330-00CB

Visual inspection of all guard doors

Check all guard doors around the machine for proper closure. Look for doors that appear closed but may not be fully engaged with their safety switches.

Ensure machine is in EMERGENCY STOP before inspecting guard doors

Check door alignment and latching mechanism

Verify that door hinges are not sagging and that the door properly aligns with the safety switch actuator. Check for worn door seals or mechanical interference.

Look for wear marks on the door frame that indicate misalignment over time

Test door closure with gentle pressure

Apply gentle inward pressure on each door while observing the safety switch engagement. The switch should activate with a distinct click or visual indicator.

Do not force doors closed as this may damage safety switches

Clear alarm and test

After ensuring all doors are properly closed, clear the alarm using the TNC control and attempt to restart the safety self-test sequence.

Access safety input diagnostics

Navigate to MOD function → Diagnosis → Safety inputs to view the real-time status of all safety door inputs for the affected axis group.

Document which specific safety inputs show 'OPEN' status for troubleshooting

Test individual door switches

With doors closed, manually actuate each safety switch while monitoring the diagnostic display. Switches should change state immediately when actuated.

Only qualified personnel should access safety switch wiring and connections

Measure switch continuity

Using a multimeter, check continuity across the safety switch contacts in both open and closed positions. Replace switches that show intermittent or no continuity.

Disconnect power and follow LOTO procedures before electrical testing

Verify switch mounting and actuator alignment

Check that safety switches are securely mounted and that door actuators properly engage the switch mechanism through its full travel range.

Inspect safety circuit wiring

Visually inspect all wiring from safety switches to the safety relay module and TNC safety inputs. Look for damaged insulation, loose connections, or corrosion.

Ensure machine power is OFF and follow electrical safety procedures

Check safety relay module status

Examine the safety relay module LED indicators to determine if the fault is at the relay level or upstream at the TNC safety input processing.

Consult the safety relay module manual for specific LED diagnostic codes

Measure circuit continuity end-to-end

Using a multimeter, verify continuity from each safety switch through the complete circuit path to the TNC safety input terminals.

Test both normally open and normally closed contacts if using dual-channel safety switches

Check for electromagnetic interference

Verify that safety circuit wiring is properly shielded and routed away from high-power motor cables that could induce interference.

Access safety parameter settings

Navigate to MOD function → Machine parameters → Safety parameters to review the door monitoring configuration for the affected axis group.

Only authorized personnel should modify safety parameters

Verify axis group door assignments

Check that the correct safety door inputs are assigned to the specific axis group mentioned in the alarm. Verify parameter assignments match the physical door layout.

Compare current parameters with machine documentation or backup parameter files

Review safety logic configuration

Confirm that door monitoring logic (normally open/closed) matches the actual safety switch wiring configuration for each door input.

Incorrect safety logic configuration can compromise machine safety

Perform safety system validation

After any parameter changes, perform a complete safety system validation test to ensure all door monitoring functions operate correctly.

Check TNC safety system diagnostics

Access the TNC internal safety diagnostics to check for hardware faults in the safety input processing circuits or safety CPU modules.

Look for any additional safety-related alarms that may indicate hardware issues

Perform safety system self-test

Initiate a manual safety system self-test from the TNC diagnostics menu to verify proper operation of all safety monitoring circuits.

Safety self-tests should only be performed by qualified technicians

Contact Heidenhain technical support

If hardware fault is suspected, document all diagnostic information and contact Heidenhain technical support for advanced troubleshooting guidance.

Have TNC software version, machine serial number, and complete alarm history ready