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Thread: Hardcoating problem

  1. #1
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    Crier Hardcoating problem

    We are experiencing a 'line' during dip hardcoating which, at first sight, looks like a tooling scratch, but under the microscope is revealed to be a chain of very fine bubbles.

    We have the same lacquer type in another machine where there is no problem, and we had the same problem in the original machine when there was a different lacquer type installed. The problem is not seen till the lacquer dip stage, but changing the pump, and even installing the lacquer in another tank on the same machine, does not resolve the issue. We are confident that there are no air bubbles in the system.

    Has anyone ever seen anything like this before? Or has anyone any ideas what may be causing this?

    P.S. the marked lenses are extremely difficult to strip, if this helps.
    Last edited by Falstaff; 08-13-2009 at 03:44 AM. Reason: typos

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    Which kind of substrat material, have the lenses have an RLX Coating on the front curve?

    What kind of lacquer are you using?

    Are the problems only on plus or also minus lenses?

    Check clamping of the lenses, come the "scratches" stright from the point you are clamping, the problem may be also there.

    Lacquer tickness?

    Temperatures?

    Machine?

    Can you take picture with you microscope
    Last edited by Rafael; 08-13-2009 at 04:31 AM.

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    Difficult to do an analysis based on your information. Assuming it is really a fine line of bubbles and also concluding that it happens independent of lacquer batch or tank or pump it could be a decompression / degassing of the lacquer within the circulation/distribution system. So, even if you fill in the lacquer without bubbles, through venturi effects and decompression bubbles might show up at certain points. First I would check if your lacquer circuit is air-tight, i.e. not drawing air from outside, this would be only on the suction side piping of the pump. Secondly check the filter, bubbles could be created there when passing through the membrane (high delta pressure) if loaded heavily towards end of its useful cycle.
    Did you use the same circulation/piping system when you switched to the other tank trial in the same machine?

    The ....difficult to strip.... makes no sense if it is just genuine bubbles.

    What hardware and lacquer are you using, what did your machine/lacquer supplier say to all of this? We need more info to really help.....

    Georg Mayer

    Better Best then Biggest

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    More Info:

    Thank you for your replies. The effect, which I can only say LOOKS like fine bubbles, is on all lens types. It is, typically, away from the sides of the lenses, and so shows no influence from the grips holding them in place. At one stage we wondered about possible cavitation from the pump, but the pumps have been swapped with those on other tanks and machines, and we cannot see that this can be the cause now. The effect shows little similarity to that caused by the presence of normal air leaking into the system. Visually, there are no bubbles in the tank visible to the naked eye. The effect has survived the changing of lacquers and filters, so we are at a complete loss as the cause. We have yet to contact the suppliers of the hardcoating machine, who I can only say are a well known, multi national supplier of such equipment.

    There is nothing unusual, or out of spec, about the temperatures or lacquer thickness. Unfortunately, I am not at liberty to disclose either the lacquer, or the company which makes the coating machines. I can say that the on-line lens prep is through a highly alkaline bath with ultrasonic cleaning, followed by rinsing, a weakly acidic cleaning bath, and final D.I. water rinsing.

    Falstaff

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    Bubbles or line, why harder to strip ?

    I think we should follow the "....harder to strip...." more. Is there anything in the previous process of these affected lenses different or changed recently, say in surfacing or supplies which might still be on the surface of the lens ? BTW, are these bubble-lines on both sides or just on one side of the lens ? Are the lenses immersed hotter than usual from last drying to the lacquer tank ? Is a cool down step skipped (program error) before dipping, could this explain the better bonding to the surface (difficult to strip) and the creation of bubble lines?

    Have agood weekend

    Georg Mayer

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    Bubbles or line, why harder to strip ?

    think we should follow the "....harder to strip...." more. Is there anything in the previous process of these affected lenses different or changed recently, say in surfacing or supplies which might still be on the surface of the lens ? BTW, are these bubble-lines on both sides or just on one side of the lens ? Are the lenses immersed hotter than usual from last drying to the lacquer tank ? Is a cool down step skipped (or heater running hotter) before dipping, could this explain the better bonding to the surface (difficult to strip) and the creation of bubble lines?

    Have a good weekend

    Georg Mayer

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    So many optical types refer to hard coat as Lacquer that it leads me to wonder, is it truly just lacquer? The same or similar to that found in paint stores? Also leads me to wonder if polyurethane wouldn't be better. A further thought that since Trivex and Phoenix are polyurethane, do they need a hard coat at all?

    Chip

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    "Lacquer" is a generic term used to describe the hard coat liquids. The hard coat liquids are not, in fact, the same as lacquer you would buy at Home Depot.

    Trivex and Phoenix are NOT polyurethane. Based on the Bayer rating of naked Trivex (which is noticeably lower than uncoated CR39), all Trivex manufacturers recommend a hard coat.
    RT

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