Zero Return in FANUC CNC machines is essential to creating an accurate reference point and must be performed whenever using an absolute position encoder, otherwise home positions must be manually reset manually. Below is a step-by-step guide on how to accurately set the zero return position.

Manually move the machine to the home position, set parameter 1815 #4 = 1, shut down the machine and restart with power off, that is to determine the current point as the home position.

If 1815 #4 cannot be set to 1

1. Ensure that the Motor rotates at least one revolution or more
2. Set parameter 1815#5=0, 1815#4=1, 1815#5=1, power off and restart.
If 1815#5 APCx = 1, use absolute position encoder
If 1815#5 APCx = 0, use relative position encoder
If 1815#4 APZx = 1, the absolute encoder zero return is successfully set.
If 1815#4 APZx = 0, absolute position encoder home position is not set. (Alarm 300 will be generated)
If 1815#1 OPTX = 1, Full closed-loop mode enabled..
If 1815#1 OPTX = 0, Semi-closed-loop mode enabled.
For best results when using an absolute position detector, the initial adjustment or when replacing one must be set to 0, with home position later set manually back to reference point or other operations when power returns on after restart. When position correspondence between mechanical position and absolute position detector is achieved, this parameter will automatically set back to 1.