Fanuc · Alpha i Series AC Servo Motor and Spindle
No absolute position is established within 5 turns immediately after communication between the spindle amplifier and sensor is started. This indicates a failure to detect the absolute reference mark.
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Verify the proper connection and alignment of the spindle sensor (e.g., αi position coder, αiBZ sensor, αiCZ sensor).
Ensure the sensor ring is not deformed or damaged, particularly the Z-phase generation section.
Check for mechanical backlash between the spindle and detector, as this can affect one-rotation signal detection.
If the sensor head was moved, perform the procedure applicable when the sensor head is moved after conduction (Section 11.1.1.6 or 11.2.3.9).