Aligning mirrors, laser burn mark is ring shaped

[enricosanchez]

Hi Cnczone, I'm attempting to diagnose a drop in power on my 100W Thunder Laser Mars. The machine is around 1.5 years old.

Cleaned mirrors & lens, aligned mirrors, but still low power.

I noticed the burn mark when aligning the mirrors is creating a ring shape, which as far as I can recall, it wasn't doing before. Does this mean anything to anyone, I can't find any references to this issue in the forums.

Here's a photo



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[cinematic2]

Is this the same before first mirror? If so just the time to buy new laser.

[OldEngraver]

Best you contact Nolan at Thunder Laser I'd say. Always appears quite willing to help.

[enricosanchez]

Thanks for the feedback. I've contacted Ben at Thunder laser in addition to posting here. Ben has so far suggested turning the laser power up above 30%, which instantly ignites whatever object is unfortunate enough to get in the beam path I'll post back any more feedback I receive from their end.

Is this the same before first mirror? If so just the time to buy new laser.

This sticker is sitting just before the last mirror.

[MConner]

Dang, that is a solid fault symptom. I like cinematic's idea, do you see it before the first mirror? This may sound condescending, but have you cleaned the laser output lens?

[enricosanchez]

Dang, that is a solid fault symptom. I like cinematic's idea, do you see it before the first mirror?

Ben from Thunder Laser recommended the same as you guys, the image below is a piece of cardboard which ships with the machine with three marks burnt at the tube output (before the combiner). The new marks are measured at 30% (recommended by Ben) and 15% you can see the ring pattern.

EDIT: Ben replied to say that the laser tube is unstable below 30% power. The best performance is between 30-70%. He suggested I clean my mirrors :-( I'll try buying some new mirrors and re-align the whole thing again.

but have you cleaned the laser output lens?

Do you mean the beam combiner?

[MConner]

Interesting to learn about the low power stability issue, that is a good thing to know. By output lens, I meant the actual output end of your laser tube itself, inside the gold metal ring in your picture. I have seen residue build up on mine occasionally, most likely from doing test shots with the exhaust off, or collection dust. Good luck.

[enricosanchez]

Thanks for your replies, I'm going to go with "dirty mirrors" and replace them. Ring is normal below 30% power. Machine is great by the way, buy Thunder Laser!!

"dirty mirrors" and replace them.

I should specify, I have cleaned them already but can't get them super clean.

[speedy_j]

Hey, did you solve this ring shaped mark problem? Was it the tube?
We have the same problem, but our tube is at 650 hours and it's too soon for its end.
We have moved to a new location and turned the machine on one side in order to make it through the door (the machine is huge). Maybe this is when something happened?
The following two weeks we cut a lot of acrylic (successfully).
Now the machine still cuts ok (with slightly lower intensity), but the engraving is messed up completely.