What causes FANUC alarm 5002?

Spindle drive fault preventing speed regulation — check spindle amplifier for fault codes. Spindle encoder signal degraded causing incorrect speed feedback to the drive. Mechanical load too high for the commanded speed — tooling or material issue. Spindle V-belt worn or slipping on belt-driven machines. Speed deviation parameter set too tightly for the application. Spindle motor winding degradation causing reduced torque output.

How do I fix FANUC alarm 5002?

1. Check the spindle amplifier for fault codes — the amplifier fault typically precedes the PS5002. 2. Monitor actual spindle speed at a low, unloaded RPM and compare to commanded — large deviation confirms mechanical or drive issue. 3. Inspect V-belt condition and tension if the machine is belt-driven. 4. Reduce cutting load and retry — if the alarm clears, the spindle is being overloaded. 5. Check spindle encoder cable and connector condition. 6. Review Fanuc spindle parameters 4900-4910 for the speed deviation tolerance settings.

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FANUC Controller

Spindle · Intermediate · 30-90 minutes

Alarm 5002

Fanuc 5002 - Spindle Speed Mismatch

Alarm 5002 occurs when the spindle encoder feedback indicates the actual RPM differs from the commanded speed by more than the tolerance set in parameters 3741/3772. This mismatch can result from mechanical binding, drive system faults, encoder feedback issues, or incorrect parameter settings that prevent the spindle from tracking commanded speeds accurately.

FANUCSpindleIntermediate30-90 minutes

5002

Fanuc 5002 - Spindle Speed Mismatch

SPINDLE SPEED MISMATCH

Root Cause Summary

Alarm 5002 occurs when the spindle encoder feedback indicates the actual RPM differs from the commanded speed by more than the tolerance set in parameters 3741/3772. This mismatch can result from mechanical binding, drive system faults, encoder feedback issues, or incorrect parameter settings that prevent the spindle from tracking commanded speeds accurately.

Safety

Do not override spindle speed alarms — spindle motor damage can result

Causes and Fixes

1
Check spindle encoder cable connections at both the encoder and spindle drive/control. Look for loose connectors, damaged pins, or cable wear at flex points.
Lock out machine power before disconnecting encoder cables to prevent electrical shock.
2
Inspect encoder optical window for contamination (oil mist, coolant, metal dust). Clean with lint-free cloth and appropriate cleaner if dirty.
3
Monitor encoder feedback signals on the spindle amplifier diagnostics screen or parameter display (actual speed display). Verify signal is present and stable during manual spindle rotation.
4
If encoder signals are absent or erratic, replace spindle encoder. Perform encoder setup and calibration per Fanuc maintenance manual after replacement.

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