Strange text effect

Hi all,

I’d like to start by saying this is my very first ever attempt at laser cutting/etching. I put the machine together last night (Atomstack A20 Pro) and followed the Lightburn tutorial to make a QR code wifi login tag.

Everything went shockingly well for my very first cut. It seems I got most of my settings right for the type of wood I was using and it was all generally very clear.

The weird problem though is the text at the bottom:

As you can see, it’s kind of squashed and slightly cut off.
If I put the text at the top it doesn’t happen

I felt my belts and/or rollers might have been a bit too tight, but loosening these up has made no difference, and when I move the laser manually, I don’t feel any resistance or “bumps”, so that left me thinking that maybe I did something wrong with the software.

Is there something that could cause this in software, or can this only be a hardware issue?

If you have AIR ASSIST turned on, and your small work piece is not secured to the work area, the air can blow the part out of alignment. Double sided tape works great for small parts.

This is going to be mechanical on the Y axis (up/down). Normally when LightBurn runs an engraving, it moves to the bottom, reverses, and engraves bottom up. When it reverses, if there is slack in the belts, it’ll take a while for that slack to be taken up, and the laser won’t actually start moving the other way until that belt slack is gone.

It could also be a loose coupling or a set screw that’s loose on one of the Y-axis motor pulleys, but look through those parts - it’ll definitely be something in there.

Thanks for the reply,

That was also my thinking, but when I start the etching on a completely different part of the work area, I get the exact same issue in the exact same part of the wood. I’d have thought if it were hardware, I would see the issue in a different place if I moved my work area.

Where did each of your engraves start? On each one you have a problem. Did the laser start on lettering on the first one and WiFi logo on the second one?

Which is because the mechanical problem is triggered by the relative motion, not the absolute position. No matter where you put the wood, the laser head will move in about the same way to get to the starting point, which is enough to trigger the backlash.

For example, if the laser head is at the far end of the Y axis, it must move to the bottom of the text before reversing direction when starting the engraving. The first movement sets the loose pulley at the wrong place, then the motor must turn enough to take up the backlash before the pulley starts moving again.

Nobody wants to believe that’s the way it works, but … that’s the way it works.

I agree mechanical seems most likely. Do t forget to check the wiring, air tubing, cable guides/ties, etc. You may be pushing up against something somewhat hidden or pulling something tight. It doesn’t always take much to make a difference.

Thank you all for your replies and suggestions.
I checked again, and one belt felt slightly looser than the other on that axis. So I tightened it up very slightly, ran the job again and it came out perfectly :slight_smile:
Thanks again,

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Bonus: You’re developing a feel for how backlash works.

Given the construction of diode lasers, you should expect something else to work loose, but now you’re ready. :grin:

You can also help yourself diagnose such problems by changing the engraving angle and observing the results.


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