Shattered Lens

Discussions on optics for laser cutter/engravers

Shattered Lens

Postby twehr » Mon May 16, 2011 1:48 am

In my test and review of the rotational adapter, I mentioned my Emergency Deadline Detector. Everybody has one of those. It is usually in the form of system failure or mechanical breakdowns just as you are approaching a deadline. In my case, it was a double deadline - finishing the adapter test and writeup and craft show I have to do on Thursday - need to finish a lot of product before the.

It started with the office this past week - everything that could go wrong did. And since I am on call 24/7 (even when on vacation), it meant about 70 hours of work instead of the usual 55 or so.

Today, I was working on product for the craft show. Everything was going really well. Then, all of a sudden, I was getting a very weak beam at the workpiece, and I noticed it was actually a double beam. My first thought was dirty optics, so I clean the mirrors, which needed it, but did not fix the issue. So - remove the air assist and remove the lens to clean it. To my surprise, the lens was in pieces.

[Photo - shattered lens]
Broken Lens 1.png


Don't know what caused it, but there it was.

When I built the new laser, I stared out with the old optics to ensure I did not screw up new mirrors and lens during the build and initial alignment process. I've been meaning to swap them out for the new ones I had waiting, but had not gotten to it yet. SO, I happen to have a brand new lens just waiting for me. I put it in and everything is great.

I also noticed that the locking nuts on the mirror #2 adjustment screws were loose and vibrating. (Everybody go check yours now.) I did not swap out the mirrors yet - everything is working well and I don't want to take time to go through re-alignment if it moves while installing the new mirrors. When I do, I will re-align and then make sure the nuts are all tight.

Lesson? Keep extra optics around just in case.
tim
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Re: Shattered Lens

Postby bdring » Mon May 16, 2011 2:01 am

I was thinking the other day about the issue of the lens being too small for the holder and I though if you cut a ring out of acrylic with a slit through one side and the ID were just a bit smaller than the diameter of the lens, it would sort spring fit on the lens and might center it. The OD would be cut just right to fit the lens holder.

If the acrylic were the right thickness it might take the clamping pressure instead of the lens when tightening too.
Bart
"If you didn't build it, you will never own it."
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Re: Shattered Lens

Postby dirktheeng » Mon May 16, 2011 2:07 am

It is possible to shatter a lense on a high power laser if it gets dirty. The dirt/oil will cause heat absorptioin and heat stressing in the lense. We frequently have that problem with our high powered lasers in the lab (but they are 100+ Watt lasers). Just a thought.
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Re: Shattered Lens

Postby LeonS » Mon May 16, 2011 12:08 pm

On my older laser, I cut out an adapter just as Bart suggests. It works great. It centers the 18mm lens in the 20mm holder perfectly. It would have been difficult to fabricate the spacer without a laser cutter.
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Re: Shattered Lens

Postby trwalters001 » Mon May 16, 2011 12:57 pm

I made mine out of Delrin on a lathe. :shock:

I would definitely do it with the laser next time.
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