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Thread: One lens axis off by 10 degrees

  1. #1
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    Angry One lens axis off by 10 degrees

    I am working through a military base and our equipment is OLD. We have been having issues with the right lens of each frame coming out 5-10 degrees off in the axis every time. I cannot identify what the issue is. I don't think it is the edger as we "upgraded" from the National Optronics 7E to the 7EX. We are using a 4Ti tracer, Nidek LM-1200 lensometer and the ancient AIT Speede blocker. We only cut polycarbonate lenses up to a -6.00 sphere and -3.00 cyl.
    We have tried calibrating the edger to see if that was the issue but it is not. Could it be the lensometer? The blocker? The tracer?
    We have had multiple people fabricate the same exact way and the results are the same.
    Any input or ideas would be helpful! Thank you!

  2. #2
    What's up? drk's Avatar
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    Is it consistently nasal or temporal rotation, or just random?

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    Always the same problem with old Indo with left lens. Before blocking the lens we compensate this with rotating each left lens in opposite direction.

  4. #4
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    Scribe a straight line across two lenses, don’t use a blocker or lensometer. Attach the lens to the block by hand and eye according to the scribed line. If the lens is still off axis then you have eliminated the lensometer and blocker as the issue.

  5. #5
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    Couple of thoughts.

    Since the decentration of the OD lens will result in the major portion of the lens being positioned towards the cutter body, the initial feed and take off of material will be more aggressive. Check your feed rates for poly setting. If the lens is a high power, try using a "thick or mega" poly setting to slow down feed rate.

    To eliminated Tracer issues, try doing just a left eye trace, run and check results

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    The chucks on a 7e edger need to be replaced on a regular interval, say every 6 months. The bearings inside do fail after use. Using your hand push (hard) inward and rotate. If you feel any grittiness your chuck is shot. This causes the cuck rotation to vary from the block rotation. Never lube this chuck as this will attract dust and cause premature failure.
    Change the blades more frequent. Your cutting poly exclusively so do not expect 500 cuts. Consider your cost per cut and you will see that sneaking a few more cuts are a poor hedge on the cost of the lens.
    Blocking pads are always suspect. Super sticky rubbery pads are the wrong way to go. I know this seam counterintuitive. I once made a device out of a torque wrench to test the pound inches necessary to twist a lens. I could never get manufacturers to issue a science to their plethora of Leap™ pad designs. The biggest fault is using a pad without a hole. Solid pads tent to roll over themselves.
    It is not uncommon to get a bad roll of pads. Change lot numbers and see if this helps. Remember there is a lens side and a block side to the pads. Never pad up blocks a head of time as they will lose their properties over time. Also, double handling is a waste and a non-value-added step. Wear gloves to avoid body oils getting on the block assembly.
    As suggested slow that puppy down. You would be amazed how much torque is happening on the rough cut. Try chucking a lens and try to rotate by hand and notice the point of failure. Avoid sharp edged lens to avoid cuts.
    It has been my experience that edging equipment never gets the maintenance that they require. Consider them a BOAT (break out another thousand). In many cases your edger cost as mush as a new car and seldom gets the care and attention your car gets. Your speaking of a 7e so I am guessing upwards of 8 years old. Probably do for a complete rail bearing change.

  7. #7
    Master OptiBoarder OptiBoard Silver Supporter lensmanmd's Avatar
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    What Chris said. More important. Change the blade frequently. 500 cuts per carbide, or 10000 per diamond is based on CR39. Throw Poly and TVX into the mix, and the lifespan will be cut by 15-20%. Do Not cheat the cuts. Many labs do, based on the material mix.
    Slow the feed rate down, but not the rotation. Slow rotation will cause the blade to bite, not shave, the lens.
    I bend light. That is what I do.

  8. #8
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    Had a similar issue and upgraded blocking pads

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