I upgraded my 60w CO2 laser to 90w about a year and a half ago. In conjunction, I “upgraded” the OEM (Monport) mirrors to coated silicon mirrors from a respected American-based vendor that I’ll decline to name.
I noticed about a year ago that the coating on the mirrors was failing - tiny golden flakes on the Q-tip when cleaning with IPA. I contacted the vendor and they sent replacement mirrors.
I recently had issues with the laser cutting 3mm Baltic birch and was getting a double line out of the nozzle. I went through the mirror alignment process using the traditional “burn masking tape” method. Once complete, I went to clean the mirrors using a Q-tip and IPA (as recommended by the vendor - who is also the manufacturer) and was disappointed to once again see gold flakes on the Q-tip.
I removed the mirrors and put the OEM mirrors back in and tweaked the alignment (surprised me a bit that I needed to re-tweak, but maybe there’s a slight difference in thickness - it was only a slight adjustment) and completed the project I was working on without further issue.
I contacted the vendor and they are again graciously sending replacement mirrors. On the first replacements, they told me that they had bad batch of coatings. No explanation was given for the second failure.
The laser is in my central Florida garage and subject to the typical Florida heat and humidity. The mirrors are only cleaned using a Q-tip and IPA, as per the vendor instructions.
Questions: 1) anyone else experience failure issues with coated silicon mirrors, regardless of vendor/manufacturer? 2) Anyone have thoughts on why the failures are happening? Is the environment the issue?
I have never seen mirrors with such a ruined surface. I cannot/will not comment on what is causing this, but it fits nicely into the discussion we just had regarding the quality difference between cheap and more expensive lenses/mirrors. The price and country of origin do not always reflect the quality, unfortunately.
I have revised my opinion…
There are a few possibilities that cause coatings on optical elements to not adhere properly.
Wrong chemical mixture of coating, wrong temperature during evaporation, pollution, wrong tempering after coating.
Yeah, this company supposedly makes world-class optics. I have a set of their lenses and they’re great. Disappointed with the mirrors, but I’ll give them one more whirl. At least the replacements aren’t costing me anything other than some frustration.
I really think these mirrors are also from the “bad batch” that the first ones were from.
Yeah, I stick the tape to the mirror frame/cage, not the mirror itself. They get cleaned with IPA after alignment. Some residue certainly gets on the mirrors.
I’ll have to play around with some alternative targets. Thanks for the suggestion.
Yeah, I think the original mirrors were moly. They are at least uncoated and while not pristine, they aren’t wrecked either. If the replacement coated mirrors fail, I may go back to moly.
Rather than struggle with coated mirrors, why not switch to Molybdenum mirrors. They are solid metal, durable enough to withstand regular “scrubbing” with cotton swabs, IPA, acetone or other solvents and maintain their reflectivity. The 1 or 2 % reduction compared to new gold coated mirrors is trivial compared to long term use.
