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Thread: Surfacing Troubleshooting

  1. #26
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    Not at all, thanks for taking the time to provide your expertise on my issue.

    Quote Originally Posted by Darryl Meister View Post
    This may have already been mentioned in one of the above posts, and I apologize in advance if this post is redundant, but you may be able to tell the source of the "scratches" by inspecting the actual pattern and texture of the scratches.

    Generator marks that have not completely fined out will have a more consistent pattern (spirals for a 3-axis generator, parallel curves for a 2-axis generator) and are more "sleek." Random and more jagged scratches or "swirls" would be more indicative of contaminated water or slurry during fining or polishing.
    My 1st issue (hairline circular scratches) I'm puzzling over as I haven't seen such a pattern before, they are not swirls nor are they random. They are also extremely faint and only visible under the reflection of an arc lamp, you can only see them if you look directly at the lens while reflecting the light of the lamp off the lens.

    My 2nd issue (scratches and sometimes swirls on perimeter of lenses) seems pretty commonplace, most likely due to lack of cribbing and chamfering of the lens blank. They are also only visible when the lens is held perpendicular to under an arc lamp.


    My 3rd issue (imprint? of a fining or polishing pad) I haven't seen this type of defect before, the imprint is only visible under the same conditions as the 1st conditions but at a different angle. The imprint seems to be made up of tiny hairline scratches.

    So lucky me, all 3 of my issues has to do with scratches, but in my opinion none of them are generator marks. I can try to get some better images, maybe bring in a better camera or something if anything thinks it will help.


    Quote Originally Posted by Darryl Meister View Post
    If you haven't already done this, inspecting the lens surface carefully under an arc lamp or in a shadow box between each step of the process might also help you isolate the source of the scratches. And, of course, obvious issues, such as tears in polishing pads.
    Pardon my ignorance, but what and how exactly do you use a shadow box? I did a little google-fu and found that a shadow box is a wall mounted mirror (or a box of makeup)? I can imagine how it's used but my google-fu didn't really help me much on shadow box usage. Unfortunately no obvious issues such as tears in fining pads or polishing pads, nor did I find anything which I would consider significant in my filtration.

    Quote Originally Posted by Darryl Meister View Post
    I have seen several very good recommendations above regarding cribbing and chamfering the lens blank to improve water and slurry flow. Remember that over-polishing to work around this issue, in addition to reducing throughput, can lead to other unwanted problems, such as waves and polishing burn.

    Best regards,
    Darryl
    I am actually a little excited about going into work Monday, I have all these recommendations to try out! I will update the thread with my findings as soon as possible! Thanks!

  2. #27
    Master OptiBoarder Darryl Meister's Avatar
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    Pardon my ignorance, but what and how exactly do you use a shadow box?
    The device may go by different names. I've always known ours as a "shadow box" or a "shadow scope." It is basically a bright lamp, I believe with some sort of collimating lens, which is used to illuminate a lens under inspection while it is held over a matte white screen. Common surfacing defects in the lens show up on the screen as faint shadows.

    My 1st issue (hairline circular scratches)
    I noticed these in your first photo, which is why I brought this up. Several suggestions pertained to contaminated water or slurry, although I wouldn't have expected this kind of pattern due to the more complex movement of a cylinder machine head. But, in all fairness, I haven't done any lens surfacing in years.

    I would consider any stages in your process that might involve rotational movement or contact against a rotating part. For instance, since you're using a 3-axis generator, I imagine that they could be generator marks. If so, you should detect these marks on the lens surface after the first fine.

    Even something as simple as cleaning the uncoated lens surface with a circular wiping motion may be the cause.

    Best regards,
    Darryl
    Darryl J. Meister, ABOM

  3. #28
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    Quote Originally Posted by Darryl Meister View Post
    The device may go by different names. I've always known ours as a "shadow box" or a "shadow scope." It is basically a bright lamp, I believe with some sort of collimating lens, which is used to illuminate a lens under inspection while it is held over a matte white screen. Common surfacing defects in the lens show up on the screen as faint shadows.
    Ah, so a shadow box/shadow scope is the same thing as an arc lamp? We have a Bulbtronic, basically an arc lamp which shines onto a flat platform so you can hold a lens parallel to the platform and see the shadows, so I think we're talking about one and the same. This makes me curious as to what the hell this thing is then; http://www.veatchinstruments.com/pro...?ic=CPCO06-000.

    Quote Originally Posted by Darryl Meister View Post
    I noticed these in your first photo, which is why I brought this up. Several suggestions pertained to contaminated water or slurry, although I wouldn't have expected this kind of pattern due to the more complex movement of a cylinder machine head. But, in all fairness, I haven't done any lens surfacing in years.

    I would consider any stages in your process that might involve rotational movement or contact against a rotating part. For instance, since you're using a 3-axis generator, I imagine that they could be generator marks. If so, you should detect these marks on the lens surface after the first fine.

    Even something as simple as cleaning the uncoated lens surface with a circular wiping motion may be the cause.

    Best regards,
    Darryl
    Yes, now that I think more about, the cylinder head has a much more complex movement than just a circular motion, and the hairline circular scratches in my 1st picture are just that, just very faint scratches about 1mm long going into a circle. I've gotten so many recommendations to check our handling/cleaning of lenses that I'm getting very paranoid. I might even just start having people rinse the lens and then blow them off with an airgun or something...
    Last edited by IChen; 06-16-2012 at 09:22 PM. Reason: Link

  4. #29
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    @IChen:

    The article that you were wondering about in Post #28 is a mirror used in a refracting lane. The mirror is usually front-side "silvered", and is adjustable at all corners in order to reflect a projected chart image for viewing.

  5. #30
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    Quote Originally Posted by uncut View Post
    @IChen:

    The article that you were wondering about in Post #28 is a mirror used in a refracting lane. The mirror is usually front-side "silvered", and is adjustable at all corners in order to reflect a projected chart image for viewing.
    Oh wow, I just realized, a projected eye chart screen. Duh. Well guys, good example of my uhhh...airheadedness? I'm not sure of the word I'm looking for but you can go ahead and fill in the blank for me, thanks.

  6. #31
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    Welcome to the Forum, IChen. No need to feel airheaded.........we all are a-learnin' as we go in life.................and we all have those "DOOH! moments. I wish you success in finding the source of the circular scratches.

    I assume that they are on the back side of the lens?
    Are there any airborne sources of polycarb dust/swarf with in the room?(Just thinkin' out loud)

  7. #32
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    Yeah I understand too, I can totally understand a couple of "DOH!" moments but when you're getting several a day, something's wrong and you start feeling not too bright. Also it's more like relearning, I've been taught it, I just don't remember it until someone points it out or smacks me in the face with it.

    Quote Originally Posted by uncut View Post
    Welcome to the Forum, IChen. No need to feel airheaded.........we all are a-learnin' as we go in life.................and we all have those "DOOH! moments. I wish you success in finding the source of the circular scratches.

    I assume that they are on the back side of the lens?
    Are there any airborne sources of polycarb dust/swarf with in the room?(Just thinkin' out loud)
    Yes, you're assumption is correct they are only on the back side of the lens. The only 2 sources of polycarb dust/swarf becoming airborne would be the generator (which has a working vacuum system) and also the vacuum system for the generator which is unfortunately in the same room, so if the filter on the vacuum isn't on right or clogged I guess it could be shooting some stuff into the air. I would think I would notice if it was putting stuff into the air as I kinda stuck my face in the exhaust when I was getting it set up to make sure it wasn't. I also put a bag over the exhaust while we did a couple of jobs to double check but I didn't find anything in the bag so I think we're good.

  8. #33
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    FWIW, I use recirculated water in my finer. We change it out every 10-15 jobs or so, but I really don't see that it makes too much difference in results. If anything, water with a lot of lens material in it just acts likes more of an abrasive...but I still recommend changing it out.

    We have at times not put safety bevels on lenses and saw no difference in results, but again, I recommend it.

    Cribbing on the other hand, does show improved results in that lenses finish faster and the perimeter of the lenses come out better.

    I still think those hairline scratches look like they are from toweling the lens.

  9. #34
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    Thanks a lot for your input, I'll be testing out some of the recommendations made in this thread and it definitely helps to have someone else's results to compare against. Unfortunately I won't be able to do anything with cribbing until we get that fluted cutter in so I'll just have to work around that for now. The hairline scratches I'll verify tomorrow if it is due to handling and report my findings as soon as possible.

  10. #35
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    Sorry about not updating yesterday, got called away from the lab. Today I only got to play with 1 job and the option available/chosen was lighter pressure and it doesn't look like I'll have much time to try anything else for the timing being. Anyways, onto my results.

    Machine was flushed and water replaced with fresh water, slurry is used but stirred before use. Lens was rinsed and air dried and examined between each step.

    1st Fine: P280 for 2 minutes @ 16psi on high, stock removal of 0.164mm
    2nd Fine: 15um Optifilm for 2 minutes @ 16psi on high, stock removal of 0.016mm
    Polish: Clearly Digital (3300G from PSI) + Maize HD Polish Pad from PSI, 6 minutes @ 16psi on high, stock removal of 0.016mm

    Results were better than initial results posted but all 3 issues are still present. The amount of hairline scratches have been reduced but there are still present and still in the same pattern as reported earlier (circular). The scratches and swirls on the perimeter of the lens have been reduced, but still present as well. And finally the imprint of a pad is still faintly visible, but much harder to see.

    So from this job I think it is safe to conclude that the hairline scratches are not handling scratches nor are they coming from the water. The slurry was only used for 3 jobs before this, so unlikely, but still a possibility for some sort of contamination.

    And for the benefit of anyone unfamiliar with my 2nd step; http://www.1-800-optisource.com/1-St...ge-Stripe.aspx.

    Also this pad can be used for one step fining of CR-39 (I use a compensated version for this), I use it for 2 minutes @ 19.8psi on high followed by 6 minutes polish with the same conditions and no issues with CR, so polycarb is the only material (I only do CR and poly anyways) which these issues present themselves in.

  11. #36
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    Quote Originally Posted by IChen View Post
    Sorry about not updating yesterday, got called away from the lab. Today I only got to play with 1 job and the option available/chosen was lighter pressure and it doesn't look like I'll have much time to try anything else for the timing being. Anyways, onto my results.

    Machine was flushed and water replaced with fresh water, slurry is used but stirred before use. Lens was rinsed and air dried and examined between each step.

    1st Fine: P280 for 2 minutes @ 16psi on high, stock removal of 0.164mm
    2nd Fine: 15um Optifilm for 2 minutes @ 16psi on high, stock removal of 0.016mm
    Polish: Clearly Digital (3300G from PSI) + Maize HD Polish Pad from PSI, 6 minutes @ 16psi on high, stock removal of 0.016mm

    Results were better than initial results posted but all 3 issues are still present. The amount of hairline scratches have been reduced but there are still present and still in the same pattern as reported earlier (circular). The scratches and swirls on the perimeter of the lens have been reduced, but still present as well. And finally the imprint of a pad is still faintly visible, but much harder to see.

    So from this job I think it is safe to conclude that the hairline scratches are not handling scratches nor are they coming from the water. The slurry was only used for 3 jobs before this, so unlikely, but still a possibility for some sort of contamination.

    And for the benefit of anyone unfamiliar with my 2nd step; http://www.1-800-optisource.com/1-St...ge-Stripe.aspx.

    Also this pad can be used for one step fining of CR-39 (I use a compensated version for this), I use it for 2 minutes @ 19.8psi on high followed by 6 minutes polish with the same conditions and no issues with CR, so polycarb is the only material (I only do CR and poly anyways) which these issues present themselves in.
    Call PSI. Ask them for samples of their Black/Brown first and second fine pads for poly. Tell them your problem and that a satisfied PSI customer recommended that you call.

  12. #37
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    IS there a trick to balancing and "re-belting" an Accuity cyl. Machine??? We had a leak under one or both spindles and when gaskets were replaced and gear pulleys placed under newly gasketed spindles the belt keeps riding up <(quickly). Any wisdom?

  13. #38
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    Quote Originally Posted by LLano View Post
    IS there a trick to balancing and "re-belting" an Accuity cyl. Machine??? We had a leak under one or both spindles and when gaskets were replaced and gear pulleys placed under newly gasketed spindles the belt keeps riding up <(quickly). Any wisdom?
    A little late but there are some set screws that go into the gear to hold it in place.


    As for OP. I hope you have solve your problem by now but I would suggest you check the curves of your generated lens to make sure it's cutting true and also check the curves on your laps

  14. #39
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    It has been a while since I have been on OptiBoard and this problem immediately caught my eye. I have read through all the posts and everyone offers great suggestions. I would like to share my personal experience with the 2 step pad combo you are currently using. I believe that the 15 micron orange stripe pad is not nearly aggressive enough to effectively smooth the surface coming off of a P280 first step. I would suggest trying something a bit less aggressive on your first step such as a P400. It is still quite aggressive, but will leave a better finish for the 2nd step to do its job more effectively. My recommendation for your second step would be more in line with a pad such as a P1000 or P1200.

    All of your other surface parameters look right where they need to be.

  15. #40
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    Over half a year, I always told myself if I made an account I wouldn't abandon threads, not enough discipline apparently. Sorry guys .
    A long overdue update, the scratches and fining marks on the rim of the lenses was fixed by swapping to some aluminum laps, it seems the plastic ones we were using were either not true or had some sag (either one possibly due to age).
    The hairline scratches and the pad imprint were due to the polishing pad. Once we swapped over to a higher quality polishing pad (Pink Supreme or 549-7) the issue was resolved. I suspect this is due to thickness of the polishing pads as well as the nature of the felt (which determines how the polish particles are held).

    With the issue resolved, I'd like to give my thanks to those who gave their inputs and those who read my thread. Sorry about abandoning thread, hopefully this post will be a step towards making it up to you guys.
    Thanks again.
    Last edited by IChen; 02-19-2013 at 01:52 PM. Reason: Grammer >.<

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