Lines down the cutting edge of acrylic

Hi Guys,

I have just bought a second hand rdl4040 50w CO2 laser engraver with little use on it, and I’m having problems with the cutting edge having lines every 5mm. I read the post below, but im not sure which wheel to adjust/reinstall.

Having just realigned and cleaned the mirrors and got the machine to start cutting

, this is really disappointing to me.

I would appreciate any help on getting this fixed.


Hi Andrew,
Is that the bottom side of the cut? Can you take a photo of your cutting bed?

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With two axes, the first step is to determine if one or both axes are affected. Most likely it’s one of the pair, assuming it was working previously.

I’m sorry, but I can’t figure out what I’m looking at in the photo… :face_with_spiral_eyes:

If you use a honeycomb bed, that can cause these types of marks. Although they seem pretty large for this. I think that’s what @Rob_H was driving at.

As far as alignment goes…

  1. properly working tube
  2. clean and aligned optics
  3. proper focus

If you have these three, they work …


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If you raise your work off the bed that goes away.
Go to Youtube and search Honeycomb bed standoffs & you will find a plethora of usefull information!


Here are the pins I use, you would have to change the size to fit your bed.
They are good because you make them out of your scrap material!
4mm bedpins.lbrn2 (42.3 KB)

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My honeycomb only lasted a day or two before I swapped it out for a sheet of rolled steel. The honeycomb totally ruined the air flow through the machine.

I’ve never seen a reflection that far across the material? Where do you focus and what lens do you have.

These anomalies start large and grow smaller… The beam is growing once it passes it’s focal length and a reflection adds to distance. If it’s 3mm, then it’s 6mm back to the top of the material, best case…

It looks like a mechanical issue. What axes is this, does it occur on both axes?


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Hey Rob, had a bad week this week and totally forgot to do this in testing the machine (even though I do know to raise and put a bit of wet kitchen towel underneath as per a trotec video I watched). Proper cheered me up mate seeing the nice clean edge. thank you. was not a lightburn/machine problem, was a me problem! :sweat_smile:

smooth as a baby’s bottom :+1:


Looks nice, I find it hard to believe you were getting such a powerful reflection…

When you cut something. you want to use a vast majority of the power up by the time the beam exits the bottom of the material.

If there is enough energy to reflect back up, out of focus and do damage all the way to the materials top, I think you have too much power applied initially.

Just MHO… :crazy_face:

Glad you resolved the issue …



I keep mine because I have a 2Hp blower on the exahust and it has enough power to turn the bed into a vaccum table. I cut a lot of paper templates so I built a jig to hold the paper and when I block off the rest of the bed it supplies enough vaccum to hold the paper in place and I can still use air assist for the cut.

Andrew, good luck with the new machine.

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