What causes FANUC alarm 450?

Servo amplifier internal fault — check amplifier fault LED and DGN 200 sub-code. Axis encoder cable damaged or connector loose causing position feedback loss. Servo motor winding fault or bearing failure. FSSB communication fault between CNC and amplifier. Axis mechanical binding or collision causing overcurrent.

How do I fix FANUC alarm 450?

1. Check DGN 200 and 204 on the Fanuc diagnosis screen for the specific servo sub-alarm. 2. Check the servo amplifier for fault LEDs and displayed fault codes. 3. Inspect encoder cable and connectors for the affected axis. 4. Manually move the axis with servo off to check for mechanical binding. 5. Power cycle the machine completely to reset the servo system.

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FANUC Controller

Servo/Axis · Intermediate · 30-60 minutes

Alarm 450

Fanuc Alarm 450 - SERVO ALARM: n AXIS ILLEGAL TANDEM CONTROL

Alarm 450 indicates an illegal tandem control configuration on the specified axis. This occurs when tandem axis parameters are incorrectly set, mismatched between master and slave axes, or when hardware connections do not match the parameter configuration. The servo amplifier detects incompatible tandem control settings during initialization or operation.

FANUCServo/AxisIntermediate30-60 minutes

450

Fanuc Alarm 450 - SERVO ALARM: n AXIS ILLEGAL TANDEM CONTROL

SERVO ALARM: n AXIS ILLEGAL TANDEM CONTROL

Root Cause Summary

Alarm 450 indicates an illegal tandem control configuration on the specified axis. This occurs when tandem axis parameters are incorrectly set, mismatched between master and slave axes, or when hardware connections do not match the parameter configuration. The servo amplifier detects incompatible tandem control settings during initialization or operation.

Causes and Fixes

1
Navigate to SYSTEM > PARAM and check parameter 1801 (tandem control axis specification). Verify the master axis number and slave axis number are correctly defined. Master should have slave axis number set, slave should have master axis number set.
2
Check parameter 1802 (tandem control mode) for both master and slave axes. Values must match: 0=no tandem, 1=position control tandem, 2=torque distribution tandem. Ensure both axes have identical settings.
3
Verify parameter 1804 (tandem error detection level) is set appropriately on both axes. If set to 0, tandem error detection is disabled which may cause this alarm.
4
Power cycle the CNC after parameter corrections. Press RESET and verify alarm clears. Check DIAGNOSIS > SERVO > tandem status to confirm proper tandem link establishment.
Parameter write enable (parameter 0000 bit 0=1) must be active to modify parameters. Changes require CNC restart.

DIY Feasiblemedium confidence

Call a technician if:

·Software update required
·Hardware replacement needed
·Mechanical alignment issues
·Persistent alarm after parameter corrections

Prevention

Always backup parameters before making tandem control changes
Verify hardware compatibility before enabling tandem control
Perform regular encoder calibration on tandem axes
Document all tandem parameter settings for future reference

Common Mistakes

Setting tandem parameters without verifying hardware support
Mixing different servo amplifier models
Forgetting to power cycle after parameter changes
Not checking encoder resolution compatibility

Related Alarms

401 414 415 435

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