Fanuc spindle alarm C9 means that in spindle synchronization, the position error exceeded the alarm detection level (parameter 4516) — the angular alignment between the synchronized spindles drifted beyond tolerance. Where C8 watches speed tracking, C9 watches position tracking — the alignment that matters when a chuck must grab a shaped part at the correct orientation. Fanuc routes the troubleshooting to the C8 procedure, because the causes are the same:
The C8 checklist, applied to position error
- Sequence: motor excitation (SFR/SRV) cycled while synchronization is active → accumulated position error and a violent catch-up. Fix the ladder: excitation off only after synchronization is released.
- Overload during cutting: the follower loses ground under the cut — review conditions and tooling.
- Detection level: only with the above excluded, review parameter 4516 against the builder's documented value — never simply raised until quiet; a loose position tolerance on a synchronized hand-off is how shaped parts get grabbed mis-oriented.
Tip: C8 and C9 usually travel together — whichever limit is tighter trips first. Diagnose them as one synchronization-quality problem: sequence timing, then load, then the mechanical health of both spindles (compare load meters), and the detection levels last.
Related guides
- Fanuc spindle alarm C8 (speed deviation) — the full procedure
- Fanuc spindle alarm 36 (error counter overflow)
- Fanuc αi drive alarms index
C9 mis-aligning your part transfers? JJ Automation diagnoses spindle synchronization end to end — sequence, mechanics, parameters — on site in NCR. WhatsApp us or call +91 88022 12394.