and check parameter 1320 (stored stroke limit), parameter 1326 (negative side travel limit for C-axis). Verify if current position exceeds the negative limit value set in P1326.

If limits are correct, clear alarm, then jog C-axis in positive direction using manual handle mode (parameters P1401 bit 0 must allow overtravel release). Use OVER TRAVEL RELEASE + direction button if available on panel.

Do not force movement if mechanical obstruction exists. Verify no physical interference before jogging.

If software limits are incorrect, adjust parameter 1326 to proper negative limit value. Set parameter 1320 bit 4 (OTL) = 1 to enable software overtravel checking. Cycle power and re-establish reference point.

Navigate to SYSTEM > DIAGNOSIS screen. Check diagnostic number 300 + C-axis number (typically D304 for 4th axis C-axis) to view limit switch status. Bit pattern will show –OT switch active.

Physically inspect C-axis negative limit switch and dog/cam position. Verify switch is not damaged, wiring is intact, and dog has actuated the switch properly. Check for mechanical binding or collision.

Ensure machine is in E-STOP before physical inspection of limit switches.

If switch is functioning correctly, press OT RELEASE button + manual jog in positive direction to retract axis from limit. Monitor diagnostic D304 to confirm –OT signal clears as axis moves away.

If limit switch is faulty or misadjusted, adjust dog position or replace defective switch. After repair, verify diagnostic D304 shows correct switch status, then establish reference point using parameter 1815 (reference position).

Check alarm history (ALARM > HISTORY) for related alarms: SV0441 (absolute position lost), SV0410 (overload), or servo alarms 400-series. Navigate to SYSTEM > DIAGNOSIS and check D400-D407 for C-axis servo status.

Verify encoder battery voltage on amplifier. Check parameter 1815 (reference point return position for C-axis). Navigate to ABSOLUTE > CHECK screen to verify absolute encoder data is valid.

If position data is corrupted, perform manual reference point return after clearing alarm. Set parameter 1815 to known zero position value. Execute G28 H0 (reference point return) for C-axis to re-establish position.

Ensure C-axis is physically at a safe position before executing reference point return to avoid collision.

If encoder failure is confirmed, replace encoder battery or encoder unit. After replacement, execute absolute position re-setting procedure per Fanuc manual. Set parameters 1815 (reference point) and re-verify travel limits in P1320/P1326.