APC Alarm: Need Zero Return.
There is a known technical note regarding FANUC 0i-MC/MD models. Contrary to the absolute encoder definition, the parameter manual for these specific series sometimes defines Parameter 1860 differently. In the context of servo tuning, it is labeled as the "First acceleration for Two-Stage Backlash Acc. function" .
Parameter 1860 cannot be looked at in isolation. It relies on a cluster of coordinate, encoder, and feedback parameters to properly govern an axis. Related Parameter System Function Operational Link to 1860 Position Detector Settings ( APC , APZ )
In the vast majority of FANUC controls, specifically those using for axis positioning, Parameter 1860 serves a vital purpose. It stores the first part of the reference position data for an absolute encoder. You will rarely, if ever, type a number directly into this parameter. Instead, the CNC writes to it automatically. fanuc parameter 1860 full
Known as BLEN , this bit must be set to 1 to enable backlash acceleration functions. Commonly Confused Parameter: 1815
The following is a general procedure for re-establishing the absolute reference position using Parameters 1815 and 1860/1861:
After rebooting, set PARAMETER WRITE back to 0 and press RESET to clear the alarm. Pro-Tip: The Grid Shift Limit APC Alarm: Need Zero Return
| Parameter | Function | |-----------|----------| | 1850 | Grid shift amount (reference position fine offset) | | 1851 | Reference position coarse shift | | 1820 | Number of pulses per motor rotation / detection unit | | 1420 | Rapid traverse speed | | 1421 | FL speed (deceleration speed for ZRN) | | 3003 (bit 5) | ZRN direction selection |
By following this guide, you can confidently adjust Fanuc Parameter 1860, recover from a lost zero, and keep your CNC machining center running with original factory precision. Remember: The parameter itself never crashes the machine – only the incorrect value typed by the user does. When in doubt, revert to zero and call a professional.
Suppose your Z-axis zero is currently 5.000 mm too far toward the spindle (meaning the tool would crash). You need to shift zero positive by 5.000 mm . In the context of servo tuning, it is
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.
Whether the axis uses a or just the motor encoder Any alarm codes currently showing on the screen Share public link