a) How do they probably do it on my "store bought" milling machine? No need to home it. The beast knows where it is after it is powered on.
Absolute encoders.
b) Can the home position be defined in the center of the machine travel? That would make the request easy. The axis can be homed at the position that was reached and the G54 can be "touched off".
Yes, even with normal encoder or without them, must have home switches.
It will home normally at axis ends, and move to wherever you would like it to be home.
c) Can the machine be homed normally, then after disabling the motors moving it around and keep track of the position? Provided some feedback is available e.g. rotary encoder on the hand wheel, or linear encoders?
(that would allow to use the Linux similar to a normal DRO, when the motors are disabled.)
This kind of tracking without motors might be also interesting to teach a machine.
Yes, all that can be done.
Teaching should also be possible without encoders, jogging the machine to required positions and saving coordinates.
