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FANUC Controller
Servo/Axis · Intermediate · 30-60 minutes
Fanuc Alarm 423 - SERVO ALARM: n AXIS CUMULATIVE TRAVEL EXCEEDED IN TORQUE CONTROL
Alarm 423 occurs during PMC axis control torque mode when the cumulative travel distance of the specified axis exceeds the allowable limit set in parameters. This is a protective function to prevent excessive axis movement during force/torque control operations, commonly used in pressing, grinding, or contouring applications.
423
Fanuc Alarm 423 - SERVO ALARM: n AXIS CUMULATIVE TRAVEL EXCEEDED IN TORQUE CONTROL
SERVO ALARM: n AXIS EXCESS ERROR AT READY OFF
Position deviation exceeded the allowable limit while the servo was in the Ready-Off state (servo drive not enabled). The axis drifted or was moved while servo power was not applied.
Root Cause Summary
Alarm 423 occurs during PMC axis control torque mode when the cumulative travel distance of the specified axis exceeds the allowable limit set in parameters. This is a protective function to prevent excessive axis movement during force/torque control operations, commonly used in pressing, grinding, or contouring applications.
Safety
- Position lost
- ⚠️ CRITICAL: Axis position data lost - rehome axis before operation
- Disconnect power to the machine before working on any electrical components. Lockout/Tagout procedures should be followed.
- Be careful when working around moving parts. Ensure the axis is properly supported before disconnecting any components.
- Electrostatic discharge (ESD) can damage sensitive electronic components. Use proper ESD precautions when handling encoders and servo drives.
- Refer to the machine's documentation for specific safety information and procedures.
- Position may be lost, do not operate the machine until the issue is resolved.
- Always wear appropriate personal protective equipment (PPE) and ensure the area is safe before troubleshooting.
Causes and Fixes
- 1
Navigate to SYSTEM > PARAM and check parameter 8245 for the faulted axis. This parameter sets the allowable cumulative travel distance in torque control mode (units in detection units).
- 2
Review PMC ladder logic and verify the torque control command duration and expected travel distance. Check PMC address G0140-G0143 (torque control command) for proper sequencing.
- 3
Increase parameter 8245 value if the process requires greater travel distance, or modify the PMC logic to reset torque control mode before exceeding the limit. Typical values range from 1000 to 50000 depending on application.
Increasing this parameter may reduce protection against runaway conditions in torque control mode
- 4
Reset alarm and verify PMC axis control operation. Monitor DIAGNOSIS > PMC AXIS to observe real-time cumulative travel distance during torque control operation.
Call a technician if:
- ·Encoder replacement required
- ·Servo amplifier replacement needed
- ·Parameter restoration from backup required
Prevention
- Regular encoder cable inspection
- Proper cable strain relief installation
- Maintain parameter backup files
- Monitor servo diagnostic screens during PM
Common Mistakes
- Powering up with encoder disconnected
- Incorrect encoder parameter settings
- Poor cable routing near interference sources
- Inadequate cable strain relief
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