What causes Siemens SINUMERIK alarm 28031?

Parameter or machine data configuration error. Hardware fault on the NC or drive component. Part program error or illegal command. Communication fault between NC and drive or I/O modules. Software or firmware error requiring system restart.

How do I fix Siemens SINUMERIK alarm 28031?

1. Note the complete alarm text including any axis, channel, or block number values. 2. Check for related alarms active simultaneously in the SINUMERIK alarm list. 3. Power cycle the machine to clear transient faults. 4. Review the SINUMERIK machine data for parameters related to the alarm. 5. Consult the Siemens SINUMERIK alarm manual for alarm 28031 detailed remedy.

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Siemens SINUMERIK Controller

Servo/Axis · Intermediate · 30-120 minutes

Alarm 28031

Siemens 840D 28031 - Serious alarm on NCU not yet acknowledged, axes still in follow-up

Alarm 28031 indicates that a serious alarm (class 2 or higher) has been triggered on a secondary NCU in a multi-NCU system but has not been acknowledged by the operator. The primary NCU detects this unacknowledged serious alarm and places all axes in follow-up mode (Folgeregelung) rather than allowing independent motion, creating a safety interlock condition. This is a system-level synchronization issue specific to distributed SINUMERIK 840D configurations.

Siemens SINUMERIKServo/AxisIntermediate30-120 minutes

28031

Siemens 840D 28031 - Serious alarm on NCU not yet acknowledged, axes still in follow-up

Serious alarm on NCU not yet acknowledged, axes still in follow-up

Root Cause Summary

Alarm 28031 indicates that a serious alarm (class 2 or higher) has been triggered on a secondary NCU in a multi-NCU system but has not been acknowledged by the operator. The primary NCU detects this unacknowledged serious alarm and places all axes in follow-up mode (Folgeregelung) rather than allowing independent motion, creating a safety interlock condition. This is a system-level synchronization issue specific to distributed SINUMERIK 840D configurations.

Safety

Refer to Siemens documentation
Ensure qualified technician performs repairs

Causes and Fixes

1
Access the secondary NCU (%1) HMI interface via Siemens KTP or HMI terminal. Navigate to Alarms/Diagnostics menu and identify the active serious alarm code.
Do not attempt to move axes while follow-up mode is active; verify secondary NCU is accessible and responsive.
2
Review the secondary NCU alarm log in NCK > Alarms > Active to confirm alarm type and time of occurrence. Cross-reference the alarm code in SINUMERIK 840D documentation.
3
Acknowledge the serious alarm on the secondary NCU using the HMI Acknowledge function (typically a dedicated soft key or Ctrl+A sequence) or via PLC input signal (I 20.0 - Alarm Acknowledge, verify with machine builder documentation).
4
Verify alarm 28031 clears from the primary NCU and that follow-up mode is disabled. Check MD 30300 = 0 (Follow-up control disabled). Resume normal axis operation.

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