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Thread: HELP SWIRL MARKS IN CR-39 FT's

  1. #1
    Bad address email on file APV Optical's Avatar
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    HELP SWIRL MARKS IN CR-39 FT's

    Any one with suggestions. Most of my work consist of specialty, Trivex, Polarized, Poly, anything but the norm. We just had a new account get on board, however they are one of our only uncut accounts, meaning, here come the cr-39 ft-28's by the ton, which Im not complaining but the craziest thing happens. Upon inspection 9 times out of 10 the lenses have swirl marks and have to be re ran. This happens with lenses that we use our own llaps with. What we have been doing is making foam laps when we re-run them and they come out great. Now you would think Humm maybe the laps need to be re-trued. but it is happening to often only on theses lenses. All and seriously all of the others are coming out fantastic. This is all powers not just high cyls or prism. Even -.50 sph. Its really got me stumped and I have been swamped so its just easier to say just make a tool and we will figure it out" but this is adding up. Thanks in advance for any help

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    Forever Liz's Dad Steve Machol's Avatar
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    Maybe it's the fining pads and polish. What are you using?


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    RETIRED JRS's Avatar
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    Or an aggresive Poly formulated polish. Or both. Or no filtration and he's picking up hairlines that he would not notice in Poly or Trivex.
    J. R. Smith


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    Jeweled Eyewear Billy Brock's Avatar
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    had the same thing happen back in the old days with cr-39 ......... one time contamination in our slurry ......... one time defect polish from mfgr

    this blows my mind that a new lap solves your problem ? ? ? .......hope you find the solution quickly.... be sure to post the results


    B

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    Master OptiBoarder Jeff Trail's Avatar
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    Chris,


    I would agree with JR and Steve, you have to do an elimination of factors here.. you are not using the same pads for all those materials are you? If you are the grit for poly and trivex are more agressive than for CR39.. You can use the same type of slurry (polish) but you need to check and see if the polish you are using is for a combination of all these materials.
    Also you may need to check your air pressure and run time on the cylinder machines... one way to give it a "quick check" is when you load up the cylinder machine with a pair of CR39 lens run it for about 15 seconds and than pull them back off and see how the lens looks.. within that 15 seconds you should have gotten a nearly uniform smoothing out of generator marks..they will be light but you should be able to see if it is smoothing it out across the lens as it should.
    The poly and trivex (poly more so) is the harder stuff to do, CR39 is the "easy stuff" :) ....
    1) check your pads ..the pads you are running are probably to agressive for cr39.. cr 39 should be around a 600 grit.
    2) check your run time and air pressure on the cylinder machine
    You think it might be because you are making a foam tool and re-running it, I would tend to think it is just because you are re-running it that the swirls are being removed.

    Swirls usually are in a lens because, one the run time and air pressure is incorrect. Two, the wrong pads are used. Three polish is broken down, but that is more a "frosting" type look than major orange peel.

    Are you using a one step system or two in your cylinder machines? I would start there and take a good look at the pad grit.

    Here is what I run. First fine 600 grit at 1:10 18 pds. pressure. 2 nd fine 9 mic. blue for 1:10 18 pds. pressure. 3:45 for polish and it is polish FOR cr39/high index..

    You can elimanate your generator or you would have power problems across the board, you can eliminate the cylinder machine being short stroked or off axis or all your stuff would be coming out incorrect or hit and miss.. I would take a good look at the grit of the pads and the polish if it were me.. :)


    Jeff "gee usually it's the spectralite giving people fits" Trail

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    Bad address email on file APV Optical's Avatar
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    Thanks for all the replies. For cr-39 I am using p-1200 honeyfine brown one step pads. The polish is for hard resin, high index and poly. My fining for cr-39 is 2:45 secs with 18 psi then 4:00 polish. I have some older pads we use to use. One step they are red ptr-767?? Anyway I will try those today....(fingers crossed) Thanks again...

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    RETIRED JRS's Avatar
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    There are much better 1-step pads available than a 1200 Brown. The 1200 brown was a 2nd fine poly pad - if memory serves.

    Try the yellow and orange striped pads - from PSI, DAC, etc.
    J. R. Smith


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    I had this problem many years ago when I first started doing CR.
    Since you mentioned when you change the lap the problem disappears I will share what it was in my situation.

    Look for dings on the edge of the lap. It is amazing how many dings occur on the edge of the tool. This little ding created a raised spot on the edge of the lap. When the lens went over this spot I got swirls. I found that this was what was causing the problem. No more swirls for the last 15 years.

    Jerry

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    opti-tipster harry a saake's Avatar
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    Lightbulb polishing

    back years ago when i was in the labs with B&L, we had an automatic cribber made by coburn. After the lense came out of the generator, they would be cribbed down as needed, and then be put on the fining and polishing machines.
    .....While i have also seen that same problem happen that jerry alluded to, cribbing the lenses down seemed to work pretty good and i wonder if its used today.

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    Master OptiBoarder Jeff Trail's Avatar
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    Jerry,

    Since Chris had no problem running the poly's and the Tr-vex with these tools than I would think it is not the "tools" but in the process with the pads or polish :)

    Harry,

    Instead of crimping I always prefer to just set the stroke on the cylinder machine, a lot of people have no idea that this can actually be done.. it saves the cylinder machine wear and tear and makes the job come out better, I have one set up for short cycle strokes 70 mm and smaller and one set up for the largest stroke cycle I run all my over size and PAL's on..

    One other thing that could be causing the problem is that the cylinder machine is slightly out of calibration, the more agressive grit pads for poly and tri-vex are eating it up where you would not notice but in a cr39 where you have a different run time and pin pressure this could be a big problem.. I would double check and make sure that the heads are lined up and on center with a set of cyl. blocks.
    I'm still leaning towards the pads or polish or a combination of both as being the culprit.
    Gee it is usually the other way around poly's and tri-vex being the pain not cr39 :)

    Jeff "boy it can be frustrating when it does not come out" Trail

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    Bad address email on file Susan Henault's Avatar
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    I have a few questions for the lab experts, just for my own knowledge. Does the application of a backside hard coat reduce (or render invisible) the appearance of minor surface imperfections? Also, do labs generally inspect the surface quality before or after (or both) the scratch coat application (for the lens materials that require it). I know that I am risking coming off like a dumb bunny, but I really want to know. Is it possible for a larger scale swirl problem to go unnoticed, because things slip by after the application of backside hard coating?

    Please ... go easy on me ... ;)

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    RETIRED JRS's Avatar
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    Susan, (hello btw) putting a backside coating on scratched lenses usually hides little. Extremely light marks - sometimes.

    The bigger problem can come later if the lenses are AR'ed. Minor, or almost non-visable (to the eye) marks will show up when the AR is applied. Depressions, grooves, pits, raised spots, etc. all tend to rear up and become visible after the AR process. It is usually a waste of materials/labor to hide issues under a backside coating used to mask the real problem.

    Now, that said - there are techniques in use for using a backside coating instead of polishing. The normal process for this does not use the typical fining process. Some methods use very smooth cutting from a generator (or similar device), others use a series of fining pads. Polishing (and sometimes fining) are skipped, and the lenses are coated. These processes have some limitations in either materials and/or rear curves.

    If you are interested in seeing some of this "stuff" - call me when we're at VE-W and I'll walk around with you. If you don't mind, that is.
    Last edited by JRS; 07-28-2003 at 07:13 PM.
    J. R. Smith


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    Jeff
    The reason I brought up the tools having burrs and eliminated the other problems was that he stated when he changed to a foam lap the problem went away. That would seem to eliminate pads and polish.

    Harry, I happen to now have the ability to crib on the generator and I crib and pin bevel everything. It makes everything easier. slows down the generating a little but regain the time in the finish department by not having to edge as much off. It also cuts down on twists.

    Everyone has their own little system that they use. If my curves are not toatally fined in in 15 seconds my generator curve isn't as good as it should be.

    My first fine and my second fine is at 1.30. My polish is at 4 minutes. I have my pressure at the finer at 14 pounds. My pressure at the polisher is 12 pounds. I run all materials but Trivex and Poly this way. There is never a problem.

    I increase the pressure to 18 pounds for Trivex and Poly. The first fine is 1.30 and the second is 2 minutes. I polish these for 6 minutes.

    I also prefer an 8 leaf pad. My second fine is a 3 micron. Since I run 50 per cent a hi-index of some type I find that the 3 Micron pad works best for me.

    As far strokes I have one stroke setting and that is where it stays except on an extremely high minus that causes trouble which is rare. Maybe once every couple of months.

    Like I said everybody does it a little different and what works great for one may not work may not work great for the next.

    Jerry

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    RETIRED JRS's Avatar
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    Jerry, your times and pressures are very good. Most people want to INCREASE pressure, but you know better.

    The summary on 'burrs' is also very valid. It could well be something as simple as badly managed tools (laps). We do have a tendency to over dramatize these situations.

    PS - I think you could probably not increase pressure on Trivex and Poly, and still do quality.
    J. R. Smith


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    We notice a similar problem when our gripper pads are wearing at the edges. For some reason, the CR39 is the first material that is effected. New pads eliminate the problem. If you are using gripper pads, you could look at that as a possible cause.

    shutterbug

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    Master OptiBoarder Jeff Trail's Avatar
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    JR & Jerry,

    Nice to see other people actually change air pressure and run times according to material!! :) ..This drives me CRAZY, I have been in one lab "fixing" cylinder machines and "trying" to show the tech the problems..the complaint is the lens is picking up waves... and all three times I went in they have the pins set at 30 pounds...that's right 30lbs!! and the run time is 2 minutes on the first and second fine... I'll turn it down and try to explain with that much pressure you are generating a TON of heat as well as that long you are picking up every imperfection in the tool to compound the problem even further.. the tech turns it right back up after I leave says the same thing "well that is the way I learned to do it" ...gee you would think they would get tired of paying me $45 an hour to keep coming back and telling them the same thing over and over...
    You know thinking about it, it could be that the problem shutterbug mentioned as well and the reason the re-running is working on a foam block is they are applying a new pad :) .. I hope Chris is looking at everyones post and doing some elimination to get to the problem..BTW further up the thread I also prefer Dac's striped pad system as well...

    Susan,

    No one can ever ask a "dumb bunny" question :) .. this is the stuff we lab rats thrive on :) .. JR answered your questions about the marks and swirls but I'll answer about inspection... most often the higher the amount of production the less inspection is done.. usually it's checking powers.. and if they are using a digital analyzer than things like swirls or waves can be passed a long without being found... it depends on the lab usually and how they go about checking.. all my guys visually check for waves before popping them onto the lensometer, and the person doing the deblocking I have a light set up with a dark background and as they deblock and wash the lens off they are in the habit of holding the lens up and checking for any scratches or swirls and waves before moving over to the final check of power.. mainly it's for saving time and the guys doing the deblocking can spot if we have a problem right than and trace back to where the problem might be...most often, wrong tools, polish etc., etc.
    It still amazes me that some labs just do not look at the big picture and shove things through and forget that each account looks at it as THIER work is all they care about.. you push slop through and waste a day or so shipping than they get the lens and have to call and reorder, the account is usually not to thrilled :)
    I'll not claim that a "bad" lens sneaks through ever so often but I have about the best inspection system I can think of and three different people doing the checking so one may miss but all three? not very often.. Quality control should be a very important part of the process, but sometimes that is not as important as "prices" in todays market.. you want them cheap as possible but still perfect? .. those two things do not always work well together in every lab :)

    Jeff "gee us lab rats just love to tinker" Trail

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    Bad address email on file APV Optical's Avatar
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    Im taking everything in. We tried different pads, not the problem, to remark on the post above, The 1000 brown are for poly 2nd fine, not the 1200 brown. I did see Jeff you said a lab you go into will run lenses too long. I just recently changed our fining time to 2:45 secs. That could be the problem. We will try and go back to 2:min . Hopefully wew can report good results. Thanks everyone

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    Bad address email on file Susan Henault's Avatar
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    You guys are great, thanks for the responses!

    When it comes to combating price issues with my 3O customers, I always go to bat for the labs (also my customers). I often fall back on a saying that I learned way back in my Sola Technical Service days:

    "We can do it FAST, we can do it WELL and we can do it CHEAP ... pick two"

  19. #19
    Bad address email on file APV Optical's Avatar
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    I tried using a yellow second fine pad after the one step pad yesterday everything came out great..hmmmm With my coburn 5004 cylinder machines I never had this problem, the problem was spectralite, now with the new cylinder machines (acuity) powers are great, but now I have to use a two step system with cr-39.. Is this uncommon. Anyway thanks again and hope this thread has come to a happy ending

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    OptiBoardaholic
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    We use gripper pad system and one step fine, its all great! Loh generator and cylinder machine ( Loh calls it a smoother/polisher).
    Joseph Felker
    AllentownOptical.com

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    Polishing Pads

    Anyone using yellow polishing pads? Ihave noticed no imperfections when generating or fining, but the orangepeel does come up AFTER polishing. I have heard that there can bedust(YES DUST) particles in the polishing pads. I don't think theyfabricate these yellow polishing pads in a "cleanroom".


    LEONARD OPTICAL
    Last edited by leonardoptical; 02-04-2005 at 12:17 PM. Reason: Spacing is not coming out correctly on words

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