Fanuc · AC Spindle Motor Alpha i-Beta i Series Parameters
The position coder (encoder) feedback cable is disconnected or the sensor is faulty. This results in loss of position feedback, making position control impossible.
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Check physical connection of the encoder cable at both the motor and the amplifier.
Measure encoder signal integrity (e.g., A, B, Z pulses) at amplifier terminals.
Verify encoder resolution and type settings in CNC parameter P4-XX.
Test encoder output using an oscilloscope if possible.