References: Fanuc 0i-D, 0i-F, 31i-B5 Series Connection Manual (B-64643EN) and Parameter Manual (B-64640EN). Always consult your specific machine tool builder's documentation as they may override standard Fanuc recommendations with custom PMC logic or secondary parameters.
A common mistake made by technicians attempting to shift an axis home position (e.g., trying to adjust a Z-axis tool change height) is typing a new number directly into Parameter 1860.
Understanding Fanuc Parameter 1860: Absolute Position Detection
When troubleshooting absolute position issues, you will likely need to check these associated parameters: 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.
When the absolute pulse coder battery dies completely while the machine is unpowered, the internal encoder count resets to zero. Upon restart, the system flags a synchronization alarm because the physical state of the axis no longer correlates with the reference string stored inside Parameter 1860. 2. Physical Axis Crash or Disconnection
When setting parameter 1860, users should consider factors such as: Upon restart, the system flags a synchronization alarm
: When a grid shift or homing operation is initiated (using the APZ bit in Parameter 1815), the CNC system reads the exact physical location of the motor's rotor relative to the scale or grid marker.
During rapid positioning, axes accelerate and decelerate at their maximum capabilities. Due to inertia, friction, and the physics of mass in motion, a small amount of lag is normal. However, if the lag becomes too large, it indicates a severe problem.
| Machine Type | Rigidity | Typical 1860 Range (ms) | | :--- | :--- | :--- | | Small VMC (BT30) | High | 30–60 | | Large VMC (BT40/BT50) | Medium | 60–120 | | Heavy-duty lathe (X-axis) | Medium | 80–150 | | Gantry mill (heavy slide) | Low | 120–250 | | High-speed machining center | Very High | 10–40 | During rapid positioning
: 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
: Governs rotation axis behavior alongside parameter 1861. When PRM 1815 bit 6 (NRT) is configured, passing the threshold in parameter 1860 commands the system to update or round the reference position data relative to the 360-degree or parameter 1260 coordinate limits. Technical Specifications
The relationship between time constant (T) and acceleration (a) is: