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Thread: surfacing - question for lab managers

  1. #26
    Master OptiBoarder Jeff Trail's Avatar
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    One other possibility to mention and I saw it no where in the post, but would you be possibly using an MR3 coater or mini? I went into a lab about a month ago and they were having tons of issues..first told me power and than when they sent me some samples I was locating tons of aberrations off center... called and asked them to check powers coming right off the line BEFORE coating.. and tada..it was the backside coater...had them dip the lens in heated distilled water in the tint unit and the "power problem" was solved....
    If it is a "lap" issue you should be seeing a pattern to the lens powers vs.. index ... if you did than you could always just run a compensation chart to set you cross/base and tools or just let the compensated tool bring it in...more chance of swirls/waves if you do not compensate both cut and tool though.. sometimes spending a lot to solve a little can be corrected with a "free" work around..
    Poor guys answer to buying laps in 6ths..or even 10ths...
    Just a thought of something I did not see mentioned.....

    Jeff T.

  2. #27
    Master OptiBoarder Darryl Meister's Avatar
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    Our Prodigal Son has returned! What's it been, Jeff, a year or two?!?

    Best regards,
    Darryl
    Darryl J. Meister, ABOM

  3. #28
    Objection! OptiBoard Gold Supporter shanbaum's Avatar
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    I thought we were doing the Time Warp again...

  4. #29
    ATO Member HarryChiling's Avatar
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    Robert "The Too Master" Shanbaum, heck it beats being called a "tool".

  5. #30
    Master OptiBoarder Jeff Trail's Avatar
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    tool? been called worse.. and truthfully probably lived up to the label ...

    Darryl, I still read postings about every day but it has gotten was to political and cut throat on here at times to make it worth while to reply, our old debates between all of us, even when political had a little more restraint and a bit of respect, agree to disagree type posts, even the optical postings have gotten a little more down and dirty and insulting...big difference in my book between being passionate vs.. condescending ... I think I'll start tinkering in the ophthalmic section... leave the rest to the guys still full of spit and vinegar..:shiner:

    Jeff "grind'em if ya got'em" Trail

  6. #31
    Master OptiBoarder Darryl Meister's Avatar
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    Jeff, We generally get a little classier clientele in this particular forum. I mean, for people who drink cheap beer, anyway.

    Best regards,
    Darryl
    Darryl J. Meister, ABOM

  7. #32
    RETIRED JRS's Avatar
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    Greeting Jeff. Been awhile and I hear ya.

    Take care
    J. R. Smith


  8. #33
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    Quote Originally Posted by shanbaum View Post
    thanks for the thread.. Frankly, i didn't cath a lot, because of my english and ability to not understand it well :(

    Thank you for your posts, it help me a lot, but in some topics i am somehow in the dark so I have a few questions that i would like to know:

    1. We use the tooling index 1.498, tool step 0.125
    therefore, the strange thing for me is, that this tool step is only for CR39.

    I try to explain it on example:

    TOOL STEP for 1.5 index material TOOL STEP for 1.6 index material
    SPH CYL SPH CYL
    -4.00 0 -4.00 0
    -4.00 -0.12
    -4.00 -0.25 -4.00 -0.25
    -4.00 -0.37
    -4.00 -0.5 -4.00 -0.5

    So that means that tools differ at steps for cylindrical power (at 1.6 at 0.12D, at 1.5 at 0.25D), but steps in spherical power are the same -0.25.
    We use calculation program for SATISLOH - rXpert.

    Could somebody explain it how it is possible that cylindrical step of tools differs between materials 1.5 and 1.6 if the same tooling index is used ?

    2. If the tool index 1.498 is used for 1.67 material, the power off errors is about +/-0.84D. When i did any calculation in rX program, i was able to see not bigger deviance like +/-0.0625D. Because in the rXprogram i can see the "real" curve or tool and rounded curve or tool.
    How should i understand the theoretical deviance +/-0.84D at 1.67 material with 1.498 tooling index ?

    3. Tools compensation - Does it work like this ? if i have tool of SPH:-9.00 ; CYL -9.75 i should be able to measure the -9.03 ; CYL -9.78.. Am i right ?
    does it rule for all tools and is there any connection with lens thickness ?

  9. #34
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    Quote Originally Posted by Jeff Trail View Post
    One other possibility to mention and I saw it no where in the post, but would you be possibly using an MR3 coater or mini? I went into a lab about a month ago and they were having tons of issues..first told me power and than when they sent me some samples I was locating tons of aberrations off center... called and asked them to check powers coming right off the line BEFORE coating.. and tada..it was the backside coater...had them dip the lens in heated distilled water in the tint unit and the "power problem" was solved....
    WE use the mr3 coater, but we have power off problems before we use coating machine. Maybe the problems with power off causes the ultrasonic cleaner that is ordered after production hall. I will check it.

    Quote Originally Posted by Jeff Trail View Post
    If it is a "lap" issue you should be seeing a pattern to the lens powers vs.. index ... if you did than you could always just run a compensation chart to set you cross/base and tools or just let the compensated tool bring it in...more chance of swirls/waves if you do not compensate both cut and tool though.. sometimes spending a lot to solve a little can be corrected with a "free" work around..
    Poor guys answer to buying laps in 6ths..or even 10ths...
    Just a thought of something I did not see mentioned.....

    Jeff T.
    I believe that problem lies in front curves with combination to lap tools. Could you have a look at my previous message in this thread - point 3 ?
    Where can i find the pattern to lens powers vs index ?
    how to work with compensation chart ? Like that - the used lap tool was SPH -1.00, CYL -1.50, and result power was -0.02 out of tolerance, so i set there for used lap tool compensation 0.02 ?

  10. #35
    Master OptiBoarder Jeff Trail's Avatar
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    You most likely will have to go in and see how your surface program is picking compensated tool curve selection.. you maybe able to refine the round off point where it either goes up or down when selecting a tool that falls "inbetween" ...running 12ths on a 1.67 index will be a nightmare in both sphere or spher/cyl. combination .. just due to what the curve (base/cross) will do to how much effective power you end up with...
    Take for instance you if your program is rounding tools and you are running a cr39..the curve you need falls between and the program rounds it "up" a 12th...what you need is -7.41 and it gives you a tool of - 7.50 in CR39 you come out say a 12^ off.. no big deal... but say the program is not taking into consideration the effect of tool compensation and it rounds off the same way... it jumps to being a .25^ to a .37^ off ... your program possibly is not taking into account the curve vs. index and resultant power as it should... if you can not change the compensation does it give you a choice of tool curve? ie., 6ths 10ths ?? you could always run that "seldom run job" under the compensated and than you know which way to go, up or down on your actual 12th tools.. remembering curve vs. final power is multipled by the index of the material

    as far as a compensated chart... you could basically set of a statistical chart and show what tools were picked and the resultant power.. it would not take long to see a pattern of how much it was off based on power vs. tool ..if it is all the same material you'll be able to build you a working compensated chart... it is not going to be exact as running tools in 10th 1.67 or 6ths as you should with 1.74 but it would keep you in the ball park..

    I feel for you, it is a small percentage of your production but an expensive mistake and make it hard to dicide to "over invest" to correct the few or live with the frustration... or there is always the answer of routing it out to a secondary lab set up for this and you get the lens uncut and just do the edging.. no or little profit vs. inhouse but no breakage loss and frustration

    Jeff "grind em till the scream" Trail

  11. #36
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    Jeff,

    I am so glad to see you posting!
    Thank you for sharing your knowledge and experience with us!

  12. #37
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    Confused Confusion on Polishing machines---any difference between polshing machine& smoothing

    Hi Guys!
    I just got 2 used coburn 5000 cylinder machines.
    Unfortunately one which i used for polishing developed fault,i switched over and started using the smoothing machine for polishing but the lenses come out with waves.
    I need help to resolve this.
    I will also like to know if their is any difference between a smoothing machine and a polishing machine.
    Thirdly,what is the recommended speed,pressure, and time for polishing cr.39 lenses.
    I look forward to your kind help.
    Regards
    Okafor

  13. #38
    Master OptiBoarder Jeff Trail's Avatar
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    you can also set "stroke" as well, waves are going to be either pressure or heat, to much pressure causes friction (heat) ...make sure that the polish is hitting the lap and not just spraying over the top and off ... that layer of ploish between pad and lens is as important as just spraying polish everywhere ... I would get a gauge to actually check head pressure, depending on the dials is a no no... make sure you have even pins, make sure the polish is flowing where it needs to, check the clamp pressure or down pin pressure, ... do NOT run it on high, you are going to most likely increase the wave issue... also check the stroke length of the head to table... if it was going from a finer to polisher, the head pressure is probably to high ... I was always amazed how people turned up pin pressure and cut cycle times trying to compensate and save a little time.. I have seen them set so high it was shoving the axis pins back out :-)

    I would start with the basics and make sure the nozzle is set correctly spraying the polish, than move to testing the pin pressure... you may also want to make sure that the wobble assembly is right and you are getting the right motion, another thing that can generate unwanted heat.. check your polish temps as well..

    I can not remember the exact head pressure, it has been a very long time since I ran rockets.. keeping these Toro's running to speed would drive anyone to drink... I am sure someone can rattle off the # for you ....

    Jeff " time to play Sherlock Holmes" Trail

  14. #39
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    I have questions about lap tools tolerance..

    Which tolerance do you use for lap tools? For example lap tool of +2.00.. I measure +2.05 and i'm not sure how to set up the range of tolerance. I know that the smaller tolerance the better power results..
    I would like to know the tolerance you use

  15. #40
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    use a sag guage instead of a diopter guage, much more accurate.

    Sag tolerance: +/- 0.02 mm of sag results in +/- 0.031 diopters.

    Also, when cutting (if you are using a mechanical lap cutter instead of a generator), after you've hogged the excess material off, use a last cut taking about 1/10th of a mm off, and slow the sweep speed down so you get a very smooth surface. Irregular surfaces will transfer to the pad and can result in uneven fining.

    Your off tolerance could be from a variety of factors, but it is usually because your pad thickness hasn't been taken into account. How that is done depends on the type of lap cutter you are using.

  16. #41
    Master OptiBoarder Darryl Meister's Avatar
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    use a sag guage instead of a diopter guage, much more accurate
    Just keep in mind that all of these instruments actually measure sagitta; any gauge or instrument that reads off in diopters is just converting a sag value into a dioptric reading by assuming a tooling index. And, to a "first order" approximation at least, sag values and diopters are directly proportional to each other.

    Best regards,
    Darryl
    Darryl J. Meister, ABOM

  17. #42
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    Quote Originally Posted by Darryl Meister View Post
    Just keep in mind that all of these instruments actually measure sagitta; any gauge or instrument that reads off in diopters is just converting a sag value into a dioptric reading by assuming a tooling index. And, to a "first order" approximation at least, sag values and diopters are directly proportional to each other.

    Best regards,
    Darryl
    True, but most of the diopter guages I've seen don't have much in the way of resolution, which is why I prefer a direct reading sag guage. I've got three: two analog (dial type) that read to 0.01 mm with 50 mm round bars (no ball ends) (one for plus and one for minus), and one digital that reads to 0.001 mm. The digital is used to read base curve sags on all lenses, the analog for plus is to read tool curves and the analog minus is to read lens curves. We used to have another plus/minus set with 35 mm bars, but since plastics have taken over much of the high minus work, we converted them to other uses.

    It's also important to check your sag guages from time to time with a master lens of a known curve or saggita depth. Guages out of calibration will mess not only with your head but also your end results.

  18. #43
    Master OptiBoarder Darryl Meister's Avatar
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    If you have access to a Younger Gauge Master, it has some calibration curves that you can use for calibrating many bar gauges, but not bell gauges. RH Burton (RH Burton), now National Ophthalmics, was distributing these for a while, although I'm not certain whether they still offer them. I imagine that some of the lab machinery or lab consumable companies out there will offer some different tools for checking the calibration of sag gauges as well.

    As for establishing tolerances, this ultimately boils down to controlling the propagation of errors. Power errors are incurred by errors in curvature of the front surface, errors in lens thickness, and errors in curvature of the back surface. The front surface can be off by up to 0.09 D according to ISO manufacturing tolerances. And the lens thickness can be off by up to 0.3 mm according to the ANSI Z80.1 standard.

    For the back surface curvature, your lap tools introduce randomly distributed rounding errors equal to one-half of the lap tooling increments or less. And any error due to the curvature of the lap tool will either increase or decrease the final error. Consequently, the increments of your lap tools should be a factor in this decision. For instance, compared to eighth-diopter tooling, a tenth-diopter tool can be off by an additional +/-0.0125 D without exceeding the same potential rounding error of an eighth-diopter tool.

    Best regards,
    Darryl
    Darryl J. Meister, ABOM

  19. #44
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    Esseng, contact Chris Bowers a member on optiboard. He has a great excel sheet for simulating rounding errors on different tooling index and tooling steps and shows you also how many tools you will need, maybe he can help you.

  20. #45
    Master OptiBoarder Darryl Meister's Avatar
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    Yes, the refractive index of the actual material is also an important factor. For eighth-diopter tooling, the rounding error ranges from +/-0.059 D for hard resin to +/-0.087 D for 1.74 high-index. For tenth-diopter tooling, on the other hand, the rounding error ranges from only +/-0.047 D to +/-0.070 D.

    Best regards,
    Darryl
    Darryl J. Meister, ABOM

  21. #46
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    The Tool is on optiboard, you can find it in this threed:

    http://www.optiboard.com/forums/show...906#post297906

  22. #47
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    I can make glass curve masters if anyone needs them, we have master curve plates that are tracable back to nat'l standards. Let me know if you are interested.

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