OT0507

Navigate to POSITION screen and check current A-axis machine coordinate position. Note the absolute position value to compare against parameter limits.

Access SYSTEM > PARAM and verify parameter 1321 (negative software limit for 4th axis/A-axis). Check that the current machine position has not exceeded this value. Also verify parameter 1320 (positive limit) for proper range definition.

Check parameter 1006#1 (OT1) bit to confirm software overtravel detection is enabled. If disabled inadvertently, software limits are not monitored. Verify parameter 1005#4 (ROT) is set correctly for rotary axis type.

Clear alarm by jogging A-axis in positive direction using manual handle or JOG mode after setting parameter 1815#7 (OTB) to 1 to enable overtravel release. Reset OTB to 0 after recovery, then re-establish reference point via G28 or return to zero.

Only jog in the opposite direction of the overtravel. Do not force movement in negative direction as this may cause mechanical damage.

Navigate to SYSTEM > DIAGNOSIS and check diagnostic number 300 + A-axis number (typically D304 for 4th axis). Bit #1 shows negative limit switch status (1=activated). Verify signal state matches physical switch position.

Physically inspect A-axis negative direction limit switch and dog/cam mechanism. Verify switch is not mechanically stuck, dog is properly positioned, and switch actuates/releases correctly. Check for loose mounting or misalignment.

Ensure machine power is locked out when inspecting limit switches near moving components.

Check limit switch wiring from switch to axis amplifier X6 connector (*L1, *L2 signals). Measure continuity and verify 24VDC signal level. Check for damaged cables, loose connectors, or short circuits. Review ladder diagram (PMC > LADDER) for limit switch input signals.

If limit switch is confirmed faulty, temporarily bypass for recovery by setting parameter 1815#7 (OTB)=1, jog axis to safe position in positive direction, then replace limit switch and restore normal parameter settings. Re-verify operation with diagnostic screen.

Bypassing limit switches removes critical safety protection. Only use temporarily for recovery with constant supervision.

Check SYSTEM > ALARM history for preceding alarms such as SV0401 (absolute encoder battery alarm) or SV0410 (encoder feedback error). Navigate to SYSTEM > DIAGNOSIS D700-D799 (servo diagnostics) to verify encoder signal quality and battery voltage status.

Inspect A-axis servo amplifier LED indicators. Check for encoder alarm codes (solid red or flashing patterns). Verify encoder cable connections at motor and amplifier, especially connectors on rotary axis slip ring if applicable. Check for cable shield grounding.

If absolute encoder battery voltage is low, replace encoder battery per manufacturer procedure. After replacement, perform absolute encoder reset by accessing SYSTEM > PMC > KEEP RELAY and setting proper reference point re-establishment sequence, or use G28 reference return.

Encoder battery replacement requires proper reference point re-establishment. Document current position before battery replacement if possible.

Verify mechanical integrity of A-axis rotary table clamping system. Check for worm gear backlash, table slippage, or mechanical obstruction causing position loss. Re-establish reference point via return to zero sequence and verify position repeatability through test rotation cycles.