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Review the NC program at the alarm line. Check for direct axis commands to the synchronized slave axis (commonly U, V, W or secondary channel axes). Verify program structure ensures G51.2 (synchronous control OFF) is executed before commanding the slave axis independently.

Navigate to SYSTEM > PARAM and check parameter 1260 (synchronous control axis specification). Verify which axes are defined as master/slave pairs. Note the slave axis designation.

Check parameter 1261 (synchronous control mode) to confirm the synchronization type (0=not used, 1=tandem control, 2=gantry control). Ensure program logic matches the configured mode.

Correct the program by removing direct slave axis commands during synchronized operation, or add G51.2 P0 (synchronous control OFF) before commanding slave axis, then G51.2 P1 (synchronous control ON) to re-engage synchronization when needed.

Disabling synchronous control on gantry systems can cause mechanical binding. Ensure both axes are positioned identically before re-engaging.

Access PMC LADDER > PMCDGN and monitor G signals (G0140-G0143 for axis control start, G0144-G0147 for axis selection). Check if PMC is commanding the synchronized slave axis during alarm occurrence.

Navigate to SYSTEM > PMC > SIGNAL and check F0050.0-F0050.7 (synchronous control mode status signals). Verify PMC ladder logic reads these signals and inhibits axis control commands to slave axes when synchronization is active.

Review PMC ladder logic for MOVN, MOVE, MOVOR instructions targeting the slave axis control interface addresses. Add interlock conditions using synchronous mode status bits to prevent command execution during synchronized operation.

PMC modifications require backup of existing ladder and careful testing. Incorrect interlocks may prevent normal machine operation.

Check parameter 1268 (PMC axis control synchronous mode prohibition). Set bit corresponding to slave axis to 1 to enable hardware prohibition of PMC commands during synchronous mode if software interlocks are insufficient.

Navigate to SYSTEM > CURRENT > MODAL and check current G-code modal state. Verify if G51.2 (synchronous control) is active. If active when it should not be, issue G51.2 P0 in MDI mode to cancel synchronization.

Check DIAGNOSIS > #1006 (synchronous control status diagnosis). Bit 0 indicates synchronous mode active, bits 1-7 show specific synchronization states. If diagnosis shows active state but program shows cancelled, execute emergency stop and reset sequence.

Emergency stop on gantry systems may cause position deviation between master and slave axes requiring re-synchronization procedure.

Review parameter 1262 (synchronous control cancel condition). Bit settings determine when synchronous mode auto-cancels (reset, emergency stop, etc.). Adjust bit 0=1 to cancel on reset, bit 1=1 to cancel on emergency stop if appropriate for application.

After reset, execute proper synchronization sequence: position both axes to known reference, execute G51.2 P1 (synchronous ON), verify DIAGNOSIS > #1006 bit 0=1, then proceed with synchronized operation. Establish this as standard startup procedure.