TLDR: The ‘unexplained’ G code was the laser offset plus the overscan. The other issues where stemming from the outline move not corresponding to the content area actually lasered and the fact that the ‘absolute coord system’ described in the docs to not actually mean the machine coordinate system (as it is hinted at in the docs) but relative to the snapmaker work origin if set.
Thanks to everybody who chimed in
Maybe we are getting somewhere and I do appreciate your time. What makes you say the file is using Absolute Coordinates ? Where is that setting ? In the documentation it says the “Laser Window” has the Job Origin and Start From areas to pick that. And those are set to “current position” though i tried them all and could not see a difference yet.
The ‘home’ position on the snapmaker is quite far back on the left and of course it moves there on startup. That is what snapmaker calls home at least.
But its an irrelevant position. Before starting the job you have to level the height and set a work origin, which I always do.
The “Work Origin” (Snapmaker term) is a specific place on the target surface where I want the “origin” of lightburn to be. So I position the positioning laser exactly at that point.
Absolute coordinates as described in lightburn docs are based on the machine absolute coordinate system. But that would mean a totally different position and i cannot reliably or easily position my target with respect to that position.
What do you mean a simple raster fill layer. I tried a simple square fill before start of thread and it made no difference other than it moving less in the wrong direction.
The Preview window shows the movements I would have expected from the perspective of the origin.
- After comparing the output with Luban i see it uses Absolute G90.
- After generating a number of NC files I see:
- User Origin adds a G90 (absolute) G0 X0 Y0 command which should move it to machine 0/0. BUT Snapmaker documentation says G90 will change to ‘logical’ coordinate space.
- After more testing Snapmaker uses G92 X0 Y0 to set the ‘work origin’ which means the ‘absolute’ coordinate system used after that moment is NOT the machine coordinate system as described in Coordinates & Origin - LightBurn Documentation (lightburnsoftware.com)
4.I imported a new NC file with absolute origin and it seems to work alright, BUT the “run boundary” command gives a totally wrong area. That means some of my earlier statements (which where based on run boundary) where wrong. See Run Boundary on lightburn generated gcode twice as large - Snapmaker 2.0 - Snapmaker: where creation happens
Can i get Lightburn to create G90 commands instead of G91 ? EDIT: Yes with “Current Position Mode”