Etching paint off of aluminum, beam reflecting back through beam path

Hi All,

We’ve been shooting paint off of aluminum plates and the beam is reflecting up the beam path. We noticed it when the aiming laser cut out - investigating revealed that the aiming laser’s lens was melted. Which begs the question how much damage does this do to the laser tube itself?



Probably not much as there is no real power in the beam when it goes backwards… especially through the lens good or bad.

Aluminum reflects some 99.6% of the light because of the molecular shape. I’ve fried a lens with a stainless ‘engraving’.

I use LBT 100

on this stainless mug…

Good luck…


I’m running a 130W laser and it’s bouncing back enough energy that is melted the lens of the aiming laser and can burn a hole through a piece of paper that I set in place of the aiming laser.

I love the LBT-100 as well. Problem with this process is that we’re doing an inversion - applying a coating, then blasting out shapes. With LBT-100 you’ve always got the ceramic particulate between the beam and the metal, so I’ve never really worried about it. Now I’m afraid that if it can damage the aiming laser’s plastic lens, can it damage anything else along the beam path? The tube itself?

Also your LBT-100 results look great!!

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Do you have your power turned down to minimum?

What is the lowest percentage will it lase?

Is that where you are at now?

I was suspicious about it being rather a powerful machine.


Yeah, we assumed some power setting based on previous jobs, but I’ve got a power setting bracket test prepped. I’ll report back with results.

I would imagine that since the laser tube and mirrors can handle the power the tube puts out, it stands to reason that after reflecting off the work surface, there is some considerable power loss and not likely to damage the mirrors or tube. The aiming laser lens being plastic is opaque to the CO2 laser and would soak up all the infrared power that hits it.

Thanks Fred! That’s the bit of logic that my fear keeps trying to undermine. Now I just need to figure out how to keep the bounce back from damaging anything that was behind the aiming laser for the remainder of this job.


Do remember that the laser beam (once it goes thru the lens) is a converging beam of light. Once it passes it’s focal length, it diverges and expands at the same rate that it converges. As Russ points out, due to the nature of the laser beam, the central portion is still pretty powerful but not at the level of a focussed laser. How it reacts as it goes back thru the lens is another story, but less likely to result in a proper straight laser beam.

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