Offset burn artifact at higher power / lower speed

[tnfwoodwork (Josh)]

I’ve been running material test grids on red oak and noticed a consistent artifact — a darker burn area that appears offset slightly down and to the left of the intended cell boundary. It shows up at higher power settings (60%+) across multiple speed ranges, and becomes more pronounced at speeds slower than 200mm/s (175mm/s and 150 mm/s). It’s present on all three test grids I ran today.

This zoomed in image is at 150mm/s, 75%, 0.10mm line interval.

I’m running an OMTech MF2028 80W CO2 with the most recent update of Lightburn on Windows.

Is this a mirror alignment issue? A scanning offset? Or something mechanical like a backlash? And is it likely to affect quality on a real project at these settings?

[bernd.dk (Bernd)]

@tnfwoodwork

A scanning offset?

It is possible that there are several things that are not optimal, but one of the things could be your scanning offset.
To find out, you need to do a test with a slightly higher line spacing, e.g. 0.2mm on cardboard or other light material, then you will see the effect better like in my example.

If you have something like this:

then you should/can adjust this. (on the sides of the block)

But a good inspection of the machine’s moving parts as well as the mirrors and the lens will also be part of this investigation.
Correct alignment and focus are always the basic prerequisite for your machine to deliver satisfactorily.