Best approach to multi day carves?

Im currently carving a topographic side table. Its going to have to be done over two days. What is the best method to ensure the x and y registration remains the same between days?

If i turn the machine off i know from experience that it would not align perfectly like if i did step two of my carve directly after step one.

Is the only real way to ensure things continue smoothly to leave the machine on and my laptop attached? If i disconnect the laptop it will ask me to home the machine on reconnect which i believe also affects the x/y?

Am i missing something really simple (its totally possible)

If I understand you correctly.
You need to look at why homing does not give exact consistent positioning.
That indicates a mechanical problem with machine.

Introduce a known reference point, either switches or something you can calibrate up against.

Actually, if you have some extra t-slot nuts, I have put them in on both my x and y axis, extra ones so when I set zero on a board that I know will require multiple bit changes and long carves, perhaps, additional days, I set the x and y 0 with the nuts and some screws up against the x and y gantries. Tighten the nuts and then before applying power to the machine for the next carve after changing bits, etc, I move the x and y gantries up against the screws that were tightened up at x0, y0.

Works every time, then power up the machine and start with the next carve.

Actually, you can use the previous X,Y zero after turning off the machine

Correct, but a fixed reference point is required to zero the machine off of.

With homing switches installed the 2nd day procedure will be as follows:

  • Perform a homing cycle (establishing machine zero)
  • Carve, using previous Home Position aka work zero.
    If a new bit haven been inserted you need to re-establish Z zero.