You can install homing switches, this is probably your best bet, but it takes some doing obviously.
If it’s not critical, you can power off the machine and power it on again later without touching it. There is a real chance your cutting head will slightly move upon powering up. That’s why I said: do this only between operations that aren’t critically positioned relative to each other. For example, vcarve a sign - power down - power up - do the profile cut. Your vcarve might me half a millimeter off centre relative to the cutout because of this, but who’ll notice that…
Even so, there’s an important order of things you need to do for this to succeed.
- Make the gcode in 2 separate files. There are means to resume within a gcode file, but that’s another story.
- After the first part, before powering down, send your cutter back to home!
- When powering up, it will take its current coordinate as zero. That’s why you must home before powering off.
- Start the second cut.
If I left something out or misspoke, someone hopefully will chime in.