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Thread: Poly cracking... What's up?

  1. #1
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    Poly cracking... What's up?

    Within the past year or so I have seen repeated pairs of specs with poly lenses cracking. We've dispensed poly for years, however, this past year a crazy amount of lenses have been cracked.

    So, my question is: Is anyone else seeing this issue surface?

    I have to believe that it is a substrate issue. Has something changed in the raw material of poly?

    Collective wisdom please.

    Jamie

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    I've read the posts on the link you provided, however, I can't believe that all the sudden my in house lab and all of the wholesale labs we use have dull cutting surfaces on the equipment nor can I believe that it is an alcohol issue.

    I agree that these (dull cutting surfaces or alcohol) can cause these problems, but has all of our industry's labs' edgers blades become dull this past year or perhaps they have all of the sudden began using alcohol to clean lenses. I can't buy that premise.

    The cracks are occuring not just in the cold weather but summer also. It's happening on SV, D-segs, PAL's, all designs. The cracks are starting just about anywhere on the lens edge not just at the barrels.

    Something is up with the substrate. Hmmm?

    Still looking for answers.

    Jamie

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    Chi-Com Plastic.

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    not just here?

    We also have seen an unidentifiable increase in cracked poly, and we have been near 90% poly fitting for 5 years. As well as I know poly from manufacturing through dispensing, I also am surprised. New Poly materila supplier, manufacturing coating process?
    denny

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    Chip,

    Are you suggesting that the raw poly material that lens casters are using is of low quality and that is the problem?

    Couldn't quite understand your post.

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    Read up on Chi-Com sheet rock. Don't expect thier plastics are of any higher quality. Their vaccines aren't either.

    Chip

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    Thanks Chip that helps. I thought that was where you were going with that.

    Something has occured withing this past year and your suggestion has merit. I guess the question now is to our lens manufacturers.

    So, lens manufacturers, have you begun using a different raw material supplier/s? Help us understand the "why" part of this equation.

    Not that I'm lovin poly or anything, but, Trivex sure seems a better alternative in the absence of answers from our manufacturers.

  9. #9
    Master OptiBoarder OptiBoard Gold Supporter DragonLensmanWV's Avatar
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    Quote Originally Posted by Jamie Brady View Post
    Thanks Chip that helps. I thought that was where you were going with that.

    Something has occured withing this past year and your suggestion has merit. I guess the question now is to our lens manufacturers.

    So, lens manufacturers, have you begun using a different raw material supplier/s? Help us understand the "why" part of this equation.

    Not that I'm lovin poly or anything, but, Trivex sure seems a better alternative in the absence of answers from our manufacturers.

    I think Trivex is a better answer, PERIOD!:cheers:
    DragonlensmanWV N.A.O.L.
    "There is nothing patriotic about hating your government or pretending you can hate your government but love your country."

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    Dragon -- I agree, however, I'm lookin for answers.

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    ***Uilleann to the General Forum Please***

    Quote Originally Posted by Jamie Brady View Post
    Dragon -- I agree, however, I'm lookin for answers.

    My pal Uilleann should be around soon. He knows all of the ANSWERS when it comes to polycarbonate!!!

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    Underemployed Genius Jacqui's Avatar
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    I think they should outlaw polyc--p.
    Proud Member of the ABE Club!
    Don't feed the Beast...

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    ABO-AC, NCLE-AC, LDO-NV bob_f_aboc's Avatar
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    2 1/2 hours this thread has been up and no Chris Ryser???

    Is he OK?
    A lack of planning on your part DOES NOT constitute an emergency on mine!

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    Is it November yet? Jana Lewis's Avatar
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    Quote Originally Posted by bob_f_aboc View Post
    2 1/2 hours this thread has been up and no Chris Ryser???

    Is he OK?

    *snicker* :cheers:
    Jana Lewis
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    OptiWizard OptiBoard Bronze Supporter pezfaerie's Avatar
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    We are experiencing the same problem with cracking poly and have tried changing everything about the edging process to no avail. Within a month the pt's back with splits and cracks. I hope you find out some good info!

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    Are there any other reasons not to ue poly. Guaranteed solution to your problem: quit using poly.

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    I recently tried to show a new kid in our industry how poly was bulletproof. I took a brand name poly stock lens out of the package, put it on the bench and slammed it with a hammer.

    The lens shattered all over the tech bay!!!

    It seems some companies are using some kind of poly blends. I would assume its for better optics, but they sure are not bulletproof anymore.
    I did however find some other poly lenses and they took a .45 caliber hit with only a big dent.
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    Master OptiBoarder OptiBoard Gold Supporter DragonLensmanWV's Avatar
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    I've only had problems with surfaced poly lately. Haven't had much problem with stock poly. I mostly use Polycore for my stock poly lens.
    DragonlensmanWV N.A.O.L.
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    Poly cracking, material change, dull drills or alcohol involved ?

    What has come out of this ?
    Has it calmed down i.e. were really all drill bits in the US dull at the same time, suggest you go after them..... ;-)

    However if OpticLabRat's hammer test is typical, in the US there is a potential problem. Anybody submitted a Poly to a FDA test recently ?
    More facts would be helpful.
    In Europe we do find during edging differences in PC material coming from different sources, but we don't need to pass an FDA.

    I have come across bargain CR39 lenses without UV absorbers added, they transmitted UV down to about 310nm and will go yellow and brittle when exposed to sunlight over time. Similar thing could be happening here.

    Georg Mayer
    Rodenstock-Munich

  20. #20
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    Redhot Jumper Vision Ease has recommended.................

    Vision Ease has recommended the use of "DRILLSEAL" in the drill holes to seal off rips and cracks on Poly lenses which will prevent cracking from the holes out with great success.


    Vision-Ease Lens, Inc.
    TECHNICAL SERVICES DEPARTMENT
    TECHNICAL TIP





    EDGING:
    Edge lens to desired shape and size.
    Safety bevel both sides of lens after rimless edging procedures.•


    Edge polishing and tinting should be done prior to drilling.•


    Drill lenses prior to anti-reflection coating.



    MANUAL LAYOUT:
    Mark horizontal axis/ 180-degree line on each lens with a water-soluble pen; duplicate pattern axis line if no

    prescription axis is applicable.

    •


    With a felt-tip pen, carefully place a dot at each drilling location on the lens front and verify correct positioning.

    •


    Location should be double- checked for accuracy to +/-0.5mm.



    DRILLING:
    Polycarbonate cuts best with a sharp burr operated at low speed and minimal to moderate pressure. Twist

    style drills, cutting less aggressively, often leave subsurface damage.
    •


    Place lens with front towards drill bit and slowly operate drill through lens; back drill bit out of hole often to

    remove cutting debris that will increase heat damage.
    •


    Be sure to chamfer around the hole when finished drilling. (Much like safety beveling after edging)•


    Note that excessive pressures and speed create damaging heat, which may create eventual fractures.•


    An extra precautionary step to avoid fractures would be to place a drop of OMS Drillseal into the hole.


    Distribute the Drillseal evenly with a toothpick. This will seal the hole and it dries instantly.


    Please note the

    dropper may gel if left in the bottle.





    CLEAN-UP:
    Cleaning should be done prior to mounting with warm soapy water with a clean water rinse.•


    Wiping should be minimized to avoid abrasion from cutting debris.



    MOUNTING:
    Assemble lenses with appropriate hardware, minimizing excess tension.•


    Frames should be fully aligned and formed to lens prior to final assembly.•


    Excess stress on assembled eyewear may eventually create fractures. Use of plastic bushings is

    recommended.




    INSPECTION:
    • Mounted lenses should be inspected for excess stress, correct positioning, and alignment.

    Chris Ryser
    ________________________________________
    DLO. NA.IC.I.T.PO

    http://optochemicals.com............................. http://arcoatings.com

  21. #21
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    My company pulled all of our spray cleaner, we think that is what is causing it. We have tried switch poly brands but that didn't work. We should start noticing a difference in the the coming months.......hopefully.

  22. #22
    Manuf. Lens Surface Treatments
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    Redhot Jumper Enough of it touching the bevel periodically will do the trick ......

    Quote Originally Posted by regional_manager View Post
    My company pulled all of our spray cleaner, we think that is what is causing it. We have tried switch poly brands but that didn't work. We should start noticing a difference in the the coming months.......hopefully.
    Polycarbonate is what it says. Changing brands will not help as the chemical formula is the same for everybody.

    The edges are not protected by the hard coat, and most lens cleaners contain between 20 + 30% ISP (Isopropyl Alcohol). Enough of it touching the bevel periodically will do the trick to start a destructive action.

    You can always put a sealer coat on the edges.
    Chris Ryser
    ________________________________________
    DLO. NA.IC.I.T.PO

    http://optochemicals.com............................. http://arcoatings.com

  23. #23
    Master OptiBoarder mike.elmes's Avatar
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    Two things cause cracks on poly on a regular basis in our shop....1. Locktite on screw/nuts

    2. screws and nuts....nut tightened too tight.

    I refuse to sell poly in rimless unless its a plug mount, and I can't get Trivex. PERIOD.

    I do however see many chains and or discounters using poly as its cheap...
    Many similar problems with scracks around drill holes where nuts are overtightened, or some unknowing Optician/ lab tech administers Locktite.

  24. #24
    Master OptiBoarder OptiBoard Gold Supporter DragonLensmanWV's Avatar
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    Just for giggles, when I came back from vacation on Monday, I edged a poly lens and a trivex lens, inscribed a P and a T on them with a diamond scriber and put them in a jar and filled it with the 99% isopropyl I use to clean the lenses before coating.

    So far, no damage to either one. Let's see how long it takes.
    DragonlensmanWV N.A.O.L.
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  25. #25
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    Dragon:

    At last grass roots real world research!
    Bravo!

    Chip

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