So I am coming from the 3D printing world where it is very common to use Gcode to probe the bed in many places and use those values to compensate the z axis. I have been cutting some 6mm aluminum sheets and they aren't always perfectly flat even after multiple securing points. I am have searched the wild lands of google and these forums and I don't really see anyone talking about it much? Is there a way to achieve this with a Lua macro of some kind relatively simply? Thanks, from a very new guy to CNCs.

Hi,
there are two ways that I know of.

I use Autoleveller, a freeware program that generates a Gcode probing routine from your original Gcode file,
then probes the substrate, then corrects the original Gcode file to accommodate the substrate not being perfectly flat.
I've been using it for years making PCBs which are very sensitive to Z axis engraving/cutting height.

The other is the mcSurface wizard of Mach4. It will probe an area according to your definition and then automatically
adjust ALL z axis ordinates thereafter, on the fly, without recomposing or otherwise editing the Gcode.

Both achieve the same result. Autoleveller is a clear and transparent process that is used again and again as required. mcSurface
is more intended that the baseboard of the router be probed and thereafter all corrections happen within Machs core and not
really subject to your control. It was always intended as a 'probe once and forget' type solution whereas Autoleveller is a
'probe each workpiece and modify the Gcode to suit' solution.

Either will work.

Craig

There is a video on the surface wizard on the Mach Support youtube channel

https://www.youtube.com/watch?v=M4o6dfQrAo8