Fanuc alarm SV0480: n AXIS:ILLEGAL SAFETY MODE (MNT)
safety/dual-check alarm · Fanuc 30i/31i/32i-B
What it means
The monitor detected an inconsistent combination of safety inputs - specifically safety signal mode D (guard open although no guard open request was input) was entered, or the guard is open while the guard unlock signal *LGD has not been output for axis n's group. This catches door/guard switch wiring that disagrees with the commanded lock state.
Likely causes
- Miswired or faulty guard state signal (SGD)
- Door forced open without the guard open request sequence
- Safety relay or door switch failure causing mode inconsistency
Triage note: Immediate stop; also check SGD connection integrity before blaming the CNC.
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
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Guard/door monitoring switch assembly
unit · Check if others ruled out
Need the part urgently?
Send us alarm SV0480 with your machine details — typical RFQ turnaround is 24–48h.