laser engraving problem

[anaelfphone]

Hello!
I work with lasercut 5.3 and on machine JQ 9060 and it worked very well for 1,5 year.
But in last 10 days I have problem with engraving. While engraving there is "shadow". It looks like it doesn't start engraving with full power. You can see best what is going on on this image.

aaaa.jpg (13.83 KiB) Viewed 5568 times

Like it starts with low power and after some time it gets full power.
So this is result of engraving

aaaa.jpg (13.83 KiB) Viewed 5568 times

Notice the shadow on letters and not equal engraving...
Lenses and mirrors are ok, and i have no problem with cutting, onla engraving. What it could be?
Thank you for your answer!

[anaelfphone]

I'd double check mirror alignment and make sure they're clean. Also have a check of your focal lens make sure if is not cracked and it's clean.

[Geraldol]

I think there are two problems. First make sure that laser beam Comes out of the nozzle centered. If not it could cause shadows. Second ist laser power when starting engraving. This could be caused by a laser tube which loses power.
It's quit normal that a laser tube loses power after some time and I also had that Problem. After putting in a new tube the problem was gone.

[Wayne Rees]

Do a spot test with a piece of wood in front of one of the mirrors, if you have a nice round dark dot the beam is OK, but if you have a ring or doghnut shape this will give the results you mentioned, what is the step gap you are using on your settings