EDGING HIGH BASE CURVE EYEWEAR

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New high base curve eyewear designs present special challenges that modern lens edging equipment can overcome.

Beveling eyeglass lenses has always been challenging but newer high base curve eyewear designs present special challenges. The reason is from having to create a bevel on the lens in a configuration that enables it to fit snugly into the groove (known as the frame’s bezel) of a frame. On flatter minus lenses, that can be easy but on lenses with high base curves, it can be seriously frustrating. Modern lens edging equipment has overcome the myriad problems by developing features that handle the job handily.

Ed De Gennaro is Director, Professional Content of First Vision Media Group.

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The frame in this illustration is a high base curve wrap frame designed for sunglasses. Its nearly 20Ëš of wrap will make inserting lenses challenging. One reason why a steeply curved lens is difficult to secure into a metal or plastic eyewire or eyerim is because of the way the lens is held in place. The eyewire (eyerim) exerts a circumferential force around the lens to hold it in place. Since the lens is bulging forward, this pressure tends to push the lens forward, making it unstable. If a lens is beveled using conventional means, the angle of the bevel on the lens will not match the angle inside the frame unless the frame designer has specifically addressed this issue. That’s why it’s important to use proper frames and edging equipment for high base curve edging. Edger systems with wrap-capable tracers are recommended. Most equipment manufacturers have developed tracers that can trace a high base curve frame and accurately record the angle of the lens bezel and its depth. These data are used by compatible edgers to create the right bevel configuration for the lens going into the frame.
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Many edger systems have edging options specifically for high base curve lenses that provide the right beveling configurations for most high base eyewear jobs. For those with special requirements, some edger systems have additional controls the operator can select and adjust to obtain the ideal outcome. If produced properly, inserting high base curve lenses should be no more difficult than inserting any other lenses. For high base curved eyewear, the outcome is worth the additional effort.

 

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