28032

In Siemens HMI (SINUMERIK Operate or custom panel), navigate to Diagnostics > NCU > Alarms and verify alarm 28032 is current and not historical.

Check PLC program logic: Monitor input variable corresponding to NCK e-stop request (typically in the cyclical PLC interrupt OB1 or dedicated SIMATIC safety function). Verify the e-stop input is being incorrectly held TRUE by examining the PLC source code or debug view.

Do not override e-stop without understanding root cause of PLC signal assertion.

Verify Machine Data MD36100 (Enable external e-stop from PLC) and MD36110 (E-stop reaction) via Diagnostics > Machine Data > Servo. If MD36100 = 0, external PLC e-stop is disabled and this cause is unlikely.

If PLC signal is confirmed stuck, perform a PLC warm start (PLC stop/start cycle) via Program Manager to clear any latch conditions holding the e-stop assertion.

Navigate to Diagnostics > NCU > Network or Diagnostics > PLC > Network to view NCU-to-NCU communication status. Look for timeout errors, CRC failures, or frame loss on the inter-NCU interface.

Check Machine Data MD36130 (Network e-stop timeout value in ms). If set too low (e.g., <200 ms), transient network jitter may falsely trigger e-stop. Compare against expected network cycle time (typically 8–32 ms for PROFINET).

Perform a full NCU restart (Power-On Reset via keyswitch or HMI Reset All NCUs command) to re-establish NCU network synchronization and clear the trailing mode state.

Power-On Reset will interrupt any active program execution.

If alarm recurs, check physical PROFINET cable connections, port LEDs on Managed Switch (if used), and run Siemens SINUMERIK Commissioning Tool (or equivalent) to validate network topology and latency.

At the machine control panel, verify that the physical emergency stop button is fully released (rotated counterclockwise if twist-release type) and that no other safety interlock (door, guard) is blocking e-stop release.

In TIA Portal, open the Safety PLC project and review the safety function logic (typically in a safety interrupt OB or safety function block). Verify the e-stop latch command (OSSD output set) has a valid reset path triggered by operator action or cyclic enable condition.

Check Machine Data MD36150 (E-stop release mode): If set to 0, e-stop must be manually reset via PLC command; if set to 1, e-stop auto-clears after timeout. Confirm setting matches machine safety concept.