231-8850

Enter PLC programming mode

Press MOD key, select 'PLC', then 'Program Test' to access PLC monitoring functions. Identify the output marker controlling drive enable for the affected axis (typically outputs like O10-O19 for axis enables).

Only modify PLC logic if you have proper authorization and backup of existing program.

Monitor drive enable output timing

Use PLC Test Functions to observe the drive enable output during the operation sequence. Watch for the enable signal state when the alarm occurs - it should transition to FALSE/0 but may be stuck TRUE/1.

Use the PLC Status display to capture the exact moment the alarm triggers - press and hold markers to freeze the display for analysis.

Review PLC enable logic conditions

Examine the PLC program rung controlling the drive enable output. Look for interlocks or conditions that may prevent the enable from being removed during mode changes, shutdown, or configuration operations.

Common culprits include missing reset conditions for latch instructions or improper use of set/reset coils without corresponding transition logic.

Correct PLC logic timing

Modify the PLC program to ensure drive enable signals are removed appropriately during control state changes. Add conditions monitoring system markers like M_SysStopCond or M_AxisDisableReq if available on your TNC generation.

Test modified PLC logic thoroughly in single-step mode before normal operation.

Check axis servo status

Access MOD > System Information > Axis Status and examine the affected axis (%1). Look for 'Servo Active' or 'Position Control Active' indicators that should be OFF for the intended operation.

On iTNC 530/TNC 620/640, you can also check Service > Diagnosis > Drive Diagnosis for detailed real-time drive state information.

Cancel active positioning tasks

Press the NC STOP button to terminate any running NC programs. Clear any active MDI commands. Ensure manual mode is inactive and no traversing is pending.

Ensure machine is in safe position before canceling motion commands.

Disable axis manually if required

If performing diagnostic or setup operations, use MOD > Axis Enable/Disable function to explicitly command the affected axis to disabled state before proceeding with the configuration change.

Some maintenance functions like 'Test Run' or parameter modifications automatically require disabled drives - attempting these with active drives triggers this alarm.

Review operation sequence documentation

Consult the specific function documentation (User's Manual or Service Manual for your TNC model) to verify the correct pre-conditions required, including drive state, for the operation you're attempting.

Functions like axis compensation table modification, encoder reference procedures, or some MOD functions explicitly require drives to be inactive first.

Verify safety circuit status

Check the PLC status display (MOD > PLC > Status) for safety-related input markers. Look for E-Stop inputs (typically I0-I3), enabling switch inputs, and safety PLC communication status markers.

Never bypass safety circuits. Ensure all safety devices are functioning properly.

Complete E-Stop reset sequence

If E-Stop was activated, ensure full reset: 1) Release E-Stop button, 2) Verify safety circuit closed indicator on control, 3) Press acknowledgment button if required, 4) Re-enable drives through proper sequence (typically enabling switch + START).

On machines with safety PLC integration, check for pending safety acknowledgments in the safety system diagnostics - incomplete handshake can leave drives in limbo state.

Check machine parameter safety configuration

Access MOD > Machine Parameters > CfgSafetyPLC (or CfgEmergencyStop depending on TNC generation). Verify parameters for drive disable behavior during safety events are correctly configured.

Parameter like 'driveDisableDelay' or 'safetyReactionTime' affect how quickly drives respond to safety signals - improper values can cause state timing issues.