Fanuc Parameter 1860 _hot_ Full Jun 2026

When a machine performs a zero-return (G28) using a reference mechanical grid, Parameter 1860 dictates the size of the "grid" window. Incorrect values can cause the machine to shift its zero point by exactly one motor revolution.

After replacing a servo motor or ballscrew, the machine shakes during G01 moves. The new components have different inertia. Calculate the new inertia ratio (parameter 2047/2048) first, then reduce 1860 by 20% as a starting point, then fine-tune upward.

is defined as the Reference Position Shift Value on the Z-axis (or the axis to which it is assigned). In many standard Fanuc configurations (especially on lathes and machining centers with absolute encoders), Parameter 1860 holds the distance (in detection units) that the machine moves to find its Grid Point during a reference return operation.

There are three primary reasons a machinist or service technician modifies Parameter 1860: fanuc parameter 1860 full

: Detection Units (varies based on the machine's configured increment system, typically 0.001 mm or 0.0001 inch). The Architecture: Grid Shift vs. Position Loss

After setting or resetting Parameter 1860:

There is no universal "perfect" number for 1860. It depends on your machine's mechanical design, motor torque, and the workpiece material. However, you can calculate a safe starting point. When a machine performs a zero-return (G28) using

Officially known as the (or sometimes referred to as the linear acceleration time constant for each axis), Parameter 1860 directly controls how aggressively your machine’s axes accelerate during a cutting feed move. Getting this value wrong can lead to servo lag alarms, poor corner finishes, or even mechanical damage.

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

Positive values shift the reference position in the positive direction. Negative values shift it in the negative direction. The new components have different inertia

Common default values for standard modern FANUC encoders often default to counts/revolution internally, but the parameter initialization screen usually sets Parameter 1860 automatically based on the motor ID (Parameter 2020).

Your Fanuc servo system operates on a "Grid" generated by the position feedback device (pulse coder, absolute encoder, or scale). As the motor rotates, the encoder sends pulses. The control identifies a specific pulse as the "Grid Point" – a reproducible position for machine zero.

The machine cuts perfect straight lines but oval arcs. This is often a mismatch between 1860 and the acceleration for the orthogonal axes. Ensure that the 1860 values for X and Y (or X and Z) are identical for circular moves. Uneven acceleration distorts circles into ellipses.

. This value represents the amount of shift required to align the absolute encoder's internal reading with the machine's actual reference position. Key Functions & Characteristics

If Parameter 1860 is set to 0 , the machine does not apply a specific clamp speed during deceleration/acceleration transitions. This allows the machine to use the full time constant defined in other parameters, resulting in smoother motion but potentially longer cycle times.