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Check amplifier LED status on the specified axis servo drive. Solid red LED indicates overcurrent/overload condition. Verify alarm history in DIAGNOSIS screen (SYSTEM > ALARM > HISTORY) for concurrent alarms like 410 (overload) or 414 (excess error).

Manually rotate the axis with the machine in emergency stop or motors disabled. Feel for binding, rough spots, or abnormal resistance throughout the full travel range. Check for crash damage to couplings, ballscrew, or linear guides.

Ensure machine power is off and axis brakes are released before manual movement

Navigate to DIAGNOSIS > SERVO screen and monitor parameters 300-307 (servo load meter for each axis). Values consistently above 70-80% under normal cutting indicate mechanical issues or improper load matching. Compare to load during rapid traverse versus cutting.

Inspect ballscrew lubrication, check for contamination in guideways, verify coupling tightness, and check motor mounting bolts. Re-adjust backlash compensation if mechanical repairs were recently performed (parameters 1851, 1852 for lost motion compensation).

Check encoder cable routing for damage, pinching, or proximity to high-voltage cables causing EMI. Inspect encoder connector at motor and amplifier for bent pins, corrosion, or loose connection. Verify cable shield continuity and proper grounding.

Monitor encoder signals in real-time: Navigate to DIAGNOSIS > SERVO > position display and observe DGN 300 (current position) and DGN 308 (position deviation). Jog axis slowly and watch for position count jumps or erratic feedback indicating encoder issues.

Check encoder-specific diagnostics: DGN 390-397 shows encoder status bits. Bit errors indicate communication problems. For serial encoders (αi series), verify parameters 2000-2023 (encoder type and settings) match motor specifications exactly.

If equipped with absolute encoder, perform reference position return and battery check. Low battery (check DIAGNOSIS > PMC > KEEP RELAY status) can cause encoder initialization errors. Replace encoder if contamination or bearing roughness detected in motor.

Replacing encoder requires parameter backup and may need new position reference establishment

Verify parameter 1828 (speed coincidence detection time) is not set too aggressively low. Default is typically 200-300ms. Also check parameter 1829 (allowable speed difference) - typical value 1000-2000 (units depend on parameter 1006 setting). Temporarily increase 1829 by 50% to test if alarm threshold is marginal.

Increasing tolerance masks underlying problems; use only for diagnostic confirmation

Compare current servo parameters against machine builder defaults or backed-up working values. Check SYSTEM > PARAM > SERVO parameters 2020-2024 (velocity loop gain), 1825 (position loop gain), 1826-1827 (feedforward gains). Recent parameter changes or battery-dead parameter loss often cause this alarm.

Perform automatic servo tuning if available on your system: Set parameter 2680 (auto-tuning mode) for the affected axis. Execute auto-tuning routine from SYSTEM > SERVO menu. This recalculates optimal gains for current mechanical load and inertia ratio.

Ensure axis moves freely and no workpiece/fixture is mounted during auto-tuning

Check parameter 2022 (velocity loop integral time constant) and 2023 (integral gain). Values too low cause oscillation; too high causes sluggish response. For αi servo: verify parameter 2000-2001 (motor model code) matches actual installed motor exactly - mismatch causes improper current/torque control.