410

Navigate to DIAGNOSIS screen > Servo Monitor and observe parameter 300 (position deviation) for the alarmed axis. Normal at-rest deviation should be within ±20 pulses. Values consistently above 50-100 pulses indicate mechanical issues.

Power off the machine and manually move the alarmed axis through its full travel range. Feel for binding, unusual resistance, or tight spots indicating way problems, ballscrew damage, or bearing failure.

Lock out machine power and relieve hydraulic/pneumatic pressure before manual movement per OSHA standards

Check Parameter 1826 (in-position check width) for the alarmed axis. Typical values are 50-200 depending on system resolution. Verify Parameter 1825 bit 4 (APZ) is enabled for in-position checking.

Inspect amplifier current display via DIAGNOSIS screen > Servo Load Monitor (parameter 436). Excessive current (>70% rated) at standstill indicates mechanical overload requiring maintenance on ways, ballscrews, or linear guides.

Access SYSTEM > PARAM and verify Parameter 1825 (position loop gain) for alarmed axis. Typical range is 2000-4500 (20.00-45.00 rad/s) for standard servo systems. Compare to known good axis or OEM documentation.

Check Parameters 1820 (velocity loop gain 1st), 1821 (velocity loop integral time constant 1st). Typical 1820 values: 30-60, typical 1821 values: 30-200ms. Verify Parameter 1960 (load inertia ratio) matches actual mechanical load (typically 30-100%).

Perform servo tuning verification by navigating to MAINTENANCE > Servo Tuning screen. Execute auto-tuning function (if available on your control series) or manually increase Parameter 1825 by 10% increments while monitoring position deviation on Diagnostic screen 300.

Increase gains cautiously - excessive gain causes oscillation and potential mechanical damage. Monitor for vibration or servo alarm 401

Verify Parameter 1827 (excess error detection width at servo off) is set appropriately (typically 500-2000). Check that Parameter 1815 bit 0 (OVC - overshoot detection) is not inadvertently enabled causing premature alarm triggering.

Check servo amplifier LED status codes on the alarmed axis amplifier. Solid green = normal, flashing patterns indicate faults. Consult amplifier manual for LED diagnostic codes. Record any non-standard patterns before proceeding.

Navigate to DIAGNOSIS screen and monitor parameters 410-413 (encoder feedback signals A/B/Z phases). Verify clean pulse counts with no erratic jumps during slow jog movement. Also check parameter 800 (encoder serial data) for serial pulse coder systems (α/β series).

Inspect encoder cable connections at both motor and amplifier ends. Check for bent pins, cable damage, contamination, or shield ground continuity. Verify cable routing away from high-voltage motor power lines and spindle cables to prevent EMI interference.

Use proper ESD precautions when handling encoder connections - static discharge can damage encoder circuitry

Perform encoder battery check via DIAGNOSIS screen parameter 305 (absolute encoder battery voltage). Should read >3.0VDC. If below 2.8VDC or alarm 911 history exists, replace encoder battery per Fanuc procedure and re-establish reference position.