What causes FANUC alarm 950?

Tool change mechanism jammed or obstructed by a chip, tool, or mechanical issue. ATC or turret proximity switch not actuating during the change sequence. Air or hydraulic pressure insufficient for the ATC actuator. Tool not properly seated in the spindle or pocket preventing transfer. Tool change sequence timeout — mechanism too slow to complete in the allotted time.

How do I fix FANUC alarm 950?

1. Check the ATC or turret area for mechanical obstruction, chip buildup, or tools out of position. 2. Run a manual ATC cycle from the Fanuc maintenance screen to identify where the sequence stops. 3. Check the ATC proximity switches and sensors for correct actuation. 4. Verify air or hydraulic pressure is within specification for the ATC. 5. Inspect tool holder taper and retention mechanism for damage or contamination.

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FANUC Controller

System · Advanced · 30 minutes - 4 hours

Alarm 950

Fanuc Alarm 950 - PMC Watchdog Timeout

Alarm 950 indicates a critical PMC system malfunction preventing proper execution of the ladder program. This alarm is triggered by PMC hardware failures, corrupted ladder logic, PMC memory errors, or communication failures between the CNC and PMC subsystem. Immediate diagnosis of PMC status and ladder execution is required.

FANUCSystemAdvanced30 minutes - 4 hours

950

Fanuc Alarm 950 - PMC Watchdog Timeout

PMC Watchdog

Root Cause Summary

Alarm 950 indicates a critical PMC system malfunction preventing proper execution of the ladder program. This alarm is triggered by PMC hardware failures, corrupted ladder logic, PMC memory errors, or communication failures between the CNC and PMC subsystem. Immediate diagnosis of PMC status and ladder execution is required.

Safety

PMC controls safety functions

Causes and Fixes

1
Navigate to PMC > PMCPRM > STATUS screen and check PMC alarm code displayed. Note any specific error numbers (e.g., WN52, WN53, ER15) which indicate ladder syntax or memory allocation errors.
2
Access PMC > LADDER > MONITOR to verify ladder execution. If ladder is not running or frozen, check for loop errors or scan time overruns indicated in SYSTEM > PMC > LADDER SCAN TIME display.
3
Reload the PMC ladder program from verified backup using FANUC Ladder-III software or from CF/USB card. After reload, perform PMC > PMCPRG > WRITE operation and cycle power.
Ensure machine is in safe state before power cycle. Document all PMC parameters and ladder version before reloading.
4
If alarm persists after reload, check PMC parameters (K-parameters, D-parameters, C-parameters) in PMCPRM menu for out-of-range values or corruption. Reset to machine builder default values if necessary.

Service Recommendedmedium confidence

Call a technician if:

·PMC card hardware failure confirmed
·Ladder program corruption cannot be resolved
·Multiple PMC system components affected

Prevention

Regular PMC program backups
Monitor PMC memory usage trends
Maintain clean electrical connections
Implement UPS protection for power quality

Common Mistakes

Attempting ladder edits without proper training
Ignoring PMC memory usage warnings
Failing to backup before PMC operations
Mixing incompatible PMC program versions

Related Alarms

949 951 952 900

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