A common symptom of a mis-set 1860 is a "bumping" or "jerky" motion when the axis reverses direction during a G01 move combined with rapid traverse (G00) segments. If you suspect a problem, start by verifying Parameter 1861 as well—the dual position feedback amplitude interacts with the acceleration value.
If you disconnect the motor from the ball screw, the physical relationship between the encoder and the machine zero changes.
In practice, for direct drive systems: $$ 1860 = \textReference Counter (1821) \div \textScrew Pitch (in pulses) $$ (Note: This varies heavily depending on whether the machine uses a Decimal Input method or the older Integer Input method.)
| Parameter | Function | When Active | Typical Range | | :--- | :--- | :--- | :--- | | | Cutting feed ACC/DEC time constant | G01, G02, G03 | 20–200 ms | | 1620 | Rapid traverse (G00) ACC/DEC time constant | G00 | 50–500 ms | | 1622 | Rapid traverse DEC time constant (linear) | G00 (end of move) | 0 (off) to 500 ms | | 1825 | Servo loop gain (Position loop gain) | All motions | 30–200 (1/sec) | fanuc parameter 1860 full
An incorrect setting in Parameter 1860 will result in the machine moving an incorrect distance (e.g., commanding 100mm but moving 50mm or 200mm), rendering the machine unable to perform accurate machining or threading.
In essence, Parameter 1860 is the machine’s internal "truth"—a raw digital heartbeat that tells the system exactly where it is in the physical world, long before those numbers are translated into the user-friendly coordinates we see on the screen.
value used to adjust the zero point after a reference return. Maintenance & Troubleshooting Read-Only Nature A common symptom of a mis-set 1860 is
In FANUC CNC systems, functions as the Grid Shift Value for Absolute Position Coders (APC) . This parameter allows field technicians and maintenance engineers to offset the physical reference position (machine zero) without mechanically moving the encoder housing or decoupling the motor shaft.
Unplugging the encoder cable or replacing the motor/encoder resets the stored position.
It is important to note that the function of Parameter 1860 can vary by control series and software version. In some FANUC documentation, it is also described as the "First acceleration for Two-Stage Backlash Acc. function". Backlash acceleration is a feature to improve the response of an axis when it reverses direction. By defining a first acceleration value, the control can "kick" the axis more aggressively out of a reversal point to overcome mechanical play, then settle into a smoother acceleration profile. In practice, for direct drive systems: $$ 1860
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
Absolute encoders rely on a backup battery to "remember" their position when the power is off. If the battery dies, the position is lost.
