Let's brainstorm together to find solution

[EliasPolitis]

Under normal circumstances, this is true. Unless you use G92, your Z should be persistent.

I can think of a few exceptions:

• bit shifted inside collet (collet nut not tight)
• router shifted inside mount (mount not tight)
• workpiece shifted up (possible with side clamping e.g. cam style)
• X axis tilted up about the side plates (possible in a Z crash)

.5" is hard to imagine though. It would make me suspicious of lost steps.

EDIT:
Which reminded me of this.

[SOLVED] Z shifting after 1000s of moves on X-Controller

Ok, here’s a tricky one… I tried cutting 4 simple circular pockets and used jscut’s ramping feature (i.e. instead of straight plunging, it ramps into the required Z - or creates helical movements in my case of circular pockets, to optimize tool life). The outcome is ~9k lines of gcode, half of which involve Z moves. In the end of running the gcode, I noticed that it went back to the given safe height of 3mm (Z WPos showing indeed 3), but it was actually about twice higher. Here’…

This was a very weird situation. I once experimented with 2:1 gearing and 1:1 ustepping on the Z (as opposed to 1:1 gearing and 1:2 ustepping) and experienced consistently lost steps that were consistently affected based on acceleration and junction deviation values.