Overscan issue?

Laser: Atom stack A5 M40 40w(5w optical).
Modified x-gantry 2040 extrusion + 3mm steel mount. Modified y-gantry synchro rod delete added dual stepper motors.

Settings: 1000mm/min, 50% power, .15mm line width, varying overscan amount set.

I’m relatively new lasers so please forgive me if I’m overlooking something dumb. I’m not new to this style of machine though (5-3d printers and mpcnc). I’ve gone over the machine it’s self to rule out any hardware issues.

After much googling and testing it really seems like an overscan issue or possibly backlash on direction change.
The numbers correspond to percentage of overscan set in lightburn. Though it doesn’t seem to change anything. Don’t mind then ugly numbers in accidentally left that layer set to 10k mm/min.
Sorry for the formatting I’m on mobile.

Try turning off ‘Bi-directional scanning’ on the fill layers.

If that makes it pretty, you likely have a loose X-axis belt or pinion somewhere, causing the reverse pass to be offset from the first one.

Okay so I found out how to adjust for back lash. It cut down on the issue a lot but still a little offset on the text. Turning off bidirectional scanning did fix the text it came out crystal clear. Tore apart the machine again and couldn’t find anything wrong. Tried a box with bidirectional scanning turned on and it came out with clean edges. I stopped the box engrave early. Text still has issues in bidirectional scanning.

Edit. Ran another full card. It appears my text on both edges is clean and it’s no over run. But everything in between where the laser turns on and off is the issue. As shown in the last picture.

That looks to me like your belts (Stepper motors) are out of sync. Try manually and slowly moving your laser to the top right corner. Then back it off a few inches and slowly run it into the corner again. Then home it and set the origin and try again. I’ve fixed this a few times on hobby diode lasers at my friend’s local maker’s den.

It sounds like you know what you’re doing, but sometimes the simplest things confound the smartest people…

Thanks for the advice unfortunately it did not seem to help.

How much dpi do you use? Try 254 dpi.

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