Using Z offset with an auto focus CO2 machine

I have an OMTech AF-2028-80 (has autofocus).
I want to have the FILL layer automatically go out of focus by 3mm (by raising laser head 3mm), but then return to normal focus after the fill for my LINE layer.
Would I use the Z OFFSET setting under the FILL layer to do this? (Since it is in INCHES, I would have to convert the 3mm to inches)… and if so, would a POSITIVE number make the laser head go UP or down?

Yes, Zaxis travel is always positive=up and negative=down.

I do not have a motorized Zaxis, so I cannot answer the other question.

That’s true for CNC machines with moving spindles & heads.

For lasers (and 3D printers) that move the platform under a fixed head, think of it this way:

  • +Z = increases the distance between the head and the platform by moving the platform down
  • -Z = decreases the distance between the head and the platform by moving the platform up

Except, of course, for machines treading their own path through the wilderness of GRBL forks, wherein anything is possible, nothing is standard, and the jank is strong.

Trust, but verify.

1 Like

Thanks guys!
I actually stated it wrong… LOWERING the bed is the same as RAISING the laser head. The AF moves the bed up and down, not the laser head. But I know you guys know that!
I experimented with that today and found that negative number lowers the bed.
And since the Z Offset on the LINE part was set to 0, it raised the bed back up to put it back in focus for the cut.
I’ve been using Lightburn for almost 2 years now, and never messed with that setting But WOW… it makes a huge difference in the quality and darkness of the engraved letters! I should have been doing this since the beginning!