Fanuc Parameter 1860 Full Upd May 2026

Fanuc Parameter 1860 stores the absolute encoder pulse count for each axis, which is crucial for resolving 300 APC alarms caused by lost positional data, often due to dead batteries. Fixing the alarm involves replacing the batteries, setting Parameter 1815 (bit 4) to 1, and re-establishing the physical home position to automatically update Parameter 1860. For detailed instructions, you can read the Practical Machinist discussion and CNCmakers technical support. CNC Fanuc Resetting home position After switching batteries

Understanding Fanuc Parameter 1860: Absolute Position Detection

Fanuc Parameter 1860 (often referred to as APZ) is a critical configuration setting in Fanuc CNC systems (such as the Series 0i, 16i, 18i, and 31i) that indicates whether the reference position for an absolute pulse coder has been established for a specific axis.

When a machine is equipped with absolute encoders, it does not require a manual "home" or zero-return operation every time it is powered on, provided the absolute position is correctly saved. Parameter 1860 is the system's "flag" that tells it whether this position is currently valid. 1. The Core Meaning of Parameter 1860

Parameter 1860 is a bit-type parameter where each bit typically corresponds to a different controlled axis (X, Y, Z, etc.).

0: The reference position is not established. The machine does not know its absolute zero, and you will likely see a "Need ZRN" (Zero Return) alarm or a 300-series absolute pulse coder alarm.

1: The reference position is established. The system knows exactly where the axis is located based on the absolute encoder data. 2. When Does Parameter 1860 Revert to 0? fanuc parameter 1860 full

In a perfectly functioning machine, this parameter stays at "1" indefinitely. However, certain events will force it to "0," requiring a re-homing procedure:

Battery Failure: Absolute encoders rely on a backup battery to "remember" their position when the power is off. If the battery dies, the position is lost.

Encoder Disconnection: Unplugging the encoder cable or replacing the motor/encoder resets the stored position.

Mechanical Overhaul: If you disconnect the motor from the ball screw, the physical relationship between the encoder and the machine zero changes.

Manual Reset: A technician may manually change this bit to "0" to force a new home position calibration. 3. How to Set or Reset Parameter 1860

If you encounter an absolute pulse coder alarm (like Alarm 300), you must re-establish the reference position. Simply typing "1" into Parameter 1860 is usually not enough; the CNC must "see" the machine reach its physical home first. Step-by-Step Recovery Procedure: How to Enable Parameter Write Enable (PWE) on a Fanuc CNC Fanuc Parameter 1860 stores the absolute encoder pulse

The Acceleration Relationship

The relationship between time constant (T) and acceleration (a) is:

a (mm/s²) = Vc / T

Where:

Vc = Cutting feedrate (mm/sec or inch/min – convert to consistent units)
T = Parameter 1860 in seconds (divide ms by 1000)

Example:

Cutting feedrate (F) = 3000 mm/min = 50 mm/sec
Desired acceleration = 0.5 G ≈ 4905 mm/s² (moderate for a small VMC)
Solve for T: T = Vc / a = 50 / 4905 ≈ 0.0102 seconds = 10.2 ms

Real-world adjustment: Most machines will not run a 10 ms 1860 due to mechanical resonance. Multiply by 3–5x for safety (e.g., 40–60 ms).

Parameter 1860 in Special Applications

What is Fanuc Parameter 1860? A Technical Definition

Fanuc Parameter 1860 is a servo parameter that sets the time constant (in milliseconds) for the first-order lag filter applied to the velocity command during cutting feed (G01, G02, G03) operations. Vc = Cutting feedrate (mm/sec or inch/min –

In simpler terms, it tells the servo amplifier how quickly to ramp up the motor’s rotational speed (acceleration) or ramp down (deceleration) when the CNC sends a move command while a cutting tool is engaged with the material.

Difference Between 1850, 1851, and 1860

A common confusion exists among Fanuc parameters. Here is the breakdown:

On many newer Fanuc controls (0i, 31i, 32i), Parameter 1860 is specifically for the absolute position detector reference position.

Professional Recommendations

Never use Parameter 1860 to compensate for tool wear. Use tool offsets (Geometry/Wear).
Keep a printed log of original parameter values inside the electrical cabinet.
Use the "full" range sparingly. Shifting by more than 10 mm suggests a mechanical or setup problem.
For critical applications (aerospace, medical), after changing 1860, run a verification program that checks zero position with a probe or dial indicator.
When in doubt, call Fanuc or your machine builder. A remote service call costs $200; a spindle crash costs $20,000.

Introduction

In the world of CNC machining, precision is everything. A misalignment of just 0.001 inches can scrap a part costing thousands of dollars. Among the hundreds of system parameters that control a Fanuc CNC controller, Parameter 1860 often stands out as both a powerful tool and a potential hazard.

If you have searched for "Fanuc Parameter 1860 full", you are likely trying to understand its purpose, how to set it correctly, or perhaps troubleshooting a machine that has suddenly lost its zero position. This article provides a complete, deep-dive explanation of Parameter 1860 – what it is, how it works, how to calculate the "full" value, and the critical safety steps you must take before editing it.

Calculating the Optimal Value for 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.