Material Thickness

The material thickness seems not working.
When device setting is not on relative mode, the gcode it generated use relative position.
Following is part of save gcode:

G0 X121 Y312.79 F2000
G91 ← set to relative position
; Scan @ 799.998 mm/min, 25% power
M106 P0 S255
G0 X0 Y-26.8 F2000
G0 Z7 ← isn’t it should be absolute position?

The relative move mode is set. I didn’t see any Z move on the gcode.

I don’t believe that disabling “Relative Z moves only” implies that only G90 commands will be used. Similarly, if you use Absolute Coords for your coordinate system LightBurn will still use G91 for jobs depending on circumstances.

Did the end position for the Z height still end up where expected? Or are you posting because material height is not working as you expect?

If so, can you describe the specific circumstances of what you’re seeing?

I’m not sure where to set the focus length.
This is how I setup.
Z0=focal length.
If I put material thickness of 7mm, it will advance to Z7 which is correct.
If I re-run the job since it is relative positiion, Z will be Z14. This is not what it should be.
It should be Z7 since material thickness still 7mm.

Can you upload a screenshot of your Device Settings and the .lbrn file that you’re using to test?

This is the code I get for a simple 100x100 mm square line cut with material height set to 7 mm:

; LightBurn 1.1.03
; GRBL device profile, absolute coords
; Bounds: X100 Y100 to X200 Y200
G00 G17 G40 G21 G54
; Cut @ 6000 mm/min, 20% power
G0 X100Y100
G0 Z7
; Layer C00
G1 Y200S200F6000
G1 X200
G1 Y100
G1 X100
G1 S0
; return to user-defined finish pos
G0 X0 Y0

You can see that it’s using absolute moves and goes to 7mm Z appropriately. I would expect it to go back to starting position but maybe that makes sense. Not sure.

This was done with Absolute Coords. I noticed that if I use Current Position it uses relative moves but does go back to starting point.

The “Absolute coords” works.
The “User Origin” is relative mode.
The “Current Position” is relative mode.

I guest that is how it is design.
The coordinate system "Start from " has some design that is not what I expected.

So where to put the focus distance on LB?