What causes FANUC alarm 418?

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 418?

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

Parameter · Intermediate · 30-60 minutes

Alarm 418

Fanuc Alarm 418 - SERVO ALARM: n-TH AXIS PARAMETER SETTING ERROR

Alarm 418 indicates that one or more servo parameters for the specified axis contain invalid or out-of-range values that conflict with the servo amplifier configuration or axis setup. This typically occurs after parameter restoration, manual parameter editing, battery failure causing parameter corruption, or mismatched amplifier and motor combination requiring different parameter settings.

FANUCParameterIntermediate30-60 minutes

418

Fanuc Alarm 418 - SERVO ALARM: n-TH AXIS PARAMETER SETTING ERROR

SERVO ALARM: n-TH AXIS PARAMETER SETTING ERROR

Root Cause Summary

Alarm 418 indicates that one or more servo parameters for the specified axis contain invalid or out-of-range values that conflict with the servo amplifier configuration or axis setup. This typically occurs after parameter restoration, manual parameter editing, battery failure causing parameter corruption, or mismatched amplifier and motor combination requiring different parameter settings.

Causes and Fixes

1
Navigate to SYSTEM > PARAM and identify the affected axis number (n) from the alarm display. Note the axis number for parameter review.
2
Check servo parameter 1815 (motor serial number/type code) for the n-th axis. Verify it matches the actual motor installed. Cross-reference with motor nameplate data and amplifier compatibility charts in the servo motor specification manual.
Incorrect motor type setting can cause amplifier damage during operation
3
Verify gear ratio parameters 1820 (CMR), 1821 (DMR), 1822 (CAP), and 1823 (DAP) for valid non-zero values. Calculate actual gear ratio and confirm it matches mechanical setup. Check that encoder resolution in parameter 1824 matches actual encoder specification.
4
Review position loop gain (parameter 1825), velocity loop gains (parameters 1826-1827), and ensure values are within recommended ranges from servo tuning manual (typically 0-99999 for position gain). Compare against default parameters for your motor/amplifier model and reload if necessary.

DIY Feasiblehigh confidence

Call a technician if:

·Parameter backup/restore required
·Motor replacement needed
·Safety system modifications required

Prevention

Always backup parameters before modifications
Use FANUC Servo Guide for parameter calculation
Verify motor nameplate data before parameter entry
Document all parameter changes with timestamps

Common Mistakes

Copying parameters between different motor types
Setting gains too high for mechanical system
Ignoring motor inertia ratio calculations
Not validating parameter ranges before entry

Related Alarms

417 419 401 410

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