troubleshooting tips

Better Bevels

by Karlen McLean, ABOC, NCLC

With the proliferation of lens bevel styles, it's becoming increasingly more challenging for eyecare practitioners and labs to ensure the best bevel results.

Complex bevels are necessary in order to effectively fit lenses securely and aesthetically in the vast array of today's frame designs.

We consulted with Pech Optical, based in Sioux City, Iowa, for beveling insights from Kathryn Gross-Edelman, director of education; Karen Stotz, quality assurance technician; and Kevin Wilmes, research and development manager.

Pech Optical reports that the key to better quality eyewear resides not only in machines and machining, but in research and quality assurance. In an effort to explore the subject, the laboratory's research and quality assurance departments began an endeavor to bring to the forefront the metamorphoses of bevels. The goal was to create a database with all the identified frame/bevel configurations entering the lab finishing department today.

Q How can I stay on top of all the new bevels and best be able to work with them?

A To date, 37 different bevel configurations fill Pech's bevel library. Identifying and understanding the construction of the plethora of bevels is paramount to dispensing the premium eyewear that consumers are demanding. Educating dispensers can only happen when labs are able to identify and construct the bevels necessary for lenses to stay in the frame.

Pech Optical explored many methods, which led to the birth of Pech Putty. By applying this putty into the frame bevel area and removing it, identification of the bevel is possible.

While machines hold the key to better quality eyewear, Pech has identified nine different bevel designs made possible with a 5-axis edger. The library of variations of those nine bevel designs continues to grow every day as the company receives new frame styles. Frame designs and materials today may dictate special lens materials needed to complete safe and cosmetically pleasing eyewear.

Understanding bevels can help ensure that lenses fit better in frames and are more secure in their settings. Shown above, Pech Optical's bevel reference card

Q What frame problems can an improper bevel cause and how can I avoid causing them?

A Many times a dispenser feels ill-fitting lenses only mean a wrong C-size, when in fact the wrong bevel is placed on the lens. The lens will not fit down into the bevel, causing the eyewire to roll and the lenses to snap out of the frame. Reordering another pair of lenses will not remedy the situation.

An improper bevel will cause undue stress on the frame as well as the lenses. Chipped frame finishes, compression marks on lenses, and broken parts are all results of wrong bevels.

A goal for the best cosmetic effect on Rx lenses involves matching the base curve of the frame with the base curve of the lens to give lenses a "plano look." This can be accomplished only with a 5-axis edger.

Q When doing a bevel for a wrap frame, what is the best protocol?

A The number-one protocol for a wrap frame is a 5-axis edger with a CAD technician to support the machine. Only a technician with CAD knowledge and experience can truly work the edger to its full potential.

An incline bevel is necessary to reduce the problem with splayed temples and end pieces. The 5-axis edger places a bevel on the same plane as the lens being edged as opposed to a standard edger, where the bevel and the excess lens thickness is left at a 90-degree angle. A lens with a true incline bevel allows the frame to relax around the bevel and reduces the problem of splayed temples. Incline bevels are paramount to maintaining wrap frame alignment. EB