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Thread: Poly Cracking

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    OptiBoard Professional Mike Fretto's Avatar
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    Poly Cracking

    I know Ive seen threads along this line before but Im curious to know if this is an internal problem here or is it more widespread. We occasionally get poly lenses back from our outlying offices with cracks in them. Ive suspected in the past it was on lenses only and the lenses may have been slightly big due to poor calibration of the tracers in these outlying offices. Today I have a request for new lenses on a grooved rimless because the lenses have cracked. Im left wondering if theres something were doing wrong in the manufacturing process or is this a material defect. I'd read somewhere that poly has changed due to the release of blue-ray disks. Also where beginning to see LifeRx lenses coming back delaminating just as the original product had done. Am I the only one seeing this or are there others out there who would agree.
    Mike

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    One of the worst people here
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    Are the edges polished?

    Are the grooves finished up with a wet groove (you groove them dry, but then do a wet cycle at the end)?

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    There was recent talk on the Delamination thread (see below somewhere) that talked about LifeRx polarized lenses...

    Typically speaking, ANY polarized lens SHOULD NOT have the groove cut on or within at least 0.50 mm of the lamination line. This will take hands-on detail-oriented work by whoever is doing your grooving. Don't give it to an apprentice or someone who you just hired from McDonalds.

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    Rochester Optical WFruit's Avatar
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    MikeA, LifeRx aren't polarized, they are photochromic (I think you need to pull your head out of the glass and smell the plastic occasionally :p)........

    Mike F, Poly usually cracks when the lens is too big and too much stress is placed on the edges of the lenses. In the case of grooved poly, it can be (though usually isn't) from the grooving wheel hitting the lens. It's also possible to "flake" the poly in groove if the groove is too narrow for the liner/nylon cord. Also, make sure EVERYONE knows not to get acetone near poly. If anyone needs a visual reminder, just put some on a CD and show them what happens.

    As for LifeRx delaminating, as I said in the other threads, we've never had one come back for that issue. But I know a lot of other have. Vision-Ease improved and "fixed" the original issue, but they've since discovered that it's an on-going "improvement" process. Currently they said that it's now under .5% of their LifeRx coming back. And there are rumors of a CR-39 version on it's way to compete with Transitions.....

    :idea:USE TRIVEX INSTEAD:idea:
    There are rules. Knowing those are easy. There are exceptions to the rules. Knowing those are easy. Knowing when to use them is slightly less easy. There are exceptions to the exceptions. Knowing those is a little more tricky, and know when to use those is even more so. Our industry is FULL of all of the above.

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    OptiBoard Professional Mike Fretto's Avatar
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    We polish the edges on all our rimless jobs weve felt it just looks nicer. We understand the problems this can cause with reflections. Weve never tried grooving wet on poly that may help clean it up a bit. Any input on the possibility that all poly has changed with the release of Blue-Ray disks. How often have we seen a change to address one issue that creates other issues?
    Mike

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    Edge cracking on poly can be from a couple issues. The first has already been mentioned; lens size. The other can be due to too much heat build up during edging. ie. dull edging wheel. Make sure your rough, fining, and polish wheels are kepted up by using the truing stone every so often. Rough wheel can't be "stoned", it may need to be replaced if it's worn. We replaced our rough wheel after 4 or 5 years of use.

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    Quote Originally Posted by Mike Fretto View Post
    We polish the edges on all our rimless jobs weve felt it just looks nicer. We understand the problems this can cause with reflections. Weve never tried grooving wet on poly that may help clean it up a bit. Any input on the possibility that all poly has changed with the release of Blue-Ray disks. How often have we seen a change to address one issue that creates other issues?

    The polishing is done, because without it, there are cracks that can expand. With the grooving, after you are finished the dry groove, put it through a wet groove. It will seal those cracks and prevent expansion.

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    MasterCrafter OptiBoarder MasterCrafter's Avatar
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    Does this happen before the customer picks them up or before hand?

    The reason i ask is people like to clean their glasses with WINDEX !!

    This will crack the lenses for sure.

    If it is happening before the customer gets them... see above answers



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    OptiBoard Professional Mike Fretto's Avatar
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    These cracked lenses are returning from our outlying offices after dispensing. Still waiting to hear from someone who may have heard about the Blue-Ray disk thing . I guess I dreamed it :-)
    Mike

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    Mike, accurate sizing is typically the first thing that I would look for, but since that seems to be adressed, I would look for any type of dull cutters / wheels in your edgers as well as your groover. Are these lenses having any exposure to the types of chemicals that are taboo for poly?

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    OH, I would not put any stock in the Blu-Ray craze "no pun intended" as a reason for questionable poly quality.

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    OptiBoard Professional Mike Fretto's Avatar
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    Albednar the lenses arent exposed to harmful chemicals while in our possession, what happens to them once the patient gets their grubby little hands on them who knows. I seem to remember in the early days of poly there were some occasional carbon specks in the lenses then CD's became popular and the manufacturers of raw poly pellets had to tighten up their quality control. It would seem Blue-Rays are taking that to another level maybe the material itself is more brittle then before.
    Mike

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    You will get all kinds of advice on preventing this problem. The reason is that it is a commion, big problem. Find an alternative material and presto! The problem goes away.

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    Use sharp cutting surfaces and poof, the problem is non-existent.

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    Blue Jumper Chemical Resistance of Polycarbonate Sheets....................................

    Here is one of the most complete tables to let you know which chemicals are harmful to Poly.



    Chemical Resistance of Polycarbonate Sheets

    For chemicals and corrosive media not depicted in this list, please contact your SPS representative. They will place you in contact with SPS' R&D & and Technology Department.


    The table on the following pages uses the following key:



    R
    - Resistant
    LR


    - Limited Resistance (gradual attack over time may occur)
    N


    - Not Resistant (rapid attack or attack over short time period will occur)


    See pages at :


    http://www.palramhort.com/pdffiles/PC_Products_General_Info/PC_Chemical_Resistance.pdf

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    Optician Extraordinaire
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    I have some poly drills (I won the lenses in a drawing and they had to be poly) and one of them cracked at a drill hole within a couple of months. I sent them back to the lab for a redo. It's been 10 months and no problems since. I figure it was due to a bad drill hole as I am very careful with them and clean them with plain water most of the time. I use mild dish soap once in a while. I never used Windex.

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    Redhot Jumper Many of the labs are using now "Drillseal"....................................

    Quote Originally Posted by Happylady View Post

    I have some poly drills (I won the lenses in a drawing and they had to be poly) and one of them cracked at a drill hole within a couple of months. I sent them back to the lab for a redo. It's been 10 months and no problems since. I figure it was due to a bad drill hole as I am very careful with them and clean them with plain water most of the time. I use mild dish soap once in a while. I never used Windex.
    Many of the labs are using now "Drillseal" after drilling Poly holes. This seals all the rips made by the drilling and you will get no more cracking on rimless frames.

    Vision Ease recommends the use of this product for a trouble free life of Poly rimless frames at:

    http://www.vision-ease.com/Portals/V...lessMounts.pdf

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    OptiBoard Professional Mike Fretto's Avatar
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    Chris I was hoping to hear from you is there a distributor in the States for Drill Seal we have been using it for several years, now were told our company will no longer allow international orders.
    Mike

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    Blue Jumper No customs involved........................

    Quote Originally Posted by Mike Fretto View Post

    Chris I was hoping to hear from you is there a distributor in the States for Drill Seal we have been using it for several years, now were told our company will no longer allow international orders.
    Here it gets complicated (would love to have a distributor)....................you order and we send it in a Jiffy Bag in the mail, or larger quantities by UPS ground that gets straight to your office, as we do the customs clearing at the border, your company has nothing to do with it, just get the shipment to the door and pays for it in US $. Actually it is like getting the order from Upstate NY.

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    Quote Originally Posted by Chris Ryser View Post
    Many of the labs are using now "Drillseal" after drilling Poly holes. This seals all the rips made by the drilling and you will get no more cracking on rimless frames.

    Vision Ease recommends the use of this product for a trouble free life of Poly rimless frames at:

    http://www.vision-ease.com/Portals/V...lessMounts.pdf

    Chris, I use your Drillseal product (in fact, I used it yesterday on a drilled rimless job). Do you think it or your poly edge polish product, if applied in the groove of a poly lens with a Q-tip, would help to eliminate much of the cracking and delaminating described in this thread?

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    Manuf. Lens Surface Treatments
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    Redhot Jumper poly edge polish product, if applied in the groove of a poly lens with a Q-tip.......

    Quote Originally Posted by jefe View Post

    Chris, I use your Drillseal product (in fact, I used it yesterday on a drilled rimless job). Do you think it or your poly edge polish product, if applied in the groove of a poly lens with a Q-tip, would help to eliminate much of the cracking and delaminating described in this thread?
    jefe.................they do help to eliminate stress cracking by sealing the surfaces from rips and mechanical damage.

    However the whole surface of the bevel is an un protected area, without protection of the hard coat, that is exposed to all sorts of fumes or solvents floating by in a gaz or liquid type. These products can start a destructive reaction that will get the lens to craze.

    By sealing the surface of the bevel you will totally protect that surface from most damaging contacts and therefore fully protect it.

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    OptiBoard Professional Mike Fretto's Avatar
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    Chris, Im not sure I explained well, I have to place my orders through my home office. They wont allow any international orders any more. So I need a source in the US to order through, Ive talked to two wholesale labs I currently do some work through and their not using it. I hate when powers that be make decisions that they dont fully understand the consequences of. I guess thats just life in the US of A
    Mike

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    Quote Originally Posted by WFruit View Post
    :idea:USE TRIVEX INSTEAD:idea:
    LOL! So true.....It's a moot point if you use the best materials.

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    OptiBoard Professional Mike Fretto's Avatar
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    We grind lenses for 6 offices if I could get the dispensers in 6 offices to quit selling poly I would be a happy man, but that aint gonna happin anytime soon.
    Mike

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    Mike.................Walman has it in stock at head office, and so does Vision Ease, hope that helps.

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