Double letters when engraved

I downloaded a new version of Lightburn and now I am having issues with double letters. Before the download, everything was perfectly fine.
Mirrors and lenses are clean and aligned, bed is level. I checked the belt, and I did slightly tighten it, but that didn’t change anything. My cuts are fine.

I have an 80w Omtech,
I did see some others like this question, but non of the answers pertains to my issue, or help me.

Your X axis motion needs to be recheked
See if belt are in tension?

To confirm - if you uncheck bi-directional engraving - does this behaviour stop?

Okay, that fixed the the double but now it’s slanted.
So obviously I need to fix something. How do I go about that. And is that something that all of a sudden just can happen?


I am not expert on CO2 frames
But i am sure someone in the mindhive will give you guidance

Okay, well, thanks for some input.
Does anyone have any insight into what I need to do here?

Sounds like it may be my scan off sets? Something I have never changed. So unsure why this would happen.

This may help with the slanted engraving:

Also, if you had not previously been using the Scanning Offset Adjustment, make sure that it’s (still) turned off:

With those changes settled in place, turn Bi-directional Fill on again and it should work properly. If the edges appear ragged, then make the Scanning Offset measurements again and fill in the table.

Unfortunately, yes. Although it’s rare, updating any program can lead to weird behavior; burning the weirdness into a sheet of wood makes it obvious.

This horror show will help guide you to solutions:

So, what I don’t understand is. In the picture for fixing the of set scan. It shows that the faster the settings the offset changes. Mine doesn’t change. It stays the same from 100mm to 500 mm. They all are 1.5.

That shows there’s mechanical backlash in the X axis, so that the laser head doesn’t move until the motor has turned enough to take up 1.5 mm of slack.

Because this is a big CO₂ laser (right?), look for:

  • A loose belt anchor
  • A loose screw in any of the motor or pulley mounts
  • Anything loose in the laser head: lens, nozzle, the whole thing hanging off the X axis carriage

With the power on (so the machine prevents you from moving the motors), grab the laser head and (try to) wiggle it: if it moves at all, find out why.

This sort of failure can be coincidental with the upgrade, as machine problems can crop up at any time. Happened to me, might be happening to you.

Yes, Big CO2,
OMG!! Thank you!!! I have been pulling my hair out with this. And it was actually something very simple. Everything was completely tight. And I was little bit concerned. But then I remembered I just cleaned my lens so I thought I better just recheck it. And sure enough I did not have the lens holder tight against the lens. This is the first time this has happened to me in the 3 years I have had my machine. And it never occurred to me my lens being loose that it would cause something like this. Now I know.
Back to work!
Thanks again!

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Ah HA! Shifty lens is shifty!

With the lens fastened down, you should now verify any changes you made to the machine configuration remain correct.

If you changed the PWM Rising Edge Valid setting for the X axis, run the same tests that slanted before and see if they come out correctly. This change may have been due to the upgrade or it’s just one of those things that this pattern exposed while none of the previous ones ever did.

You should certainly recheck the Scanning Offset Adjustment to be sure the engraving endpoints come out nice and tidy.

Glad you’re running again!

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