FANUC 0i-F SV0410 on Z-axis: Excess Error at Stop, only on vertical axis?
I'm getting a FANUC SV0410 alarm on my CNC machine, specifically on the Z-axis. It only happens when the machine is stopped, and it's always the Z-axis. Other axes are fine. What should I check first?
A FANUC SV0410 (EXCESS ERROR (STOP)) alarm on a FANUC 0i-F controller means the Z-axis drifted from its commanded stop position, exceeding the limit in parameter 1829. Since it's only on the vertical Z-axis, the most common cause is related to gravity, the motor brake, or the counterbalance system.
Likely causes and checks
1Z-axis brake or counterbalance issue
- Points to it
- This alarm occurs only on the vertical (gravity-loaded) Z-axis, typically at servo-on or after an E-stop release. The axis might visibly drop slightly.
- Check
- Isolate and lock out power. Check the motor brake for proper operation and release. Verify that any counterbalance system (e.g., pneumatic or spring-loaded) is functioning correctly and supporting the Z-axis load. Watch DGN 300 for the Z-axis while enabling servo to see if positional deviation spikes.
2External force on the Z-axis
- Points to it
- The alarm coincides with an operation that applies an external load to the Z-axis while it's supposed to be holding position, such as a clamping mechanism or workpiece contact.
- Check
- Repeat the operation that triggers the alarm and observe the Z-axis. Watch DGN 300 for the Z-axis; if it increases significantly during the external interaction, investigate and correct the mechanical interference or force application.
3Servo system unable to hold position
- Points to it
- The Z-axis might exhibit creeping or hunting at standstill, or other servo-related alarms (like SV0436 or Pulsecoder alarms) may appear in the alarm history.
- Check
- Isolate and lock out power. Inspect the power and feedback cables for the Z-axis motor and amplifier for damage or loose connections. Check the alarm history for other servo-related alarms that might indicate a deeper issue with the amplifier, motor, or feedback unit.
4Positional deviation limit (parameter 1829) set too tight
- Points to it
- The alarm appeared after a parameter or tuning change. Diagnosis data DGN 300 for the Z-axis at standstill shows values very close to the limit set in parameter 1829.
- Check
- Compare the current value of parameter 1829 for the Z-axis with the machine builder's original parameter backup. If it was recently changed, revert it to the factory setting or a known good value.
Next check: If the brake and counterbalance appear to be working correctly, carefully observe the Z-axis DGN 300 value during servo-on and at standstill to quantify the positional deviation and see if it's consistently near the parameter 1829 limit.
What it typically looks like in the data
Related questions
Describe the fault or upload a photo, and InduQT checks it against the manufacturer manuals. Share the result here when it helps someone else.