Divergent laser beam and imperfect cuts

We have a Chinese laser that came with a 150 to 180 Watts Reci tube which broke last week after 5 years. It looks like there was a short circuit because the high voltage connector was burnt, so we replaced the high voltage connector.

We had to buy a new tube. We went for a Yongli tube, 130-150w.
The issue now is that the laser beam seems to be divergent, when we shoot at the first mirror we get relatively small dot. I have attached an image with different power intensities shot straight from the larr end below.
At the second mirror it grows bigger and at the third one it is already very big. The washers inside the laser head were burned because of the big diameter of the laser beam.

Additionally if the the laser beam is powered on a low power such as 13% it leaves a dot like a circle like a ring instead of a full circle. I attached an image.

Regarding amps I know we are supposed to work around 24 amps and the maximum powers should be 80%, however the issue is that at 80% we have around 36 amps instead of 24.
The tube is from 2021 production year .
The cut is almost all right.Apart from the fact that we can observe melting/ some bubbles on the top of the material.
The laser mirrors have just been calibrated and aligned.
I am interested in finding out if the divergence is a sign of a defective tube and what could be the cause for the bad cut and how to solve it.
Thanks :slight_smile:

Yep, looks like you have a bad tube. You should make a similar density mark before m1 (mirror 1) to ensure the tube is resonating or in TEM00 mode.

That looks like your issue from the first photo… that is more like TEM01, which will never work correctly… has to be TEM00 mode…

See if this thread helps…


Ok, thanks for replying.