IT’S A WRAP
Shape reproduction of lenses in steeply curved frames is a three-dimensional challenge for the ECP.
Today’s discerning patients with money to spend are looking for prescription lenses in the stylish, new, highly wrapped frames being marketed by high-end designer and sport frame suppliers. If you aren’t able to match the exact base curve of the original plano lenses that came with the frame, you will want to make sure the equipment you are using can match the beveling curvature of the original lens.
SYSTEMS TO CONSIDER
New stylus-free shape recognition features found on systems like the Perception from Briot USA can determine the exact beveling curve required to match the frame curve in the X, Y, and Z axes. It does this by placing a demo lens in a virtual cube that maps it similarly to the way corneal mapping machines do. This makes it possible to edge the lenses so the frame is not flattened when the lenses are inserted.
When it comes to getting factory-perfect sizing on a wrapped acetate, nylon, or composite frame, there are two additional factors that come into play. The first is the depth of the frame bezel (groove), and the second is the backside lip coming off that bezel. Most wrapped plastic frames have a sizeable lip on the back that requires a special type of shaping called “shelf beveling,” “step beveling,” or “T beveling.”
Finishing systems that have stylus tracers are well suited to determine the three-dimensional shape of the lenses and the depth of the frame bezel. If your edging system does not have shelf beveling capabilities, you will be doing quite a lot of hand edging. The problem with this technique is that it creates an unsightly frosted ring around the lens circumference.
On systems such as the Briot Alta Zd and the WECO E.6 from AIT Industries, Inc., shelf beveling is accomplished with the use of a small accessory finishing wheel deployed off the built-in accessory arm to hone out a backside shelf bevel. Santinelli International, Inc.’s ME-1200 3D Drilling Lens Edger grinds the front and back of the lens bevel independently, with both its High Curve Auto Preset and High Curve Custom Mode functions. In Essilor Instruments USA’s Mr. Blue 2.0, the finishing wheel is integrated on the GMD module to create the shelf bevel.
Optek International’s Optek Shape finishing system basically mills the required bevel using technology similar to what’s used in free-form surfacing, while the shelf bevel on Coburn Technologies, Inc.’s HPE-8000 features a specially designed and angled full-size wheel.
Systems manufactured by National Optronics were among the first true milling edgers to have the ability to do perfect wrapped beveling. The company’s flagship edger, the 7Ex, can also drill and notch lenses wherever needed for stylish frames.
Wraparound frames provide a number of advantages over their flatter counterparts, including side impact protection, panoramic view, and wind and dry eye protection, not to mention their stylish look. If you learn how to handle them in the lab, they can be a nice source of additional income and prestige for your shop.
Michael Frandsen is the owner of Quality Performance Ophthalmic, Inc., a custom service optical laboratory in South Jordan, UT.
WHERE TO FIND IT:
A.I.T. Industries, Inc. (Weco) 800-729-1959 • aitindustries.com
Brain Power, Inc. (BPI) 800-225-5274 • callbpi.com
Briot USA 800-292-7468 • briotusa.com
Coburn Technologies, Inc. 800-262-8761 • coburntechnologies.com
Essilor Instruments USA 855-EZ-FINISH • essilorinstrumentsusa.com
National Optronics 800-866-5640 • nationaloptronics.com
Optek International 727-522-2301 • optekinternational.com
Santinelli International, Inc. 800-644-3343 • santinelli.com