FANUC SV0411 Alarm: Excess Error During Movement and Troubleshooting

FANUC SV0411 means that the absolute value of a servo axis's position deviation exceeded the applicable limit while the axis was moving. On many FANUC controls, the English alarm text is SV0411 EXCESS ERROR (MOVING), with the affected axis shown in parentheses.

The CNC calculates position deviation from the movement command and position feedback. A normal moving axis has some following error, but the value must remain below the movement limit. For an ordinary servo axis, the relevant limit is generally parameter 1828. During rigid tapping, a separate tapping-axis movement limit may apply, such as 5310 or 5314 on older systems, or a spindle-specific parameter such as 5310, 5350, 5354, or 5358 on applicable newer systems.

Example FANUC CNC alarm screen showing SV0411 on the Y axis. The axis shown in parentheses changes with the affected machine axis.

For a wider alarm-number reference, see the FANUC SV Alarm Codes guide.

What Does FANUC SV0411 Mean?

A FANUC servo system receives position commands from the CNC and position feedback from the motor pulse coder or configured external detector. The servo error register represents the difference accumulated between commanded movement and feedback movement. This value is also called position deviation, position error, or following error.

Some position deviation is expected while an axis is accelerating, traveling, and decelerating. The servo loop uses this error to produce the torque required to follow the command. SV0411 is generated only when the absolute deviation becomes greater than the movement limit applicable to the active control condition.

The FANUC 0i-F Plus Parameter Manual B-64700EN/01 states that if movement position deviation exceeds parameter 1828, the CNC generates SV0411, EXCESS ERROR (MOVING) and stops operation immediately in the same manner as an emergency stop. FANUC also warns that an incorrectly set limit can damage the machine or workpiece.

SV0411 therefore does not identify one failed component by itself. It says that the axis did not follow its command within the permitted moving-state error. The reason may be mechanical resistance, a sudden load change, a brake that did not release, a motor-power problem, incorrect servo data, excessive commanded speed, unstable adjustment, or an amplifier fault.

SV0411 Is a Moving-State Alarm, Not a Stop Alarm

The distinction between SV0411 and SV0410 is the state in which the CNC performs the deviation comparison:

The supplied Chinese summary describes an excessive error while the axis is stopped, but that wording belongs to SV0410 in the cited FANUC manuals. The uploaded alarm screen correctly describes SV0411 as an error during movement. Diagnose the number and operating state shown by the actual control rather than relying on a translated one-line description.

For the related stopped-state alarm, see the FANUC SV0410 Excess Error at Stop guide.

Determine Which Position-Deviation Limit Applies

Do not change parameter 1828, 5313, or 5314 merely because SV0411 appears. First identify whether the axis was performing normal servo motion, rigid tapping, or another special servo control function.

On older controls such as the 0i-C covered by B-64120EN/01, parameter 5310 normally sets the tapping-axis movement limit. Parameter 5314 is an extended two-word setting used when detector resolution requires a value beyond the valid range of 5310. If 5314 is zero, 5310 remains effective; if 5314 is nonzero, it replaces 5310 for that condition.

On the 0i-F Plus covered by B-64700EN/01, 5310 is already a two-word first-spindle tapping-axis movement limit, and the separate second-, third-, and fourth-spindle values are 5350, 5354, and 5358. Parameter 5313 is defined there as the positional-deviation limit while the spindle is stopped in rigid tapping. It is not the ordinary SV0411 movement limit and must not be substituted for parameter 1828 or the tapping-axis movement setting.

Parameter numbering varies with CNC generation, software, option, number of spindles, and control mode. Use the parameter manual for the exact CNC instead of copying a value or parameter list from another machine.

1. Record Exactly When the Alarm Occurs

Before resetting the CNC, record:

• The complete SV0411 message and affected axis

• The CNC series, model, and software version

• The servo amplifier and motor models, including all suffixes

• The active mode: jog, rapid traverse, cutting feed, automatic cycle, reference return, rigid tapping, spindle positioning, or another special function

• The commanded direction, feedrate, override, and approximate axis position

• Any collision, unusual sound, vibration, delay, or lack of movement

• All simultaneous servo, pulse-coder, FSSB, overcurrent, brake, or machine alarms

• Any recent motor, amplifier, cable, parameter, CNC memory, or mechanical work

The alarm timing is highly diagnostic. An alarm that appears immediately when motion is commanded suggests a different branch from one that appears only at maximum rapid speed, under cutting load, at a repeatable machine position, or at the reversal point of rigid tapping.

If the control and amplifier support FANUC's trouble-diagnosis guidance, preserve the sampled data and open the guidance screen before repeated resets erase useful evidence. FANUC maintenance documentation uses SV0411 as an example for this function.

2. Observe the Position Deviation Before Changing the Limit

On applicable FANUC systems, diagnosis 300 displays the servo position deviation for each axis. Observe the affected axis while following the safe test procedure specified by the machine builder. Determine whether the deviation:

• Rises immediately even though the axis does not move

• Increases mainly during acceleration

• Becomes excessive only above a certain feedrate

• Spikes at one physical position

• Changes sharply when cutting load is applied

• Oscillates with visible or audible vibration

• Becomes excessive when rigid tapping reverses direction

Compare the measured behavior with the current verified parameter and the machine's known-good data. Parameter 1828 is not an arbitrary tolerance for finished-part accuracy. FANUC bases its normal setting on the position deviation expected at rapid traverse, considering the actual servo loop gain and detector unit, with an appropriate margin.

Back up the CNC and servo data before any authorized change. Record the original value and the reason for the change. Do not keep increasing the limit until the alarm disappears. That approach allows a larger following error before the safety stop and can conceal a mechanical, brake, wiring, motor, or control problem.

3. Check Mechanical Load and Axis Resistance

FANUC's servo-amplifier trouble-diagnosis guidance lists a large load change as one possible cause of SV0411. Inspect the complete transmission and machine movement before assuming that the electronics are defective.

Check for:

• A collision, workpiece, fixture, tool, chip accumulation, or guard obstructing motion

• Poor lubrication, a binding ballscrew, damaged bearing, tight guideway, or seized transmission component

• A loose coupling, slipping connection, or damaged gearbox component

• Excessive cutting force, an unsuitable tool, or a sudden process-load increase

• A problem that occurs repeatedly at the same axis position

• Abnormal load on a vertical, inclined, rotary, or counterbalanced axis

Test only within a safe area and at a controlled speed. If the axis does not move after a command, do not continue commanding it against a possible obstruction. The growing position deviation can reach the SV0411 limit while the motor and amplifier are producing high torque.

4. Verify That the Brake or Clamp Releases Correctly

FANUC specifically lists brake failure as a possible cause of SV0411. This is especially relevant to vertical axes, rotary axes, and servo axes fitted with a holding brake or mechanical clamp.

Confirm the machine builder's release sequence, coil voltage, hydraulic or pneumatic pressure where applicable, mechanical release, feedback signal, and timing. A brake may release partially, release too late, drag under load, or remain applied because of a ladder, output, wiring, power-supply, or mechanical problem.

Do not bypass the brake or remove a safety interlock merely to clear the alarm. A vertical or gravity-loaded axis can fall or move unexpectedly. Brake diagnosis must follow the machine builder's procedure and be performed by qualified personnel.

5. Check Commanded Speed and Machine Specification

The βi-B servo-amplifier maintenance manual lists a commanded speed exceeding the specification among the possible SV0411 causes. This does not mean that every high-feed alarm should be solved by permanently reducing the feedrate.

Confirm the programmed feed, rapid-traverse setting, override, gear or transmission condition, motor maximum speed, detector resolution, command multiplier, flexible feed gear, and machine-specific axis limits. If the alarm disappears only at reduced speed, use that result to locate the inability to follow at higher demand. Possible reasons include mechanical resistance, insufficient torque, incorrect motor data, a motor-power problem, unsuitable acceleration, or an incorrect limit calculation.

Retest at high speed only after the axis has been proven mechanically safe and all relevant settings have been verified.

6. Inspect the Motor Power Circuit and Motor Windings

FANUC's official trouble-diagnosis list includes both a short circuit and a disconnection in the power cable or motor winding. With machine power isolated and the DC link fully discharged, inspect:

• Motor power connectors, terminals, pin condition, and cable continuity

• Loose, damaged, overheated, or broken conductors

• Correct U/V/W connection and axis assignment

• Motor winding continuity and phase balance

• Insulation to ground using the procedure and test equipment approved for the installed motor

• Cable damage caused by flexing, coolant, chips, crushing, or recent service work

Do not perform insulation testing through a connected amplifier or pulse coder. Disconnect and protect sensitive electronics according to the FANUC motor manual. A low insulation reading, phase imbalance, or intermittent open circuit requires repair of the confirmed defective cable or motor; it is not corrected by changing parameter 1828.

7. Verify Power and Feedback Cable Assignment After Maintenance

If SV0411 started after cabinet, amplifier, motor, or cable work, confirm that the power and feedback cables are connected to the correct axis and amplifier channel. Two connectors can be fully seated yet assigned to the wrong motors.

Check connector identity, axis labels, keying, pin condition, shielding, grounding, and routing against the electrical drawings. When two axes alarm together after maintenance, exchanged motor-power or feedback cables are an important possibility.

SV0411 alone is not a dedicated pulse-coder disconnection alarm. Inspect the encoder and feedback cable more aggressively when the alarm began after feedback work, feedback values are implausible, connectors are loose or damaged, or a simultaneous detector alarm is present. Diagnose any pulse-coder alarm by its own number rather than treating every SV0411 as proof of encoder failure.

8. Check the Servo-Off Signal and Machine Sequence

FANUC also lists a malfunction of the servo-off signal as a possible SV0411 cause. If the machine removes motor excitation while the CNC continues issuing position commands, feedback motion cannot follow the command and the position deviation can increase rapidly.

Review the machine ladder and I/O timing for the affected axis. Look for a servo-off request that changes unexpectedly during motion, a loose field signal, an incorrect interlock, a clamp or mode transition that removes excitation too early, or an output that was modified during service.

Do not force the servo-off signal or bypass the machine's safety sequence. Identify why the signal state disagrees with the commanded operating state and correct the ladder, field input, wiring, or machine condition responsible.

9. Verify Servo Parameters and Any Recent Initialization

Incorrect motor identification, detector data, direction, velocity-feedback data, position-feedback data, flexible-feed-gear settings, loop gain, acceleration/deceleration, or machine-specific servo values can prevent the axis from following correctly.

Compare the active data with a verified backup for the exact machine, motor, amplifier, detector, and axis. Servo initialization should be considered only when parameters were lost, corrupted, loaded from another machine, or intentionally changed during replacement work. Reinitialization can overwrite critical data and is not a harmless reset.

If initialization is necessary, preserve all existing CNC and servo data, use the exact FANUC procedure and correct motor code, restore the machine builder's axis-specific values, then commission and reference the axis according to the machine documentation.

10. Correct Vibration, Resonance, or Unstable Servo Adjustment

If the axis vibrates, hunts, or produces an abnormal sound during motion, the growing deviation may be a consequence of unstable servo control. Check mechanical looseness, resonance, load inertia, coupling condition, detector mounting, gain, filters, and recent tuning changes.

Do not randomly lower gain, copy tuning values from another axis, or change resonance parameters without waveform evidence. First identify whether the instability is mechanical, feedback-related, or adjustment-related. Compare torque, speed, and position-deviation behavior with the machine builder's approved data and a known-good axis where appropriate.

11. Verify a Repaired or Rewound Servo Motor

The technician-supplied phase-sequence check is relevant when the motor was disassembled, rewound, had coils or internal leads replaced, or has an uncertain repair history. Qualified servo personnel should verify the phase relationship, pulse-coder alignment, motor identification, winding condition, insulation, brake wiring, and feedback relationship against the correct FANUC specification.

Do not exchange motor phases as a trial. FANUC servo control depends on the correct relationship between commanded current and rotor-position feedback. Trial-and-error phase changes can cause uncontrolled motion, overcurrent, motor damage, or additional alarms.

12. Test the Servo Amplifier After External Causes Are Checked

FANUC includes amplifier failure among the official SV0411 possibilities. An amplifier may fail to produce the required current, lose one output phase, remove excitation incorrectly, or control the motor abnormally. However, SV0411 by itself does not prove that the amplifier is defective.

Review the amplifier status and all simultaneous alarms. Verify the mechanical system, brake, motor power circuit, motor, feedback assignment, servo-off sequence, and parameters before replacing the drive. If a substitution test is required, use an exact compatible amplifier and preserve the original servo configuration. Select the unit by complete model and suffix, not only by appearance or rated output.

REACO CNC can help test, repair, or select compatible FANUC servo, spindle, and power drives.

Rigid-Tapping-Specific SV0411 Checks

When SV0411 occurs only during rigid tapping, identify whether the excessive deviation belongs to the tapping axis or the spindle and whether it occurs during feed, deceleration, or reversal. Then confirm:

• The selected first, second, third, or fourth spindle

• The exact movement-limit parameter used by that CNC generation

• Whether an older system uses 5310 or a nonzero 5314 extended value

• Whether a newer system uses 5310, 5350, 5354, or 5358 for the selected spindle's tapping axis

• The spindle and tapping-axis loop gains, acceleration/deceleration, gear ratio, and detector resolution

• The programmed thread pitch, feedrate, spindle speed, tapping depth, and return conditions

• Mechanical freedom of the tapping axis and spindle at the alarm point

• The position-deviation and synchronization diagnostic values supported by the control

Do not use parameter 5313 as the tapping-axis movement limit without an exact manual stating that meaning for the installed CNC. In the cited 0i-C and 0i-F Plus manuals, 5313 is associated with the spindle stopped state, while 5314 on the older 0i-C is an extended tapping-axis movement limit.

FANUC SV0411 Diagnostic Table

Recommended Troubleshooting Order

1. Record the complete SV0411 message, affected axis, motion type, direction, speed, alarm history, and simultaneous alarms.

2. Determine whether the event occurred during ordinary servo motion, rigid tapping, or another special servo control mode.

3. Preserve the current parameters and sampled diagnostic data before resetting or editing anything.

4. For ordinary motion, compare the position deviation with parameter 1828. For rigid tapping, identify the selected spindle and the exact movement-limit parameter used by that CNC generation.

5. Inspect the axis for collision, binding, poor lubrication, local resistance, sudden load change, or abnormal cutting load.

6. Verify that any brake or clamp releases completely and at the correct time.

7. Confirm that the commanded speed, acceleration, motor data, and machine specification are compatible.

8. With power safely isolated, inspect the motor power cable, winding continuity, insulation, and correct axis assignment.

9. Check feedback connections when service history, diagnostic behavior, or simultaneous detector alarms provide evidence.

10. Review the servo-off signal and machine sequence for an unexpected loss of excitation during motion.

11. Compare servo parameters with the verified machine backup; initialize only when justified and with complete machine data.

12. Diagnose vibration or resonance before changing gain or filter parameters.

13. If the motor was repaired or rewound, have its phase and feedback relationship professionally verified.

14. Test or replace the servo amplifier only after the external causes and configuration have been checked.

15. Retest first at a safe speed and no load, then complete the machine builder's full functional verification.

Technical References

• FANUC Series 0i-MODEL F Plus Parameter Manual, B-64700EN/01, parameters 1828, 5310, 5311, 5312, 5313, 5350, 5354, and 5358

• FANUC Series 0i-MODEL C / 0i Mate-MODEL C Parameter Manual, B-64120EN/01, parameters 5310 through 5314 and second-spindle rigid-tapping limits

• FANUC Series 0i-MODEL D / 0i Mate-MODEL D Maintenance Manual, B-64305EN/03, SV0411 alarm description

• FANUC AC Servo Motor βi-B/βi Series, AC Spindle Motor βi Series, Servo Amplifier βi-B Series Maintenance Manual, B-65425EN/02, SV0411 trouble-diagnosis guidance

• Applicable FANUC servo motor, servo amplifier, connection, parameter, and maintenance manuals for the installed equipment

Always use the manual edition that applies to the exact CNC, software, servo motor, amplifier, detector, rigid-tapping configuration, and machine. Parameter modification, powered testing, insulation measurement, motor wiring work, and drive replacement must be performed by qualified personnel under the machine builder's safety procedure.

Need Help With FANUC SV0411 Alarm?

REACO CNC provides independent FANUC alarm analysis, servo amplifier testing and repair, motor and feedback-system checks, parameter compatibility support, and replacement-drive supply. Send us the complete alarm screen, CNC model, servo amplifier model and suffix, motor model, affected axis, current parameter values, and a description of exactly when the alarm occurs.

Visit the FANUC Technical Support Center for more FANUC alarm guides, or contact REACO CNC for assistance.

Reference Source: Beijing FANUC. This article is based on FANUC technical documentation. The applicable movement-limit parameter and troubleshooting procedure depend on the exact CNC, software, servo system, detector, rigid-tapping configuration, and machine.