Mirrors/lens shot?

Hello again everyone!

Long story short(ish): when we first got the laser, we didn’t realize the air pump was barely working; there was a TON of smoke and a LOT of flair ups. I was having a really hard time cutting through 1/8 ply in one pass at 75% (“60” watt laser).

Fast forward to today: new air assist, re-aligned and focused (ramp test). I can get through 1/8" ply in one pass, at the top of the machine only. I’ve double and triple checked the alignment and if it’s not perfect, it’s close enough that I can’t tell if it’s off. Same problem.

On the last alignment check, I noticed that when I hit the pulse button, the tape is clearly burned through when the head is at the top of the machine, but when it’s at the bottom I have to hold pulse longer, or double-tap it to get the same marks.

I cleaned the mirrors and lens (so dirty from the early problems) but I still see marks on mirror 2. I’m assuming that my mirrors are shot and this is the cause of my current problem. So before I order new mirrors and a new lens, is there anything else I need to check? I already have a 6" inline fan on order to boost the exhaust (it’s a 20’ run of ducting to the ceiling vent)

Thank you all again for the support!

Even if you have adjusted your laser beam I would highly recommend checking it again. The mirrors should show the same result in all 4 corners of your machine bed. And it has to be right.
In addition to the “simple” mirror path adjustment up to the nozzle, adjusting the nozzle vertical setting in x and Y direction is reasonably important.
Another source of error could also be the difference in bed height, but it is easy and quick to check.
With my brand new 60 Watt machine, after setting the horizontal and vertical direction of the laser beam and some material tests, the lens in the nozzle was already very dirty. This is probably due to the small air flow from the built-in compressor, the compressor location (thanks to LaserWillie "for making me aware of this) and the performed nozzle centering test, with tape on the hole.
Try again, it should probably work for you too. :+1:

I use mine, during alignment, at very low power. It’s a China Blue 50 watt. At the back/left, I can make a nice spot. Moving to the front/right, I have to hit it multiple times just to see it.

Short distance to long distance. The beam widens as it travels and as a result the average power density of the beam is lower.

You can put a piece of tape on it and hold it on the nozzle.

Beam Checker 2.lbrn2 (12.2 KB)


Such an incredibly frustrating experience!!!

Mirror 1 to 2 is dialed in. If I use the same piece of tape, there’s no additional marks from front to back; it nails the same hole, same size. I’m taking that as I know how to align the mirrors. I cannot get the same level of accuracy from mirror 2 to 3. Even when I hit the same spot, the hole enlarges. (yes, I normally use 2 pieces, overlaid, to make sure the two spots line up)

Mirror 2 looks like it has a small smudge on it, but it’s not a smudge since it shows up again after cleaning it. My little brain keeps telling me this is the issue, but then there would be a problem cutting in the upper right corner, not just the lower right, and there isn’t.

Anyone in the SF Bay area want to make some extra cash before the holidays? lol ARGH!

@ jkwilborn - How exactly do I use that? I’m clearly missing something here. :slight_smile:

Put a piece of tape over the end, place it over the nozzle and fire your machine. You can see if it’s centered or not.

You advise that the beam hits m2 in the center properly at any point. That would seem to indicate that it was an issue with the head alignment.

Might be helpful to post pictures of the ‘beam’ marks for others to examine. Maybe someone will see something you didn’t…

If the ‘smudge’ is within the beam, that’s problem.


Out of desperation, I rotated mirror 2 180* (the smudge was a little off center) and re-aligned. Much better. I’ll probably get a new mirror set next month, maybe a new lens too.

Thanks again!

Maybe a good idea…

What is there to re-align? Simple mirror change.


I managed to lose the mirror removal tool and the housing for the mirror is just mounted on thin bent sheetmetal; it flexed a bit when I used c clip pliers to unscrew it, (the “screw” was really tight) and the beam was off-center quite a bit after that.

When I order new mirrors, I’ll get another tool. Hopefully that, and a slightly looser screw, will keep it from flexing again when I change the mirror(s)

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