28004

Check E-STOP Button Status

Verify all emergency stop buttons are released and not mechanically stuck. Check HMI diagnostics screen under Service > Diagnostics > Safety for E-STOP status.

Never bypass emergency stop circuits for testing purposes

Verify Safety Relay Chain

Access PLC diagnostics via HMI Service menu and check safety relay inputs. Monitor DB31 safety interface signals for proper 24V levels.

Use oscilloscope to check for intermittent safety signal dropouts

Test Safety Circuit Continuity

With system powered down, measure continuity through complete E-STOP chain including all series-connected safety contacts and monitoring relays.

Reset Safety System

After verifying all E-STOP buttons are released, perform safety system reset via HMI Machine > Reset or use NC/PLC Reset function key.

Inspect All Safety Guards

Physically check all machine guards, doors, and covers are properly closed and latched. Verify safety switch actuators are properly aligned.

Do not attempt to override safety interlocks - this violates safety regulations

Check Safety Input Status

Navigate to HMI Diagnostics > PLC > Inputs and monitor safety door input signals (typically DB31.DBX addresses). Verify 24V signal presence when doors are closed.

Test Light Curtain Function

If equipped with light curtains, check beam alignment and clean optical surfaces. Verify muting functions are not active inappropriately.

Light curtain diagnostics often available via separate display unit - check for beam interruption history

Validate Interlock Wiring

Check wiring connections at safety switch terminals and verify proper voltage levels. Look for loose connections or damaged cables.

Check Drive Safety Status

Access drive diagnostics via HMI Service > Drive > Safety Status. Check for active STO (Safe Torque Off) or other safety function alarms in SINAMICS.

Use STARTER software for detailed drive safety diagnostics if HMI access is limited

Verify Safety Communication

Check PROFISAFE communication status between SINUMERIK and drives. Monitor cyclic data exchange and F-parameters in safety configuration.

Inspect Drive Hardware

Check drive status LEDs and verify proper 24V supply to safety circuits. Ensure STO terminals have correct voltage levels when safety system is active.

Reset Drive Safety Functions

After clearing fault cause, reset drive safety functions via HMI Machine > Drive Reset or through SINAMICS safety acknowledge procedure.

Check Safety PLC Status

Navigate to HMI Service > PLC > Safety PLC Status. Look for safety program faults, watchdog errors, or F-CPU diagnostic messages.

Review Safety Program Logic

Use STEP 7 Safety or TIA Portal Safety to check F-program for logic errors. Verify safety function blocks are executing properly.

Check safety program cycle time - excessive cycle time can trigger watchdog faults

Verify Safety Hardware

Check F-CPU module status LEDs and ensure proper seating in rack. Verify safety I/O modules are functioning and properly configured.

Perform Safety System Restart

Execute complete safety system restart sequence including F-CPU restart and safety program reload if necessary.

Identify External Safety Devices

Review machine documentation to identify all external safety systems connected to SINUMERIK safety inputs. Check each device status individually.

Check External Device Status

Verify status of external safety PLCs, laser scanners, or other safety devices. Check their individual diagnostic displays or status indicators.

Verify Safety Signal Wiring

Check wiring from external safety devices to SINUMERIK safety inputs. Verify proper 24V signal levels and check for wiring faults.

Reset External Safety Systems

Follow manufacturer procedures to reset external safety devices, then reset SINUMERIK safety system after all external faults are cleared.