Fanuc alarm 31
αi SPM · Fanuc αi SPM
What it means
Motor lock alarm - motor failed to rotate as commanded; stopped or turning very slowly.
Likely causes
- Sensor-setting parameters incorrect
- Motor phase sequence wrong
- Feedback cable A/B phase signals wrong or cable faulty
- Spindle-lock (brake) sequence engaged
- Power leads / switching MCC not closed (spindle/winding switchers)
- SPM faulty
Triage note: CNC: SP0031 / 9031. Second most-searched spindle fault after AL-12. Rotate motor manually - no speed reading on diagnosis screen = sensor/cable, not SPM.
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
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MZi/BZi spindle motor sensor + cable
Spindle Sensor Kit · Primary suspect
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Spindle motor feedback cable
Encoder Feedback Cable · Common cause
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A06B-6111-Hxxx
Spindle Amplifier Module αiSP · Check if others ruled out
Need the part urgently?
Send us alarm 31 with your machine details — typical RFQ turnaround is 24–48h.