Laser burning text twice off by about 2mm even though it only does a single pass

I’m trying to engrave text and I’ve found a few times that the laser appears to engrave text 2-times about 2mm apart, even though it only passes once. I’ve adjusted the laser to a point, so I believe it’s focused correctly.

What are ways to fix? I’d tried adjusting from fill to line. I’ve tried masking tape to reduce burn. I’ve adjusted the power. It’s still appears to be off. Any help is appreciated.

Laserpath aligned?

How do I test that? Ive squared the laser on my work area and made sure it was lines up. But I’m new so I’m open to new tips.

@OrturTech any suggestions? This is for my new Ortur Laser Master 2 20W (2021).

Thanks for the help.

Engraving on leather with text typed directly in to lightburn. Using recommended power/speed.

For clarification
Is this same job 2 passes?
Or you running the same job twice

If the first i would think X is moving too fast and might need tightening on the belt as it looks like its losing steps

It’s one pass and a single job. Which is the weird part. First attempt I did have 2 passes (carryover from previous job). But I changed that and am still getting this result.

Speeds? I assume being leather its quite fast
Try this on scrap cardboard
Run job as is once (even with 2 passes)
then cut speed and power in half
Run again

If the 2nd job ran perfectly it means the X belt needs tightening and at high speeds its losing steps

Ran the test with speed / power percentage written next to each one. Still seems off.

Height of each line is 8.5mm. not sure if that helps.

Definitly something off on your X belt
I would review all but if you can, run that test again (even at 1% power) at 3000mm/min and record on video upclose the belts. as they move i can see if they are loose or not. both X Y left and Y right
If they are flapping about inside the rail they need tightening

Can upload to (refer in comments the link to this post please)

Thank you. Just uploaded the video (about 3 minutes long) and tried different angles of the belts. Let me know if you need a different one. The safety goggles made it hard to make sure I was capturing the best angles :grinning:

That’s not burning two passes, it’s the ‘return pass’ being misaligned with the outgoing pass because the belt is either loose (most likely) or too tight (less likely, but can also cause this).

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I tend to be an over-tightener whenever I build things.

How can I make sure the belts are correct. Do I let them be naturally tight enough (no pulling it taut or feeding it back in to loosen it)?

Finger-tight only. No ‘boing’.

Loosen off, pull the pinion to take up the slack, only, nip up and tighten

Nothing should deflect in the pinion and stepper mounts if you pinch the belt together

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Thank you, everyone! The x was too loose. I didn’t get it to 100% perfect, but I was able to get about 99%. I appreciate everyone’s willingness to weigh in.

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From the video you sent all belts need tighetning
Specialy X + Y right side (cant see well the belt on left side)

In this case the problem gets more notorious on the X because the lateral left/side motion
As the laser head reaches the end of the line -> slows down _> stops > reverses
The steppers pull to start moving the other direction but as the belt is loose those 0.5mm of initial motion simply are used to apply tension to the belt, THEN the motion starts. So you get 0.5mm each side of “slack”

You need to tighten them all nicely
Now Tight is a very subjective term but when you look at the belt on rest (no motion) in the vslot they should be in tension and not drooping into the slot
Made this very crude referece just so you can see how tight they should be. Again very hard to put in words even on video but if you press them near the sprockets they should not move more than a few mms

Thank you! This is very helpful.

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