Fanuc parameter position error limit when the axis is stopped
This parameter defines the maximum allowable deviation (in detection units) between the commanded position and the actual position while the machine is at a standstill. If the axis drifts or is pushed beyond this limit, the system triggers a Servo Alarm 410 (Excessive Position Error). Key Details & Troubleshooting
It acts as a safety monitor for when the machine is supposed to be stationary. Common Alarm: typically occurs if this limit is exceeded. Potential Causes of Error: Mechanical Load:
Something is physically pushing the axis out of position (e.g., gravity on a vertical axis without a proper brake or counterbalance). Inertia/Braking:
The axis cannot stop fast enough due to a time constant that is too short for the current feedrate. Mechanical Wear:
Issues with lubrication or a faulty ball screw can cause the axis to "jump" or settle poorly, exceeding the limit. Typical Resolution:
While increasing the value in parameter 1829 can stop the alarm, technicians recommend checking for mechanical problems cable issues first to ensure the machine remains accurate. How to Modify To change this value, you must typically: Navigate to the screen and enable PARAMETER WRITE (PWE) Search for fanuc parameter 1829
and enter the new value for the specific axis (X, Y, Z, etc.). Disable PWE and reset the CNC to clear the alarm. FANUC 410 Servo Alarm - CNC Machining - Practical Machinist
Understanding FANUC Parameter 1829: The "Excess Error" Guard If your CNC machine has ever ground to a halt with a 410 Servo Alarm , you've likely encountered FANUC Parameter 1829
. Often referred to as the "Excess Error (Stop)" limit, this parameter is a critical safety threshold that prevents your machine from crashing or damaging its own servo motors when something goes wrong while at a standstill What is Parameter 1829? Parameter 1829 defines the
allowable positional deviation (error) while the axis is stopped
In a closed-loop CNC system, the controller constantly compares where the axis be with where the encoder says it
is. Even when "stopped," the motor is actively holding its position. If an external force (like a heavy tool or a mechanical bind) pushes the axis out of place by more than the value set in 1829, the system triggers an alarm to protect the hardware Why the Alarm Triggers Fanuc parameter position error limit when the axis
When the deviation exceeds the 1829 limit, you'll typically see a 410 Servo Alarm . Common causes include: Mechanical Obstructions:
Physical binds, packed chip buildup, or a lack of lubrication in the ballscrews Worn Components:
Excessive friction from worn ways or bearings that the motor can't overcome to maintain position Servo Tuning Issues:
If the servo gain is too low, the motor might "drift" too far from its target position. Troubleshooting and Adjustments
While it is tempting to simply increase the value in Parameter 1829 to "clear" the alarm, this often masks a deeper mechanical issue . Follow these steps instead: Check for Binds:
Manually inspect the axis for physical obstructions or chips Verify Lubrication: How to view/change safely
Ensure the automatic lubrication system is functioning and that the ways aren't dry Monitor Position Deviation: Use the CNC's Diagnosis Screen
(often DGN 300 or similar) to watch the "error" or "position deviation" in real-time. If it sits near the 1829 limit while idle, a mechanical problem is likely Enabling Changes: If you must adjust the parameter, you will need to enable Parameter Write Enable (PWE) Setting screen Key Related Parameters Parameter 1828: Defines the allowable error while the axis is (interpolating). Parameter 1826:
Defines the "In-Position" width (used to signal when a move is "finished").
For detailed technical specifications, always refer to your specific control manual, such as the Series 0i-MODEL F Plus Parameter Manual 16i/18i Series Manuals specific steps
to view the current position deviation on your diagnostic screen? FANUC Series 0i-MODEL F Plus PARAMETER MANUAL
Assume a linear axis with a travel range from -100.000 mm to +500.000 mm:
| Parameter | Setting (mm) | Purpose | |-----------|--------------|--------------------------------| | 1320 | -100000 | Negative software limit | | 1321 | +480000 | Positive soft limit 1 (warning)| | 1829 | +500000 | Positive soft limit 2 (final stop) |
Values are stored in detection units (e.g., 1 μm → multiply mm by 1000).