Fanuc spindle alarm C4 means an invalid learning cycle is set for learning control in time synchronization mode — a setup alarm on machines using spindle learning control (piston-turning, cam grinding and similar repetitive-profile applications). The learning function needs a valid cycle definition and it did not get one.
Fanuc's two checks
- The velocity command: is the commanded speed appropriate for the learning cycle? An S-command inconsistent with the configured cycle produces an invalid combination — review the program's speed against the application's design values.
- Parameter 4425 (learning cycle): must be within 20 to 4800. Verify the value — out-of-range settings usually arrive via parameter restores or manual edits (the standing forensic rule: settings don't change themselves; see our AL-34 guide for safe correction practice).
Tip: C4/C5/C7 are all learning-control configuration alarms — nothing is broken; the setup is inconsistent. They appear at commissioning, after restores, or when a new part program pushes speeds outside the learned envelope. Correct against the application's documented values — learning-control setups are machine- and job-specific.
Related guides
- Fanuc spindle alarm C5 (compensation element invalid)
- Fanuc spindle alarm C7 (angle synchronization cycle)
- Fanuc αi drive alarms index
Learning-control setup trouble? JJ Automation commissions and corrects spindle learning-control configurations on site in NCR. WhatsApp us or call +91 88022 12394.