26030

Access Diagnostics > Parameter > Machine Data on the 840D HMI. Navigate to MD32100 (GEARING_TYPE) and compare current value against the last known working configuration documented in your commissioning records.

Do not modify these parameters without documentation of original settings.

Verify MD32110 GEAR_RATIO_NUMERATOR and MD32120 GEAR_RATIO_DENOMINATOR values. Check the axis-specific parameters for the affected encoder (typically MD32010 ENCODER_TYPE confirms absolute encoder presence).

If parameters were intentionally changed, perform an encoder replacement procedure: use NCK > Diagnostics > Encoder Replacement mode to reinitialize the absolute position with current encoder serial number.

This clears the absolute position memory; machine must be re-referenced to a known position immediately after.

Restore original parameter values from backup if the ratio change was unintended, then cycle power to re-establish absolute position validity.

Navigate to Diagnostics > Encoders on the 840D HMI. Compare the current encoder serial number displayed for the affected axis against maintenance records. Check parameter MD32011 ENCODER_SERIAL_NUMBER if available in your system version.

If encoder serial number has changed, enter the NCK Encoder Replacement function via Diagnostics > Special Functions > Encoder Replacement. This procedure invalidates the stored absolute position and requires immediate machine re-referencing.

Encoder replacement mode must be exited by performing a reference move (e.g., via MD35400 REFP_MODE search for home) within the next PLC cycle or alarm conditions will persist.

Execute a controlled reference move to establish a new absolute position baseline. Use the axis reference pulse (typically via machine zero search function) to synchronize the encoder absolute counter with the mechanical axis position.

Do not attempt to move the axis in automatic mode until reference move is complete and alarm 26030 is cleared.

Verify the encoder serial number is now stored correctly by checking Diagnostics > Encoders display and confirm alarm 26030 no longer appears in the alarm history.

Check the NCK clock battery status via Diagnostics > System Information. A discharged backup battery (typically visible as a warning icon) can cause loss of absolute position memory. If depleted, replace the battery and allow 30 minutes for the NCK to stabilize.

System should not be powered down during battery replacement; have UPS or backup power available.

Verify parameter block consistency by accessing Program > Parameter Block Info and confirming the active parameter set matches the backup set. Re-download and activate the parameter block if mismatches are detected.

Ensure machine is in READY state and no motion is active before parameter block activation.

Clear the absolute position data by entering Diagnostics > Reset Encoder Absolute Position (if available in your software version), or use the Encoder Replacement procedure to re-initialize with the current encoder configuration.

This action requires re-referencing the axis immediately afterward.

Perform a full machine reference cycle using the automatic reference routine (typically via cycle start and machine zero search) to re-establish valid absolute position memory.