PMC System Alarm
Fanuc · Series 20 CNC
What does 950 mean?
This alarm indicates a general system error within the Programmable Machine Controller (PMC) of the Fanuc Series 20 CNC. The PMC handles the machine's ladder logic, I/O, and interlock functions, so an error here means basic machine operations, axis movement, or tool changes may be impossible.
Common Causes
- Error in the PMC ladder program (e.g., syntax error, invalid logic).
- Faulty PMC hardware or memory module.
- Loss of PMC parameters or user data due to battery failure.
- I/O module malfunction or communication error with I/O devices.
- Excessive noise on the I/O lines affecting PMC operation.
Repair Steps & Checklist
Click steps to track your progress.
- 1
Check the PMC diagnostic screen for any specific sub-alarms or error messages related to the PMC.
- 2
Verify the PMC ladder program for recent changes or known issues. If a backup is available, try reloading a known good program.
- 3
Check the PMC battery (if separate from main CNC battery) and replace if low to prevent parameter loss.
- 4
Inspect all I/O modules and their wiring for loose connections, damage, or short circuits.
- 5
Power cycle the CNC system and PMC to clear any transient errors. If the alarm persists, the PMC module may be faulty.