Fanuc Parameter 1860 (often referred to as P1860) is a critical setting used to define the Position Deviation Limit (Position Error) during a stop or at rest. It essentially sets the "allowable window" for how far an axis can drift from its commanded position before the CNC triggers a Servo Alarm (typically SV0410). 1. Purpose of Parameter 1860
When a machine tool axis is stationary, it is still under servo control. External forces—like gravity on a vertical axis or heavy cutting loads—can try to "push" the axis away from its target position.
The Guardrail: Parameter 1860 tells the CNC: "If the axis moves more than
amount while it's supposed to be stopped, shut the machine down for safety."
The Alarm: If the deviation exceeds the value in 1860, the system generates SV0410 SPECIFIED STOP EXCESS ERROR. 2. Standard Values and Units The value in Parameter 1860 is set in Detection Units. In most standard metric systems, 1 detection unit = In most standard inch systems, 1 detection unit =
Typical Default Setting:Most manufacturers set this between 20 and 100 (
). If the value is too small, the machine will "nuisance trip" on minor vibrations. If it is too large, the machine might allow dangerous mechanical drift before stopping. 3. Comparison: 1860 vs. 1828 It is common to confuse Parameter 1860 with Parameter 1828.
P1828 (Moving): Defines the allowable error while the axis is in motion. This is usually a large value (e.g., 5000+ units) because lag is expected during high-speed movement.
P1860 (Stopped): Defines the allowable error while the axis is stationary. This is a much tighter value to ensure precision and safety. 4. Troubleshooting SV0410 Alarms
If you are getting a Stop Excess Error and your Parameter 1860 is set to a standard value, the problem is likely mechanical or electrical, not the parameter itself:
Gravity Sag: On vertical (Z) axes, the brake might be slipping or the counterbalance (if equipped) might be failing, causing the axis to drop slightly when the motor stops.
Tight Ways/Gibs: If the axis is physically "stuck" or binding, the motor might struggle to settle into the final position window.
Servo Tuning: If the Position Gain (P1825) is too low, the axis won't have enough "stiffness" to stay in place. fanuc parameter 1860 full
External Force: A heavy part or a misaligned fixture pushing against the tool can cause enough deflection to exceed the P1860 limit. 5. How to Modify Parameter 1860 Set the machine to MDI Mode.
Press the [SETTING] function key and change Parameter Write Enable (PWE) to 1. Press the [SYSTEM] key, then the [PARAMETER] softkey. Type 1860 and press [NO. SRH]. Locate the axis you wish to change (X, Y, Z, etc.). Input the new value and press [INPUT].
Change PWE back to 0 and press [RESET] to clear the resulting PWE alarm.
Caution: Never set Parameter 1860 to 0 or an extremely high value as a "fix" for a mechanical problem. This disables a vital safety check and can lead to machine crashes or damage to the ball screws.
Technicians often confuse 1860 with other parameters. Here is a clear comparison:
| Parameter | Function | When Active | Typical Range | | :--- | :--- | :--- | :--- | | 1860 | 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) |
Critical Insight: Parameter 1860 and Parameter 1825 (position loop gain) work in tandem. If you increase 1825 for higher stiffness, you may need to decrease 1860 to avoid instability. Conversely, a low 1825 with a very low 1860 will cause overshoot.
| Feature | Detail | |---------|--------| | Parameter # | 1860 (axis 1), 1861 (axis 2), … | | Purpose | Final approach speed for G28 reference return | | Units | mm/min (metric) or 0.1 inch/min (inch) | | Typical range | 500 – 6000 mm/min | | Key constraint | Must be ≤ parameter 1420 (Rapid) | | Failure mode if too high | Missed reference signal → alarm or position drift | | Failure mode if too low | Long cycle time, but safe |
In FANUC control systems, Parameter 1860 is specifically used to define the current position of an axis when using an Absolute Position Detector
. This parameter is part of the axis-specific settings (1800-series) and is critical for maintaining machine coordinates without needing a reference return (homing) every time the power is cycled. Key Function & Usage
: It stores the absolute position data for each controlled axis. Absolute Encoders : This parameter works in conjunction with Parameter 1815 (specifically the
bits), which tells the system that an absolute pulse coder is being used and whether the reference position has been established. Coordinate Synchronization Fanuc Parameter 1860 (often referred to as P1860
: When the machine is powered on, the CNC reads the value from the absolute encoder and reconciles it with the value stored in Parameter 1860 to determine the exact machine position. Common Technical Scenarios Battery Failure
: If the backup battery for the absolute pulse coder dies, the data in Parameter 1860 may become invalid. This often results in a 300-series alarm (e.g., APC Alarm: Reference Return Required).
: A common error associated with this parameter is "Alarm 309: Reference Return Impossible," which typically occurs if you attempt to set the reference position (APZ bit in 1815) before the system has properly recognized the encoder data or if there is a mismatch with Parameter 1860. Homing After Battery Swap
: After replacing batteries, you must typically move the axis to the physical home position and toggle Parameter 1815 (APZ) to "1" to update Parameter 1860 with the new zero-point data. How to Modify (If Required) To change axis parameters like 1860, you must first enable Parameter Write Enable (PWE) [OFFSET SETTING] PARAMETER WRITE and change the value to
The control will issue a "100 PARAMETER WRITE ENABLED" alarm; this is normal. Navigate to [PARAMETER] , and press to find the specific axis values.
Incorrectly modifying Parameter 1860 can cause the machine to "lose" its position, potentially leading to crashes if the software limits no longer align with the physical machine limits. Are you currently dealing with a specific alarm code (like 300 or 309) after a battery change? How to Enable Parameter Write Enable (PWE) on a Fanuc CNC
Understanding FANUC Parameter 1860: A Comprehensive Guide
FANUC, a renowned Japanese company, is a leading manufacturer of industrial robots, CNC machines, and other automation solutions. In the realm of CNC machining, FANUC's control systems are widely used for their precision, reliability, and flexibility. One crucial aspect of FANUC's control systems is the parameter setting, which allows users to customize and optimize the machine's performance. In this article, we will delve into the specifics of FANUC parameter 1860, exploring its significance, functions, and configuration.
What is FANUC Parameter 1860?
FANUC parameter 1860 is a specific setting within the FANUC control system that relates to the machine's operation and performance. This parameter is part of a larger system of parameters that allow users to customize and fine-tune the CNC machine's behavior. Parameter 1860, in particular, is associated with the "High-speed machining" or "Advanced preview" function.
Function of FANUC Parameter 1860
The primary function of parameter 1860 is to control the advanced preview function, which enables the CNC machine to predict and optimize the machining process. This feature allows the machine to: Parameter 1860 vs
By fine-tuning parameter 1860, users can optimize the advanced preview function to suit specific machining requirements, such as:
Configuration of FANUC Parameter 1860
The configuration of parameter 1860 involves setting a specific value that determines the level of advanced preview and optimization. The value range for this parameter varies depending on the FANUC control system version and the specific machine model.
Typically, parameter 1860 is set to a value between 0 and 100, where:
When setting parameter 1860, users should consider factors such as:
Best Practices for Setting FANUC Parameter 1860
To maximize the benefits of parameter 1860, follow these best practices:
Common Issues and Troubleshooting
If issues arise after setting parameter 1860, consider the following:
By understanding and effectively utilizing FANUC parameter 1860, CNC machine users can unlock the full potential of their machines, achieving improved machining performance, reduced cycle times, and enhanced productivity.
Important safety notes:
How to confirm exact definition for your controller:
If you tell me your exact Fanuc control model and software version (for example "Fanuc 0i-MF v9.07" or "Fanuc 21i-TB"), I will give the exact definition and permitted values for parameter 1860.
If the absolute encoder battery dies, the machine loses its zero position. After replacing the battery, you must re-establish machine zero. Parameter 1860 allows you to "tell" the control where the new zero is relative to the mechanical hard stops.
