Applicable Systems
Series 0i
Series 16/18/21
Alpha
Beta
Symptoms
The servo amplifier ready signal (MCON) is off while the CNC is commanding servo operation. Alarm SV 404 is displayed for the Z axis.
Possible Causes
- Z axis servo amplifier fault or overload
- Z axis servo motor cable damaged or disconnected
- Z axis mechanical binding or excessive load
- Servo parameter setting incorrect for this axis
Troubleshooting Steps
- Step 1: Check the Z axis servo amplifier status LEDs for alarm indication
Amplifier status LED shows alarm code if amplifier fault - Step 2: Inspect Z axis servo motor cable and connectors for damage
Cable intact, connectors properly seated - Step 3: Check Z axis mechanical system for binding or excessive load
Axis moves freely without excessive force when motor is de-energized - Step 4: Verify servo parameters for Z axis match motor and amplifier specifications
Parameters match the motor/amplifier data sheet - Step 5: Clear alarm and test axis movement at low speed
Axis moves smoothly without alarm returning
How to Reset
Power off the machine, correct the fault, power on, and press RESET. For servo alarms, always investigate the root cause before restarting to prevent damage.
Common Replacement Parts
- varies: Z axis servo amplifier or motor (if confirmed faulty) (Confirm with FANUC servo system test before replacement)
Frequently Asked Questions
- Q: What does Fanuc SV 404 Z alarm mean?
Servo Ready Off: The servo amplifier ready signal (MCON) is off while the CNC is commanding servo operation. This alarm is specific to the Z axis.
- Q: How do I clear Fanuc SV 404 alarm?
Power off the machine, investigate the servo amplifier status, check motor cables and mechanical system, then power on and clear the alarm with RESET.
Source: Fanuc 0i/0iMate Servo Alarm Code List, FANUC Corporation
Category: CNC