Coating Solution contain Precipitates

[asanarina]

Hi! I'm currently give support to the coating department for their new 1.6 FSV lenses using the PPG 1.6 coating. We use SCL CD1000 machine.

Lately we found many rejects (we called "blob"). The whole lens is full of this blob and it seems to stick on the surface. I believe that it came from the coating solution because when I check the coating solution, there are lots of coating precipitate. However, we still unable to trace on where it came from.
During production, the first 4 hours it was ok. No rejects at all. But after that this reject appear suddenly. It cost 50% - 70% rejects per job sheet.

Do you guys have any ideas where does the coating precipitate came from? We already made sure that the lens are clean (checked right before dipping into coating tank) and the ovens are clean also. Where the precipitate came from is worrying. Because it disturb the long-running production.

Thanks

[Mauro.Airoldi]

I have a couple of CD1000 in my production department, if you put the enlarged photo of the defects, I can suggest its origin.
What degree of filtration do you use for the coating? (the suggested 1-5 microns)
the HC concentration (dry residue) is ok?
after the first tanks with basic washing, do you have a tank with an acid ban to correct the superficial pH? (if not, after about twenty lens baskets you will begin to modify the pH of tank HC)
I'm waiting for the photos to give you more suggestions.

[shubhendu]

Hii, @MAURO I have some query regarding the same machine & process,hope u help.
1.tank 1 & 2 with naoh+ water+ultrasonic is it only cleaning or some impact resistant property added to lens.?
2.tank 4 is it a buffer solution,acidic or basic?
3.in 6 & 7 how di- ionisation happen by the help of resin?
4.what is the type of this resin.

[Mauro.Airoldi]

1 these are only products that are used to clean the lenses, they have no effect on hardness, of course if you use lenses with a protective coating on cx, this will be affected and / or removed.
2 itself is a buffer and should be slightly acidic
3 deionized water is limescale-free water, limescale is removed from ion exchange resins
4 these resins are called ion exchange resins, they can stop positive, negative or both ions (we have to use those). The resins must be replaced when they are no longer performing (conductivity> 1 microsiemens). If you do not want to wear the resins too quickly, you have to feed them with water that has already been previously treated with a permeator.