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Thread: Too much time on my hands...

  1. #1
    That Boy Ain't Right Blake's Avatar
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    Too much time on my hands...

    I've been trying to figure this one out, so I figured I'd ask the experts...

    I've got a Coburn thickness gauge that we used to use with I think 63mm alloy blocks. It's the kind where you set the dial to the front curve and lower a plunger to the center of the lens and the dial reads the thickness of the lens.
    We're using Step One blocks (wax blocking) now. The gauge works fine for 6 base lenses (gray blocks), but there seems to be an offset of about .3mm for every diopter difference. For example, if I measure a 5 base lens and add .3 to the reading, I get the thickness called for on the job ticket (using Innovations on SGX).
    Anyone else encountered this?


    Blake

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    Master OptiBoarder Joann Raytar's Avatar
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    Is this after calibrating it with the plano block?

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    Objection! OptiBoard Gold Supporter shanbaum's Avatar
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    The gauge you're using is probably designed to work with a block that is theoretically 50.0mm in diameter. I say "theoretically" because the aluminum blocks you were using, while 63mm in diameter, actually hold a lens of the curvature specified on the block at the same position above the block's reference surface (the flat surface that snugs up against the face of the chuck) as a ring 50.0mm in diameter and 9.0mm tall would hold it. If the lens is not exactly the curve specified on the block, the thickness produced will be incorrect. Innovations deals with this by using data in a "block chart" that contains the actual dimensions of the block it selects to figure out exactly where the lens is sitting, relative to the reference surface.

    The "diopter" side of your gauge is nothing more than a 50mm sag gauge - just like the "diopter" side of the thickness-setting apparatus on an old-style generator (112, 113, etc).

    Using a Step One block, which is 60mm in diameter, simply requires a different diopter scale; such a gauge is available from your friendly Gerber Coburn representative.

    You can set up your Innovations software to provide a modified thickness setting for old-style generators (or gauges) by setting the "Calibration Ring Diameter" to 50mm. Your system is probably already set up to use a Step One block chart, from which it gets the actual dimensions, so it can figure out the difference, and adjust the "set" thickness appropriately.

    That doesn't affect the operation of the SGX, as it always receives the actual ring diameter and height along with the "true" thickness settings.

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    Master OptiBoarder OptiBoard Silver Supporter Jubilee's Avatar
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    Speaking of Thickness...

    Something I have been noticing of late using Innovations is troubles with edge thickness..

    We have had several plus lenses that center thickness will come out to exactly or maybe even .1 less than called for by the RX ticket.. but when edged to the frame, Edge thickness is too thick, in some cases coming out to as much as 3.0 for dress thickness. Frame measurements have been correct in all, except the one job today where the B measurement was actually 5mm larger than specified on ticket. This is happening in poly and hi-index 1.56 full frame and in grooved styles, but doesn't happen in every plus lens either...I haven't detected any pattern as far as power range, seen it in as low as a +1.50 and as high as a +8.00 all lense styles.

    I realize that maybe there is one or more constants that may have been keyed in wrong when Innovations was set up for our company.. but I would really like a way to determine quickly if CT is calling for the right range or not, someother way than to wait for 1st inspection and line up the frame.. mark the edge where the thinnest point should be and measure..like something I can double check before I generate it.

    With it being insurance week and all, I would really like to avoid redoing jobs....

    Cassandra

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    RETIRED JRS's Avatar
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    Are you tracing the frames - or just entering a A/B/ED on those jobs?

    I'm sure Robert will explain.
    J. R. Smith


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    That Boy Ain't Right Blake's Avatar
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    Thanks for the info. I'll see about getting a new gauge. It's nothing urgent. I may even try changing the calibration ring diameter in Innovations - the lab manager's out of town!
    :bbg:

    Cassandra,

    We've been having the same problem with plus lenses having too much edge thickness. The generator doesn't get any tracing information, just A, B and ED. Maybe that has something to do with it.


    Blake

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    Objection! OptiBoard Gold Supporter shanbaum's Avatar
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    The most common ways to end up with excessive edge thickness - assuming that that center thickness comes out correct - are 1) supplying incorrect frame measurements, and 2) using different measurements when laying out for finishing than were provided in the first place.

    There's no question that you'll get better results when a tracing is available, even if you provide accurate measurements, simply because the tracing provides vastly more information. And of course, the fact is, if you give ten opticians the same frame to measure, you'll get twelve different measurements back (and that's not to criticize opticians; frames are just really hard to measure accurately with a ruler, especially the E.D.).

    It sounds to me as though you need to contact your tech services department - if there are configuration settings that need to be changed (there certainly are some that affect thickness), or if some other procedures need to be refined, they're the ones who need to do that.

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    Master OptiBoarder OptiBoard Silver Supporter Jubilee's Avatar
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    Edge thickness

    So far as I said only one frame involved had incorrect measurements, and it was actually larger than what was on the sheet.

    I have reported this to our support center and well they just tell me to track it and when I get a couple of weeks of info in they will review it and look into it.. Which is what they said oh 6 months ago or so when I first had issues with it.. Now the issue seems to be even more prevalent than before with it affecting a couple of orders a day or more....

    About a third of our frames have stored "library" traces and the rest we measure and then trace when setting up for edging. The tracer is on its own system with the edgers..

    Cassandra

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    RETIRED JRS's Avatar
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    Robert - does it sound to you like they are tracing AFTER data entry, not as part of DE? "the tracer is on its own system with the edgers" seems post entry to me.


    PS to Blake - the generator could care less about the shape - traced or not. It is only looking for blocked base curve (tbc or psuedo), a CT, and perhaps a crib size. It does not calculate a CT or ET from a shape.
    J. R. Smith


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    Master OptiBoarder OptiBoard Silver Supporter Jubilee's Avatar
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    Frame measurements are entered in at time of sale..but a true trace doesn't occur till post entry.

    I definitely understand that if a 63ED was entered but it was only 60.. then sure CT will be calculated to be thicker to allow more material to be able to make it to the edge..

    Yet only one measurement was off by more than 1 mm. And on that one the ED and B were larger.. therefore I should have had too thin lenses..not too thick.

    Maybe if I can get Blake and Ken to track it as well..and talk to all the other stores in our regions, maybe we can get enough info that support can do something about it...

    Cassandra

  11. #11
    OptiBoardaholic
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    A couple of points:

    First, NOT ALL SOFTWARE IS THE SAME. Some software calculates better finished thicknesses. You must also make good use of the programs system customization or constants. You should be able to set up different finished thicknesses and grinding allowances for different materials.
    Customize these settings for the problem areas.

    Second, the axis of the ED plays an important roll in the thickness. The frame trace should definitely be done before data input.
    Joseph Felker
    AllentownOptical.com

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    Objection! OptiBoard Gold Supporter shanbaum's Avatar
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    While I would certainly agree that "not all software is the same", one should expect very similar results with regard to curves and thickness from any of the widely used packages, at least in cases of lenses with spherical fronts, as everyone calculates these in pretty much the same manner. In fact, we ran some comparative tests (though this was a number of years ago now) amongst several systems and found this to be the case.

    As I said, better results are obtained when a tracing is available, but when the tracing is done is irrelevant if the tracer is not connected to the software!

    Actually, I take that back - if a tracing were to be done prior to data entry, and the summary measurements made visible, at least those measurements could be entered. That would also ensure that the finish layout the system calculates would be what's actually used - which is at least as important as the dimensions themselves.
    Last edited by shanbaum; 12-31-2003 at 08:55 AM.

  13. #13
    RETIRED JRS's Avatar
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    Yes, I agree Robert – if they trace first (even though it is not interfaced), they could use the values returned for data entry. It would be easy enough to evaluate differences by running the job using their current method, against entering the tracing results. There could be several areas that not being considered –
    1) ED discrepancies causing thickness errors
    2) Changes in finish layout after calculation and surfacing, which places the lens in a new final location

    I would venture to guess that Cassandra is measuring the ‘ED’ by placing a ruler diagonal across the frame. This method does not give an accurate ‘ED’ unless the frame is round or oval (ovals and rounds ED being very close to 'A'). The heavier the plus power, the more important a solid set of values.

    I think Cassandra mentioned they are using Innovations. Although I’m not as detailed on Innovations as I am with CMSI (BRC/VisionStar), DVI, Optivision, and Optifacts… it seems there are some setting that could influence results - something along the line of “ED Factors & Defaults” in Innovations. Is it possible those are incorrectly set?

    Jofelk – you are correct in stating that the axis can play a roll in the resulting calculations. However, as Robert mentioned… all things being equal, almost all of the software packages product fairly equal results (spherical). I have seen some rather bizarre results when we start talking aspheric though (lol).
    Some systems make use of enough fields at data entry to capture a decent set of dimensional data (3 radii/angles + A & B) - others do not (single ED which is divided almost equally). Wrong use produces wrong results.


    Some years back I wrote a 3 page article on “ED’s” for Optical World magazine. I still do an ABO course on this subject once in awhile. And I include an abbreviated discussion on it during the ELU (Pete Hanlin has mentioned ELU on OB before). It continues to be problematic when personnel manually measure and then do not get what they expected.
    J. R. Smith


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    Master OptiBoarder OptiBoard Silver Supporter Jubilee's Avatar
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    What I will do the next time I have an issue.. is to edit the frame info in Innovations to match the trace and see what thickness it calculates. After I get several of these, I will let you know the results.


    Thanks for your help guys!

    Cassandra

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    Yes you will need to use difference chucks each time you do different base curves while using the wax blocker
    i believe for 6 base you will use the grey chucks for 5 base you will use blue chucks and so on so forth.
    the highest chuck will be a gold clored one that can accomodate between 9 to 10 base cuves.

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