Surface of SI mirror just crumbled off.....

thejuggernaut
Posts: 89
Joined: Fri Sep 27, 2013 11:08 pm

Surface of SI mirror just crumbled off.....

Postby thejuggernaut » Tue Jul 25, 2017 6:25 pm

I bought new optics about 4 months ago after my old ones were starting to get a little worn after several years. I have used them for 10-12 hours, and they have been sitting, covered to keep dust off them, for about 3 months. Tried to use the machine today, but wasn't getting clean cuts. I started to do an alignment, and noticed a bunch of little bubbles all over the entire mirror that looked like water droplets. I got a clean glass cloth and the second it touched the lens, the entire coating on the lens crumbled off. The lens is now completely silver instead of the yellow color it was before. All of the other mirrors and lens look pristine and brand new. Is this a common issue with lenses? Just trying to figure out what could have caused this, or if it was a coating defect. I have never used any cleaners on it, and have never even had to clean them because they have been covered when not in use and remained clean.

bluecuriosity
Posts: 9
Joined: Wed Sep 30, 2015 11:19 pm

Re: Surface of SI mirror just crumbled off.....

Postby bluecuriosity » Tue Aug 08, 2017 1:11 am

Those coatings do not have great adhesion to glass. The surface will develop micro stress cracks over time primarily due to the difference in thermal expansion between the plating and substrate. If you notice any wierdness in the beam profile after it has passed through the circut of (clean) optics then it is time to replace.

The degredation is faster vs higher wattage beam. Also faster on dirty mirror.

Solid mirrors will last longer than gold plated and are generally preferable due to above.


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