In a semi-closed loop setup, position feedback comes directly from the serial encoder built into the back of the FANUC servomotor. For standard FANUC Pulsecoders (e.g., αialpha i
When performing a manual reference position return (e.g., G28 or manual ZRN): fanuc parameter 1860 full
, then counter capacity = 4000 pulses. The CNC will think one motor rev = 4000 pulses, causing the reference point to occur twice per physical motor revolution → unstable grid. In a semi-closed loop setup, position feedback comes
| Parameter | Name | Purpose | | :--- | :--- | :--- | | | Grid Shift (Reference Position) | Shifts the grid point for all reference returns. Used for mechanical dog adjustment. | | 1851 | Grid Shift Fine | Fine adjustment (usually in 1/1000 mm or 1/100000 inch increments). | | 1860 | Reference Position Shift | Shifts the position the machine considers "Zero" after the reference return is complete. Often used with Absolute Pusle Coders. | | Parameter | Name | Purpose | |
When the procedure completes successfully:
Reference position updating is performed . When the machine coordinate values cross the threshold defined in Parameter 1860, the system automatically runs a reference position update using either the 0-degree marker or the rounding value specified in Parameter 1260 (typically 360 degrees).