27023

Access Diagnostics → Alarms in SINUMERIK HMI. Verify if alarm 27010 (Tolerance exceeded) appears before 27023. Note the axis number (%1) and timestamp correlation with NC program execution.

Check MD33020 and MD33021 (Stop B ramp times in ms) via NCK Parameters menu. Compare against machine mechanical specifications and axis load. If values exceed 500ms for standard servo axes, reduce incrementally by 10-15% and test with G04 P2 dwell statements.

Do not reduce below 100ms without consulting machine builder; risk of servo saturation.

Verify MD33025 STOP_B_TOLERANCE (permissible velocity threshold in mm/min or deg/min). If set below 10mm/min for linear axes, increase to 15-20mm/min to account for axis settling time.

Load and execute a test program with isolated axis jog commands: G01 X50 F500; M00 STOP F; followed by manual trigger of Stop B via safety circuit. Monitor real-time axis velocity in Diagnostics → Actual Values. Confirm deceleration profile matches MD ramp settings.

In Siemens HMI, navigate to Diagnostics → Inputs/Outputs. Monitor the safety input signal corresponding to Stop B (cross-reference machine documentation or PLC symbol table for signal name, typically STOP_B_TRIGGER or equivalent).

Check MD SAFETY_PLC_INPUTS parameter block. Verify the Stop B input is mapped to the correct safety digital input channel (e.g., DI 4.0, DI 4.1). Confirm input debounce time in MD33030 (STOP_B_DEBOUNCE) is set to 20-50ms.

In PLC program (via STEP7 or equivalent), inspect the safety logic that triggers Stop B. Use Logic Analyzer to capture input signal timing relative to axis position and velocity commands. Verify the stop command is asserted for at least 2 full NCK cycles (typically 8-12ms).

Do not modify safety PLC code without formal safety validation documentation.

If signal timing is correct, test the physical safety circuit (e-stop button, safety relay modules) with a multimeter. Confirm contact closure voltage and resistance per IEC 61508. Replace any safety relay module showing contact chatter or delayed response.

Access the servo drive diagnostics (SIMODRIVE via STARTER software or native drive display). Check Drive Status → Fault History for communication errors, parameter set mismatches, or velocity loop warnings. Note any CRC errors or cycle time overruns.

Verify PROFIBUS (if used) signal quality: In NCK Parameters → Communication → PROFIBUS, check token rotation time and diagnostic counters. Target cycle time should be ≤12ms. If cycle time exceeds 20ms, reduce baud rate diagnostic load or check for cable EMI issues.