22051

Access Diagnostics > Spindle > Reference Mark Signals in SINUMERIK HMI and monitor the digital input state during manual spindle rotation. Verify the sensor output toggles as the reference mark passes the sensor head.

Ensure spindle is at zero speed and secure before manual rotation.

Check physical alignment of the reference mark sensor using a feeler gauge (typically 1-2mm gap). Compare against machine manual specifications and re-seat connector at spindle control cabinet.

Verify sensor wiring assignment in NCK > Parameter > Axis-Specific > Spindle %2 > Reference Mark Input and confirm correct I/O address maps to active sensor channel.

If sensor is confirmed faulty, replace with equivalent part (e.g., Siemens 6FX2 series proximity switch) and recalibrate sensor gap according to OEM documentation.

Navigate to NCK > Parameter > Axis-Specific > Spindle %2 > MD 34060 and note the current REFP_MAX_MARKER_DIST value (typical range 360–3600 degrees depending on spindle type).

Manually rotate the spindle from its current position and measure the actual angular distance to the reference mark using a dial indicator or encoder readout. Compare this distance against MD 34060.

Ensure spindle motor is disabled and machine is locked before manual rotation.

If measured distance exceeds MD 34060, increase MD 34060 to at least 1.2× the measured worst-case distance. For example, if the reference mark is 450° away in the worst case, set MD 34060 ≥ 540°.

Download updated parameters to the NCK using NCK > Parameter > Download and retry the SPOS command to confirm alarm clears.

Access Diagnostics > Spindle > Encoder Status and verify the encoder type (ABS/INC) and current position feedback value. Check for encoder error flags or communication loss indicators.

Inspect spindle encoder cable routing and connectors at the spindle motor (typically SubD or M12 connector) and spindle control module. Look for pinched, corroded, or loose connections.

If using an absolute encoder, verify MD 34061 SPIND_REFP_SYNC_TOLERANCE (sync tolerance) is not too strict. If sync errors persist, perform an encoder reset via NCK > Spindle > Referencing > Reset Encoder Signals.

Encoder reset requires spindle motor to be energized; ensure area is clear.

If alarm persists, replace the spindle encoder cartridge with an equivalent Siemens unit (e.g., 1PH8 series) and recalibrate the encoder offset using the commissioning menu NCK > Spindle > Commutation > Auto-Commutate.