Laser focus lense damage

[bill liscombe]

HI all,
This is my first post here and its a query about what has damaged the 2" focusing lense on my works trotec speed 300 80W laser engrave.

there is a "star" shape crack in the lense, which i suspect could be from someone not setting the focus depth correctly
below is a photo any ideas?[IMG]file:///C:/DOCUME~1/b2431/LOCALS~1/Temp/msohtmlclip1/01/clip_image001.jpg[/IMG]

[Rodne Gold]

No pic in the post , but damaged lenses are normally due to a build up of dirt/moisture/oil which either mess the coating or burn/overheat the lens.
If you have air assist which blows thru or includes the lens box, your compressor can be the problem , re moisture or oil.
It could also be mechanical damage , like the lens dropped etc.
Wrong focus depth would be unlikely to cause the damage unless the head containing the lens hit something?

[Art Anderson]

I cracked my first lens from dirt buildup on the bottom of the lens, caused by having the air assist running too strong and creating a venturi effect. The dust and fumes were actually pulled up onto the lens. Trotec recommends adjusting the compressor by loosening the locking nut and turning the adjustment valve stem clockwise (closing) until you feel resistance. This should be the closed position without forcing the valve seat. Mark the adjusting knob on the top. Re-open the valve counter clockwise three turns. Reset the locking nut. Done. While this is only a starting position, I found it to be a good setting. Often, I'll have to increase volume depending on the material flare-up, but I've learned to check the lens often.

Hope this helps,
Art
Trotec Speedy 300, 45 w.

[Mike Null]

Art offered the exact comment I was going to make. (my lens is now 6 1/2 years old and I use the machine every day.)

Check your lens every day--if it shows any sign of dirt clean it.

Being out of focus did not cause your problem.

Trotec tech support will send you the memo though Art has it right.

PS Welcome to SMC. Please reduce the type size to make reading easier.

[bill liscombe]

Thank you for the replys, ill look at the air assit the next time I am at work.
The problem is more than one person is authorised to use it and they don`t always clean it.
Sorry about no picture,when i posted the message the icon didnt appear so ive attached it to this reply
P1260004.JPG

[Art Anderson]

Yup.... I know that look....sadly said the credit card....

[bill liscombe]

Luckly it the company I work fors engraver, but its going to take two weeks for the replacement to come from Austria.