Common CNC Machine Parameter Guide

1. Handwheel pulse generator failure

A FANUC 0TD CNC lathe experienced a failure of the handwheel pulse generator, preventing fine tool offset adjustments. Replace or repair the faulty unit. If no suitable spare is available, temporarily set parameter 900#3 to 0 to disable the handwheel pulse generator and use the jog button single-pulse function for fine tool adjustment. After the handwheel pulse generator is repaired, restore the parameter to 1.

2. Overtravel alarm during homing

During homing the machine displayed a 510 or 511 overtravel alarm. Two remediation methods:

1. If the X axis triggers a 510 or 511 overtravel alarm during homing, change parameter 0700LT1X1 to +99999999 (or change 0704LT1X2 to -99999999), then perform homing again. If homing completes successfully, restore the original value of parameter 0700 or 0704.
2. Power on while holding P and CAN simultaneously to clear the overtravel alarm.

3. ALM701 alarm shortly after power-on

A FANUC 0i lathe raised ALM701 shortly after startup. The maintenance manual indicates this alarm signals overheating of the control unit upper fan. Open the electrical cabinet and check the fan motor; if the fan does not run while fan power is present, the fan is likely defective. If a replacement fan is not immediately available, set parameter RRM8901#0 to 1 to release the ALM701 alarm, then apply forced air cooling. After a replacement fan is obtained, set PRM8901 back to 0.

4. Common maintenance parameters

1. ALM701: System fan detection fault. Set 8109#0=1 to mask this alarm.
2. Setting absolute encoder: parameters 1815#4 and 1815#5. To configure an encoder as absolute, set 1815#5=1, move the axis to the zero position, then set 1815#4=1. If the setting fails, move the axis a short distance away and back to the origin, then retry.
3. Convert full closed-loop to half closed-loop: set 1815#1 to 0 to switch to half closed-loop. Then adjust parameters 2084 and 2085 according to the ball screw pitch.
4. Lock the SYSTEM key: in the SETTING screen set parameter 3208#1=1.
5. Soft overtravel alarm: alarm numbers 500 or 501. Set parameters 1320 or 1321 to 9999999 and -99999999 to suppress the alarm. After clearing, return the machine to origin and re-enter the original parameter values. This fault often occurs after replacing a ball screw, motor, or re-entering parameters.
6. Machine interlock signal: refer to parameter 3003 to determine causes for a locked machine that will not move.
7. Chinese display: 3102#3=1
8. Servo adjustment screen display: 3111#0=1; Spindle monitor screen: 3111#1=1; Operator monitor: 3111#5
9. Spindle positioning: 4077, used to adjust spindle tool-change position.
10. No-homing operation: if the machine can run in automatic mode without homing, set 1005#0=1.
11. Macro program protection: disable macro program protection with 3202#0=0 (program numbers 8000–8999); 3202#4=0 (program numbers 9000–9999).
12. Mask serial spindle: sometimes required during maintenance to isolate the serial spindle, set 3701#1=1.