Skew when scanning

[ciccio2a (BS)]

Hello, here is my issue :
I assembled a laser with 3d printed parts and with a lasertree module.

When in line mode or offset fill everything is working ok.

In scanning mode I have an alternating skew (see photos) .
It’s really visiblke when looking at the zero or the border of the gradient

Any ideas?

I tried with and without overscan, I tried checking my belts and pullies, everything is snug, i have no further ideas.

Thanks for your help !

[berainlb (PY)]

Run a bi-directional fill on a rectangle and set line interval to something like 1 mm. If the results show different start and end positions for either direction then this is a scanning offset issue.

This can be either mechanical or electronic in nature.

If mechanical this is created by backlash in the system. Check everything but especially your X-axis pulley that it’s properly secured to the stepper motor. Create a circle design and run it. Do the ends of the circle meet perfectly? If so, then the problem is likely electronic.

You can use “Scanning offset adjustment” in Edit->Device Settings to address an electronic issue.

More information here:
Scanning Offset Adjustment - LightBurn Software Documentation

[ciccio2a (BS)]

Thanks i’m gonna do that right now, then in will post the results here:
update :
As you can see in the pictures there is a difference in start and end postion as you predicted.
And the circle seem perfect.
I’m gonna try what you recommended in the documentation and i’ll update the post. Thanks !