FANUC 0i-F SV0411 on Z-axis during rapid traverse, what to check?
I'm getting a FANUC SV0411 alarm on my 0i-F controller, specifically on the Z-axis. It happens consistently during rapid traverse at the start of a program. What should I check first?
The SV0411 (EXCESS ERROR (MOVING)) alarm on a FANUC 0i-F controller indicates that the positional deviation of an axis while moving exceeded the limit set in parameter 1828. This means the motor couldn't keep up with the commanded motion, causing the control to stop. Since it occurs during rapid traverse, the highest position error is likely being encountered.
Likely causes and checks
1Mechanical binding or a crash
- Points to it
- A mechanical issue like binding or a previous crash can restrict axis movement, causing the motor to fall behind the commanded position, especially during high-speed moves like rapid traverse.
- Check
- With the Z-axis isolated and locked out, manually check that the ballscrew, coupling, and ways move freely. Also, ensure that the way covers are not jammed with chips or debris. Listen for any rough or noisy movement when jogging slowly.
2Motor brake not releasing
- Points to it
- If the motor brake on the Z-axis (a vertical axis) is not fully releasing at the start of the move, it will impede motion and cause an immediate excess error as the motor tries to move against the brake.
- Check
- Verify that the brake releases when the servo is enabled. Check the brake supply voltage and wiring according to the machine builder’s electrical diagrams.
3Load or acceleration beyond the motor’s capability
- Points to it
- If the Z-axis is experiencing a load or acceleration that exceeds the motor's capacity, it will struggle to maintain the commanded position, leading to an excess error, particularly during fast rapids.
- Check
- Compare the value of Diagnosis Data (DGN) 300 during the rapid traverse move with the setting in parameter 1828. Review the programmed feedrate, acceleration settings, and any cutting conditions that might precede the rapid move.
4Parameter mismatch
- Points to it
- Incorrect parameter settings, especially for rapid rate or servo loop gain, can cause the system to command movements that the motor cannot achieve within the allowed positional deviation.
- Check
- Compare parameters 1828, 1825, and the rapid rate setting with the machine builder’s backup parameters. FANUC guidelines suggest setting 1828 based on the rapid rate and servo loop gain with a margin of about 1.2.
Next check: Since the alarm occurs right at the start of the first move (rapid traverse) and on a vertical axis, I would first investigate the Z-axis mechanics for binding and then check the motor brake release.
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