Dime sized burns on mirrors inside resonator 1

[arktech]

Can anyone tell me why my mirrors inside the resonator develop dime sized burn spots and begin to deteriorate within three to four weeks after installation? My machine is a bystar with a 2800 watt resonator. Any help is appreciated.

 

[REVDRX]

I experienced a similar problem with A Fanuc AF4000E resonator in an Amada Pulsar 2415NT. About 3 months (2500 hours) after we got the machine all the fold mirrors in the resonator exhibited the same type of problem you are describing. The problem was caused by an improper laser gas mix due to a leak at the laser gas bottle regulator. The carbon dioxide, nitrogen and helium in the laser gas all leak at different rates resulting in improper laser gas ratios. The solution for us was to replace all the fold mirrors, laser gas regulator, hoses and fittings. Once everything was replaced we carefully checked for any laser gas leaks before running the machine. Since then the machine has not had any problems with the fold mirrors in 6+ months.

 

[arktech]

Only two of the mirrors in this resonator are exposed to the process gases, those two are fine. It's the three after the output window that are the problem.
Next week I'll post pics of the portion of the machine where the problem shows itself.
Thanks for your input.

 

[jetrep]

I would guess the mirrors aren't getting proper cooling or impurities are entering the beam path.

The path the laser takes from where it exits the resonator to where it reaches the focus lens has to be clean and free of impurities. The machine we have accomplishes this with encapsulating the entire beam path with flexible bellows. I believe there is always positive airflow through these bellows with cleaned/filtered air to keep debris from getting on the mirrors.

 

[Foostrap]

Make sure your bellows have no holes; usually the folding points of the bellows are the first to deteriorate.

 

[arktech]

Thanks for your help guys, I'll dig a little deeper tomorrow and try to figure out where the debris is entering the beam path. I'll respond again as soon as I have definite evidence.

 

[krugtech]

rebuild your shutter. the bushings are shot. the spots are bushing material. with the machine off take out the tube between the output window and shutter, stick your finger in the shutter cone and try to move the shutter, me bets it clunks w slop. jetrep and footstrap advice follow it too.

Chris Krug

http://krugtech.com/

Maximum Up-time, Minimum BS

 

[arktech]

Thank you Krugtech, you were correct, the bushings were shot. I cleaned and repaired and installed new mirrors. Now I'll follow up with an inspection in a week or so of the new mirrors. Thank you everyone.