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Navigate to DIAGNOSIS > SERVO > screen and observe the current position error for the affected axis. Record the magnitude of the error value.

Manually move the axis with servo power OFF (emergency stop active or via MPG in handle mode). Check for abnormal resistance, grinding, or binding throughout the entire axis travel range.

Ensure machine is in safe state and all personnel are clear before manual movement

Inspect ballscrew, linear guides, way covers, and coupling for crash damage, debris, insufficient lubrication, or loose mounting bolts. Check brake operation if axis is vertical.

If external load is suspected, disconnect the motor from the ballscrew coupling and rotate motor shaft manually to verify motor and encoder are free. If motor is free, issue is mechanical on machine side.

Tag and document coupling alignment before disassembly for reassembly reference

Check DIAGNOSIS > SERVO > screen for encoder feedback values. Observe if position feedback is stable or shows erratic counting when axis is stationary.

Verify encoder cable connections at both motor and amplifier. Inspect encoder cable for damage, pinching, or routing near high-voltage cables. Check amplifier LED display for encoder alarm codes (E0-E9 series on alpha series amplifiers).

Navigate to DIAGNOSIS > PARAMETER and check encoder diagnostic parameters: #300-#302 (serial encoder alarms). For absolute encoders, verify battery voltage at encoder (typically >3.0VDC) and check Parameter 1815 bit settings.

If encoder is suspect, swap encoder cable or motor with a known good axis if possible. If alarm follows the motor/cable, replace the defective component. Re-establish reference position after encoder replacement.

Absolute encoder replacement requires battery backup procedure and position data backup before disconnection

Navigate to SYSTEM > PARAM and check Parameter 1828 for the affected axis. Typical values are 5000-32767 detection units (depends on system resolution). Compare with other axes and OEM specifications.

Check Parameter 1825 (in-position check width) and Parameter 1826 (arrival position width). Verify these are consistent with machine mechanical characteristics and not set excessively tight.

Review servo tuning parameters: Parameter 2020-2024 (position/velocity loop gains) and Parameter 2040-2048 (load inertia ratio). Verify these match amplifier auto-tuning results or OEM specifications.

Do not modify servo gain parameters without baseline documentation and proper tuning procedure

If parameters appear incorrect or have been recently modified, restore from OEM parameter backup. If no backup exists, incrementally increase Parameter 1828 by 20% and test. Investigate why excessive error exists rather than simply masking with higher limit.

Increasing error limits without addressing root cause may allow machine damage to occur undetected