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Thread: size of a blocking ring

  1. #1
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    size of a blocking ring

    How blocking rings are being picked up ? - i mean for lenses in general, not special lenses and sunglasses.
    I was taught to use as big as possible (because of better support from bottom to avoid surface deformations), but recently, i have heard an another theory.
    Could someone bring more light into this topic ?

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    My company (again, working glass), uses two sizes:

    for plano production: standard 47 mm coburn ring with sintered metal blocks with 158 metal

    for Rx production: cast-in-place 50 mm full block with 117 metal.

    Generally speaking, the larger the blocking surface the less surface deformation you get in the surfacing procedures (generating, fining, polishing).

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    OptiBoardaholic other_bill_fea's Avatar
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    We have a number of blocking rings from 48-68mm that we use. Which one depends on the Rx, but the software picks as large of a ring as it can for the given job. As you said, the more support (especially for free-form) the better.
    FEA Industries
    Independent Wholesale Optical Lab
    www.feaind.com
    www.optmagazine.com
    Morton, PA

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    Quote Originally Posted by other_bill_fea View Post
    We have a number of blocking rings from 48-68mm that we use. Which one depends on the Rx, but the software picks as large of a ring as it can for the given job. As you said, the more support (especially for free-form) the better.
    This.

  5. #5
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    You would also want to take into account lens cribbing ,specially in high plus Rx for thickness optimization ,in this case you would like to have a smaller blocking ring so you can cribb the lens as small as posible ,depending on frame size too.

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    OptiBoard Apprentice rmnrdi's Avatar
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    We're using CC systems and I'm finding a lot of jobs that are cribbed to a 65 but the software puts them on a 53 block. Not sure what's going on there and CC isn't really giving us an answer.

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