ZMAX home, probe work coordinates

[Darwin (Darwin McGrath)]

@jamiek and I just had a chat related to G38.2 if this is of any help:

Is there a way to make G28 not change G53 coordinates? Or an alternative?

So… I’ve got a z touch plate working but it was a surprise to me that it sets the machine coordinates to z0 when the touch plate is triggered by a G28 command. Of course it does! These are the commands recommended for the tiny touch plate: G28 Z G92 Z0.5 G0 Z5 F480 I thought G28 positioned the tool tip at the trigger point and you had to issue a command like G92 Z0.5 to set Z in your workspace (I use G54). What actually happens is G28 Z moves the bit to the z endstop (the touchplate in t…

FWIW these are my probing commands.
Z-57 is the surface of my spoilboard in machine coordinates given I always turn the machine on with the gantry in the same location, and I run G38.2 in machine space, not workpiece space. Z is always set to 0 by G38.2 in workpiece space so my Z0 in machine space is unchanged. My touch plate is 7.9mm thick:

G53 G38.2 Z-57 ; Probe Z in machine space
G92 Z7.9 ; Set current offset to 7.9mm for Z to account for touch plate thickness
G0 Z20 F480 ; back up to an ultra safe distance