| Bit | Axis (Typical) | Function when = 1 | Function when = 0 | |-----|----------------|-------------------|-------------------| | 0 | 1st axis (X) | Release interlock | Remain interlocked | | 1 | 2nd axis (Y) | Release interlock | Remain interlocked | | 2 | 3rd axis (Z) | Release interlock | Remain interlocked | | 3 | 4th axis (A/B) | Release interlock | Remain interlocked | | 4 | 5th axis | Release interlock | Remain interlocked | | 5 | 6th axis | Release interlock | Remain interlocked | | 6 | 7th axis | Release interlock | Remain interlocked | | 7 | 8th axis | Release interlock | Remain interlocked |
The CNC will monitor the fan speed. If the fan fails or its RPM drops below a threshold, the system triggers a 701 alarm and may inhibit operation to prevent overheating. Why Technicians Use It This parameter is typically used as a temporary bypass rather than a permanent solution: Troubleshooting:
After hundreds of service calls, experienced FANUC technicians have learned hard-earned lessons about Parameter 8901. fanuc parameter 8901
This is the most frequently accessed bit. It controls the detection of the control unit’s upper cooling fan.
: 8901 = 00000111 binary → Bits 0,1,2 = 1 → Axes X, Y, Z are released from interlock. Axes 4+ remain locked. | Bit | Axis (Typical) | Function when
To change this parameter, the machine must be in MDI Mode or Emergency Stop state with "Parameter Write Enable" (PWE) set to 1.
⚠️ Releasing interlock overrides protective functions (e.g., door-open motion lock). Always ensure that P8901 is set to release only the axes necessary for safe setup or maintenance. Never release all axes (e.g., 255 decimal) without risk assessment. This is the most frequently accessed bit
If you have a dual-spindle lathe (main and sub-spindle), remember Parameter 8901 affects Spindle 1. Parameter 8902 affects Spindle 2 (if equipped). Changing the wrong one will do nothing—or cause chaos.
Setting parameter 8901 requires a good understanding of your CNC machine's control system and the specific requirements of your machine. Here are the general steps to follow:
Fan monitoring is Disabled (Shielded) . This clears the 701 alarm and allows the CNC to run without a functioning internal fan.
Modifying parameters without understanding the consequences can crash a tool changer, break a tool, or damage the spindle. Follow this step-by-step guide precisely.