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Thread: question for lab managers....

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    question for lab managers....

    Hello everyone. I have had a rash of jobs coming back with cracks in them in the last few weeks. My first thought was stress cracks from the lenses not being sized properly. But then I started seeing it in even some grooved rimless jobs. Point being, I've seen it in metal frames, zyl frames, and rimless. Not wanting to point finger at manufacturer yet (*wink), are there any other issues I should be looking at? Could it be something as simple as cold weather? Something about the edging process?

    Thanks in advance!

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    Bad address email on file leestaniforth's Avatar
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    hi. it depends on what you mean by cracks... where abouts are they? edge or centre??. if this is happening with all lens types there must be something that is common with all the lenses.. ie the process or the equipment they are produced on. More info would be good?

    cheers:cheers:

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    They are small cracks coming in from the edges. Not all of them start at the barrel either. I have seen them even start at the edge and come in even from the 6 o'clock position.

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    Master OptiBoarder OptiBoard Gold Supporter DragonLensmanWV's Avatar
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    What types of lens material?
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    Probably made up Nawth and blanks were too cold.

    I can remember getting glass blanks in from Corning in North Carolina. We were in Houston where it was 85 degrees. Took four days for the blanks to un-freeze enough to get them out of the cartons and a full week before they could be put on the generator without shattering.

    Chip

    An before you tells me this is plastic you be talking about, plastic is sensitive to temperature too.
    Last edited by chip anderson; 02-05-2009 at 10:58 AM. Reason: Chip

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    Materials seem to be across the board. I am leanig towards the weather issue also Chip. We are getting this at more than one location. So there are 5 seperate edging machines located in 3 different labs in NE Kansas.

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    Underemployed Genius Jacqui's Avatar
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    Weather. I live in a VERY cold part of Minnesota and I've seen it here unless care is taken.

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    ATO Member HarryChiling's Avatar
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    Poly also has a tendency of cracking if exposed to isopropanol, I have seen our staff try to use alcohol to clean the lenses and they'll be fine for an hour or so then they'll start little cracks. The change in temperature will do it as well when going from extremes.
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    I posted in another forum, but we have a rash of poly lenses crack lately around the edges, and not just by the normal screw grommet location.

    Sharpstick

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    Vision Equipment OptiBoard Corporate Sponsor Leo Hadley Jr's Avatar
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    Quote Originally Posted by sharpstick777 View Post
    I posted in another forum, but we have a rash of poly lenses crack lately around the edges, and not just by the normal screw grommet location.

    Sharpstick
    So is it only poly?
    Ill bet they are being exposed to a chemical somewhere along the way.
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    Underemployed Genius Jacqui's Avatar
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    Quote Originally Posted by OpticLabRat View Post
    So is it only poly?
    Ill bet they are being exposed to a chemical somewhere along the way.
    Could be chemical. It could also be a dry cut edger with a semi-dull blade doing it. Chris Ryser and maybe others make a sealer for poly drill mounts, would using this on the edges help??

    I hate working with poly !!!!!

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    Vision Equipment OptiBoard Corporate Sponsor Leo Hadley Jr's Avatar
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    Quote Originally Posted by Jacqui View Post
    Could be chemical. It could also be a dry cut edger with a semi-dull blade doing it. Chris Ryser and maybe others make a sealer for poly drill mounts, would using this on the edges help??

    I hate working with poly !!!!!
    He mentioned above that there were 5 different edging machines. I suppose they could all be dull.
    I am still leaning toward chemical reaction.

    Years ago when I was in the corporate retail world:( there was a new product that was a chemical edge polish and or edge tint. Our pencil pushers at the home office jumped on this product and crammed it down our throats. They even forced a quota on us selling the product or face being "written up"
    This product seemed to work great until people were coming back after 30 days with edge cracks. I never seen a group of pencil pushers scurry away so fast.:D

    As Harry mentioned above, some alcohols will do the same thing and we all know what acetone will do. I suspect there is a chemical being used somewhere along the line. It could even be something in the edger bucket causing it. Lets get the Optical CSI on the case
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    Harry:

    I don't know too much about poly (other than it's definitely not my favorite lens material) but I have handled and worked with a lot of PMMA.
    I know that you can just wipe PMMA with alcohol and if viewed with a good light and magnification you will observe fine cracks. When the doctor sends you a prosthetic eye patient with a crazed conformer you can bet he put it in alcohol to "sterilize" it.
    If for some reason a patient or practioner gets the urge to sterilze a prosthesis an attempts to put it in alcohol it will craze to even begin to disintegrate depending on how long it was exposed.
    I suspect that poly may be the same albeit perhaps a bit slower.

    Chip

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    I too had about 10 jobs come in that same way about 3 weeks ago. all of mine were SV Poly with Avance. Some of these were cut at the lab for VSP jobs and some I cut. My lab has been investigating it for me.

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    ABO-AC, NCLE-AC, LDO-NV bob_f_aboc's Avatar
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    Keep in mind that a lot of labs use ultra-pure isopropanol. You might not see anything happen from a wipe with an alcohol pad, but if the trays are being held near the flammable storage area, there may be enough fumes present to cause widespread damage.

    I also agree with Jacqui about the dull edgers. I have seen this happen when lab managers get a little "thrifty." Generally, you won't see any problems at the edger. They start to creep up after delivery.

    Another question that may point to dull blades; have you noticed any off axis problems with your jobs? Dull blades pull at the lens instead of cutting cleanly. If things are regularly coming out 1-2 degrees off axis, you may have found the problem.

    My 2 cents worth.

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    Took the alcohol away from everybody on monday. Just using mix of water and dawn dishwashing liquid to clean things now. I have a feeling this might turn out to be the culprit. I appreciate all the responses, keep them coming if you have anymore ideas!

    Stay Tuned......

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    OptiBoard Professional Mauro.Airoldi's Avatar
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    Isopropanol and poly? I hardcoat poly with a coating with a good % of isopropanol.... It is not a problems (we coat 150-300 every week)
    can you post a photo of the lens with troubles?

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    Do you have any other information on this? We've had quite a few poly lenses come back from the same doctor (more than average) and I'm thinking it is because he is cleaning them with isopropanal. Are there any technical papers that discuss this or is this just common sense?

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    Honestly, this is the first time I have run into the theory that isopropyl alcohol has this effect on poly lenses. Like I said in an earlier reply, I just removed it from my processes this week so I may not have any conclusive evidence for a few weeks. I have been in this business for 20 years and one thing I have learned is never rule out anything.....lol.

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    Quote Originally Posted by OpticLabRat View Post
    So is it only poly?
    Ill bet they are being exposed to a chemical somewhere along the way.
    If it is chemical, fumes or liquids I would suggest you put the sealer on the edges, which seals permanently against such attacks.

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    It is very likely due to dull cutting surfaces. Dull blade on a dry edger or worn wheel on a wet, or a dull bit when drilling. Labs tend to stretch their blades and wheels beyond limits. All you have to do is look at the cutting surface under a high power microscope. When the cutting surface is worn or dull, it "rips" the material instead of cutting it, thereby cracking it. Kind of like ripping apart some soft cheese with a dull knife or even your fingers.

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    Quote Originally Posted by fjpod View Post
    When the cutting surface is worn or dull, it "rips" the material instead of cutting it, thereby cracking it. Kind of like ripping apart some soft cheese with a dull knife or even your fingers.
    That is correct.................Drillseal will fix the rips and cracks from drilling holes.

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    Quote Originally Posted by Chris Ryser View Post
    That is correct..................
    Why thankyou, Chris.

    So if you are finding your poly jobs cracking shortly after you dispense them, tell your lab to sharpen all the tools in their shed.

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    i got a call from the owner of the lab that i use today and he told me that he just got off the phone with the regional VP from Essilor and that he had told him that this problem is nation wide now. and that they are dong what they can to get this fixed asap.:hammer:go figure, well off i go to continue to bang my head against the wall

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    Quote Originally Posted by jb@kso View Post
    Took the alcohol away from everybody on monday. Just using mix of water and dawn dishwashing liquid to clean things now.
    How are going to get the layout markings off with Dawn???

    BTW, I use denatured alcohol from the paint stripper section. Is that wrong? Stressful on AR?

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