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Remove the current tool and tool holder from the spindle. Inspect taper surfaces for chips, debris, or damage. Clean both spindle taper and tool holder taper with solvent and lint-free cloth.

Ensure spindle is locked out and cannot rotate during inspection.

Install a known-good master tool holder without a tool. Reset alarm and test spindle at progressively higher speeds (25%, 50%, 75%, 100% of typical operating speed) while monitoring for vibration or alarm recurrence.

If alarm clears with master holder, check the original tool for balance issues. Verify tool is properly seated in holder, retention knob torque is correct, and tool assembly is balanced for the intended speed range.

Inspect drawbar mechanism and Belleville springs for proper engagement. Verify drawbar pull force meets manufacturer specifications using a drawbar force gauge (typically 1800-2400 lbs depending on taper size).

With spindle stopped and locked out, manually check for radial play by grasping a tool holder installed in spindle and attempting to move it perpendicular to spindle axis. Any perceptible movement indicates bearing wear.

Use LOTO procedures before manual spindle inspection.

Review spindle bearing temperature sensors in PMC ladder or maintenance screen. Compare current temperatures to historical baseline values. Temperatures 15-20°C above normal indicate bearing deterioration.

Run spindle at low speed (500-1000 RPM) and listen with mechanic's stethoscope at front and rear bearing locations. Grinding, rumbling, or cyclical noise patterns indicate bearing damage requiring replacement.

Use hearing protection and maintain safe distance from rotating components.

Check maintenance records for bearing service intervals. If bearings exceed manufacturer recommended hours (typically 8000-15000 hours depending on duty cycle), schedule spindle rebuild or bearing replacement.

Access spindle parameters and verify vibration detection threshold (parameter varies by drive model, typically 4200-4299 range). Compare against OEM specifications. If recently changed or outside normal range (usually 20-50% threshold), restore to default.

Document all parameter values before making changes.

Inspect spindle motor encoder cable for damage, proper shielding, and secure connections at both motor and drive. Check for oil contamination on encoder itself. Use oscilloscope to verify clean encoder signals (A, B, Z phases) without noise or dropouts.

Review spindle load meter during acceleration and constant speed operation. Erratic current draw (>15% fluctuation) without load changes indicates electrical issues in motor windings, drive output stage, or feedback loop.

If drive was recently serviced or replaced, perform auto-tuning procedure per Fanuc spindle setup manual. Improper gain settings can cause oscillation detection. Verify all spindle drive parameters match motor nameplate specifications.

Auto-tuning requires spindle to run unloaded. Ensure work area is clear.