I did modify my 7W laser engraver complete from the original Chinese laser engraver. U replaced the board for grbl 1.1 with control for 3 axis. Then I added the Z axis. I install limit switches for all X, Y and Z. So far so good everything works. When I home Z i do that in the upper part since I think is safer due I won’t damage my laser against the bed if something goes wrong.
My problem is:
When I home Z, the laser focal length, is too far from the surface of the material I want to cut/engrave. so I want to move Z down 40 mm (this will give me a focal length of 7.5 mm), to have it focus to the bed surface at that position, then I want to offset the material thickness so I can cut thicker materials. these are some of my setting in Light-burn. I have try pretty much all from the setting but not able to do so. Please any help will be much appreciated.