OMTech laser is great – but it leaves strange marks on the edges -> photo inside

I have bought and set up the 60 watt OMTech 40x60 laser… Everything went smooth (also thanks to help from forum members), the machine works great with Lightburn (via iMac and MacBookPro).

The cuts are beautiful, but there is a mysterious phenomenon happening on the edges of my cuts (see attached pictures. These very slight indentations appear about every 10 mm.
They are on ALL cuts, this has nothing to do with the file…
Does anyone of you have an idea what this might be?

Thanks, Mirjam

Do you know if these happened on the X or Y axis or both?

Do they happen in one direction or both directions?

There might be something caught in the drive gear or the belt is getting hung up on the drive gear.

Hi, thank you!

It happens on both axis…

Drive gear… ok, have to figure out what to look for!

What speed are you using for your cut?

Two other members are seeing a low speed artifact in some projects that appears to be caused by the motion planner in the GRBL controller software.

Thank you!

It’s not GRBL, it’s a 60W CO2 laser, controller is KT332N.
Speed is 25 mms, power 35 % - the material is 1,5 mm matboard.

Sorry about that, I clicked on your profile and saw the 3018 and overlooked the OMTech info everywhere else.

Is the belt tooth pitch inside your machine 10mm? an incorrectly tensioned belt can hang up as the sprocket rolls on it.

Do you mean this?

Wouldn’t an incorrectly tensioned belt also cause inaccuracies in the cuts?
Sorry, I’m just guessing! :sweat_smile:
I’m not having other “problems” (so far).
The indentations are very slight, barely visible on the front side, but there are tiny leaks on the backside. I’ll post a pic of that.
I just wanted to make sure it’s not an early sign of bigger problems to come.

→ Have to update my profile too! Thank you…

Can you see those tiny specks along the edges?

I sure can. Do they by chance line up with the honeycomb on the bed of the engraver?

Oooooh! Yes that might be it!
But why…?

Probably because the heat on the honeycomb reflects back and burns the mat board a bit?

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There are several opinions as to why this happens. My belief is that the honeycomb can throw reflections, disrupt air-flow, quench or heat-sink ablating material.

Several folks here are making jigsaw puzzles and have switched to other bed materials or installed ‘punk spikes’ or used golf shoe cleats to space the work up off the honeycomb.

Oh, I see - that makes sense… Thank you very much!
Have a great day, Mirjam

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