230-007B

Check PLC positioning status

Access MOD function and check PLC status display for active M118/M119 positioning operations on the affected channel axes.

Look for axes showing 'PLC POS' status that should have returned to 'NC' control

Examine PLC program logic

Review PLC program for proper M118/M119 handshake completion and ensure positioning operations have proper abort conditions for NC stop requests.

Modifying PLC logic requires machine builder documentation and proper backup procedures

Force PLC positioning reset

Use PLC diagnostics to manually reset stuck positioning operations or cycle machine power to clear PLC positioning states.

Check machine parameter MP7500.x (PLC positioning timeout) if timeouts occur frequently

Verify PLC interface signals

Check PLC input/output status for axis handshake signals (typically W1030.x series) to ensure proper communication between NC and PLC systems.

Use TNCdiag or service software to monitor real-time PLC interface status

Check machine parameters

Verify MP1020 (PLC interface configuration) and related axis assignment parameters are correctly configured for the affected channel.

Incorrect PLC interface parameters can cause permanent axis control issues

Test axis control handover

Perform controlled test of axis assignment using M118/M119 commands to verify proper handshake functionality between NC and PLC.

Monitor W1030.x signals during handover test to identify exact point of failure

Check PLC cycle time

Monitor PLC diagnostics for cycle time and check if it exceeds normal operating range (typically should be under 10ms for most applications).

Access PLC diagnostics through MOD function to view real-time cycle time statistics

Analyze PLC program load

Review PLC program for inefficient loops, excessive calculations, or blocking operations that could delay axis handshake processing.

PLC program modifications should only be performed by qualified personnel with proper backups

Verify PLC hardware status

Check PLC module status LEDs and diagnostic information for hardware faults that could cause processing delays or communication issues.

Look for intermittent hardware faults that may not trigger separate PLC error messages

Check servo drive status

Access servo diagnostics through TNC service menus to verify all drives on affected channel are communicating properly and showing ready status.

Use Test Run menu to check individual axis response and communication status

Verify drive parameters

Check servo drive parameters related to PLC positioning mode and handshake timing, particularly parameters controlling mode switching delays.

Incorrect servo parameters can cause permanent positioning errors or axis runaway

Test axis communication

Perform axis reference run and manual movement tests to verify servo communication integrity and proper response to control commands.

Monitor drive status words during axis control handover to identify specific communication failures