411

Navigate to DIAGNOSIS screen and monitor position deviation in real-time. Press SYSTEM > DIAGNOSIS > select diagnostic number 300 for axis position deviation display. Observe the deviation value during jog motion - should typically be under 50-100 encoder pulses during normal feed.

Check Parameter 1826 (in-position check width) and Parameter 1829 (excess error detection level). Typical 1829 value is 5000-10000 encoder pulses. If set too low, increase incrementally by 20% for testing only - do not use as permanent fix.

Increasing Parameter 1829 masks the problem and may allow crashes. Use only for diagnostics to confirm root cause.

Manually rotate the axis by hand with servo OFF (emergency stop active). Check for abnormal friction, binding points, or mechanical resistance. Inspect ball screws, linear guides, and coupling for damage or contamination.

Ensure all personnel are clear before manually moving axis. Verify machine is in emergency stop condition.

Review servo gain parameters: Parameter 1825 (position loop gain), 1826 (velocity loop gain), 1827 (velocity integral time constant). Compare with OEM default settings or baseline backup. If gains were recently changed or amplifier replaced, restore factory servo tuning values and re-tune using auto-tuning function if available.

Check servo amplifier LED status on the affected axis. On αi/βi series amplifiers: steady green = normal, flashing red = alarm condition, alternating red/green = communication error. Record LED pattern and cross-reference with amplifier manual.

Navigate to MAINTENANCE > SERVO > SERVO MONITOR screen. Monitor velocity feedback, current feedback, and position deviation during slow jog (10% feedrate override). Compare commanded vs actual values - look for erratic feedback or current limit saturation.

Check encoder cable connections at motor and amplifier. Inspect for damaged shielding, loose connectors, or contamination. Verify encoder feedback by checking diagnostic 410 (pulse coder alarm) history. Swap encoder cable with known good axis if possible to isolate fault.

Power down CNC completely before disconnecting encoder cables to prevent amplifier damage.

Measure DC bus voltage at amplifier. Check Parameters 2165-2169 (servo alarm history) for related faults (401 overload, 408 overvoltage, etc.). If bus voltage is unstable or amplifier shows thermal warnings, inspect amplifier cooling fans and heat sink condition.

Review NC program for excessive F codes or rapid traverse (G00) moves over short distances. Test by running program at 25% feedrate override - if alarm clears, feedrate or acceleration is likely the issue.

Check acceleration/deceleration time constants: Parameter 1620 (rapid traverse time constant), 1621 (cutting feed time constant), 1622 (acceleration after in-position). Increase these values by 50-100ms incrementally to reduce mechanical stress and position lag during acceleration.

Verify rapid traverse rate settings in Parameters 1420-1427 (rapid traverse rate per axis). Confirm these match machine mechanical specifications. If recently changed, restore to OEM values.

Monitor cutting load by checking diagnostic 492 (servo load meter) during actual cutting. Values consistently above 80% indicate excessive load. Reduce cutting parameters (depth of cut, feedrate) or check for dull tooling increasing cutting forces.