What determines home position?
The CNC Controller is a software Program called Mach 3 and provides for controlling all the movements and associated commands. The CNC controller (Mach) does not know a "practical" Machine Reference Point to work from, thus, the controllers “0,0,0” is somewhat meaningless and has unlimited movement capability. When the controller is turned on it monitors axis movement starting from Mach's “0,0,0” value for each axis and displays the absolute movement using Machine Coordinates.
Machine Zero is a fixed point within the physical machine travel limits and does not normally change. It is typically called Machine Reference point, machine zero, or simply "Home" Position. Machine zero can be located / defined anywhere by the user. Usually it is located to provide for full available machine travel usage.
Now knowing the above ......How do "YOU" want to tell the controller where home is?
RICH