What causes FANUC alarm 407?

Incorrect synchronization between master and slave axes during synchronous control. Excessive load or inertia on the slave axis causing it to lag behind the master axis. Mechanical issues such as binding, worn components, or improper lubrication in the slave axis drive train.

How do I fix FANUC alarm 407?

1. Check the program to ensure the synchronous control parameters are set correctly, such as the master and slave axis assignments, synchronization timing, and allowable position error. 2. Inspect the slave axis drive train for any mechanical issues that could be causing excessive load or inertia, such as worn bearings, gears, or other components. 3. Verify the servo motor and drive parameters for the slave axis are properly configured, including gains, torque limits, and acceleration/deceleration settings. 4. Monitor the actual position and velocity of the master and slave axes during operation to identify any discrepancies or oscillations. 5. Perform a servo tuning procedure to optimize the servo loop parameters and improve the synchronization between the master and slave axes. 6. If the issue persists, consult the Fanuc documentation or contact a Fanuc technical support representative for further assistance.

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FANUC Controller

Servo/Axis · Intermediate · 30-60 minutes

Alarm 407

Fanuc Alarm 407 - SERVO ALARM: EXCESS ERROR

Fanuc Alarm 407 occurs when the position deviation between synchronized axes exceeds the allowable limit defined in parameter 1886. This indicates one axis in the synchronized pair is unable to maintain positional synchronization with the master axis, commonly due to mechanical binding, servo tuning mismatch, or amplifier/motor issues on one of the axes.

FANUCServo/AxisIntermediate30-60 minutes

407

Fanuc Alarm 407 - SERVO ALARM: EXCESS ERROR

Excess Error

Root Cause Summary

Fanuc Alarm 407 occurs when the position deviation between synchronized axes exceeds the allowable limit defined in parameter 1886. This indicates one axis in the synchronized pair is unable to maintain positional synchronization with the master axis, commonly due to mechanical binding, servo tuning mismatch, or amplifier/motor issues on one of the axes.

Safety

Check for collision
Electrical Hazard: Power down and lock out the machine before performing any electrical troubleshooting. High voltages are present in the servo drives and motors.
Mechanical Hazard: Be aware of moving parts when inspecting the machine. Keep hands and clothing clear of the axis during movement.
Crushing Hazard: Ensure the axis is properly supported before disconnecting any mechanical components. The axis may move unexpectedly due to gravity.
Consult the machine's safety documentation before performing any maintenance or troubleshooting.
Wear appropriate personal protective equipment during inspections

Causes and Fixes

1
Access SYSTEM > PARAM and verify parameter 1886 (synchronous position deviation limit). Typical values range from 100-500 depending on application. Check if value is too restrictive for actual mechanical tolerances.
2
Verify parameters 1902 (synchronous axis number), 1903 (synchronous control type), and 1904-1906 (synchronous control settings) match the machine specification. Confirm both axes are properly identified in synchronization pairs.
3
Compare servo gain parameters between synchronized axes: P1825 (position gain), P1826 (velocity loop gain), P1827 (velocity integral time constant). Gains should be matched for similar tracking performance.
4
Check DIAGNOSIS > SERVO > position deviation screens (diagnoses 300-307 for each axis). Compare the actual deviation values between synchronized axes during alarm occurrence to identify which axis is lagging.

DIY Feasiblehigh confidence

Call a technician if:

·Mechanical binding requires major component replacement
·Encoder replacement needed
·Servo amplifier hardware failure suspected

Prevention

Regular lubrication maintenance
Periodic servo parameter backup
Monitor position deviation trends
Keep encoder cables properly secured

Common Mistakes

Setting EXCESS ERROR parameter too high compromising accuracy
Ignoring mechanical wear indicators
Not comparing parameters between synchronized axes
Adjusting only one axis when both need tuning

Related Alarms

408 410 411 414

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