<font face="Arial, Verdana">May be a bug somewhere,</font>
When running from an SD Card, the Set to Origin doesn't change the print off set at all.
The G-code was created the easel program on the inventables site and references the work material as Z=0 on the top.
Engraving is then done into the Z=-x range depending on how deep it has to engrave.
If I set to origin with the z axis at 100mm from the bed then execute the code, the z axis move down to the 0 end stop where the stepper stops (the Z in limit is enabled) but the display shows the negative positions.
Here is the first few lines of the G-Code:
<font face="Arial, Verdana">G21</font>
<font face="Arial, Verdana">G90</font>
<font face="Arial, Verdana">G1 Z3.810 F228.6</font>
<font face="Arial, Verdana">M3 S14000</font>
<font face="Arial, Verdana">G0 X21.034 Y36.741</font>
<font face="Arial, Verdana">G1 Z-1.587 F228.6</font>
<font face="Arial, Verdana">G1 X21.034 Y36.741 F1016.0</font>
<font face="Arial, Verdana">G1 X22.023 Y36.792 F1016.0</font>
<font face="Arial, Verdana">G1 X22.978 Y36.934 F1016.0</font>
<font face="Arial, Verdana">G1 X24.111 Y37.232 F1016.0</font>
I'm still building this so haven't damaged anything yet, not from lake of trying ;-)
FYI the work area available is 750mm x 750mm x 300mm
All axis have both max and min limits and these have been tested.
Next major challenge is setting up a Z-probe, should be fun, then I mount a router to the head :-)