EYE ON EQUIPMENT

Finishing Sun

Sun lens edging tips that will boost your customer service and increase second-pair sales

Q: WHAT ARE THE BEST TECHNIQUES FOR EDGING POLARIZED LENSES?

a: In polarized lenses that use the film or the “wafer” layering process, the lenses are clear and it’s the polarizing film that gives them their color. As a result, the lens portion in front of the film and behind it is transparent.

When edging, adjust the location of the bevel closer to the lens front to help hide this area within the frame eyewire, if possible. Additionally, using a matching tint to the lens edge by using color/tint pens can help cover this clear edge. It can be risky to tint them due to the heat (200° to 210° F) and potential for delamination of the lens.

Caution is important when working with polycarbonate or any polarized lens as they tend to be more expensive. You always want to be sure your machine is correctly calibrated prior to edging these lenses. Polarized polycarbonate has the laminate film across the front of the lens surface, whereas plastic or high-index lenses have the film about one millimeter under the front of the lens surface.

Pro Tips:

BLOCKER

Only use good quality lens blocking adhesive pads to avoid slippage. Always verify proper axis alignment on the lens and on the blocker to ensure proper axis alignment of the polarization film layer.

EDGER

Maintain proper sharpness of edging wheels/blades. Dull wheels can cause axis problems due to slipping on the block and can introduce excessive heat to the edge of the lens, causing delamination of the polarized film layer.

FRAME SELECTION

Be realistic in frame selection and always pre-fit the frame prior to taking measurements. Pay particular attention to nose pad design and placement. Often the lens will protrude behind the eyewire, especially on higher prescriptions, and will interfere with the nose pads or actually hit the patient’s face. Even though modern equipment makes it easier to edge difficult prescriptions into wrap frames, that doesn’t mean it will be the best choice optically or cosmetically for the patient.

LENS MATERIAL

Although polycarbonate is often chosen for its impact resistance, it can be more prone to delamination and clear spots on the edge due to the bevel being placed behind the polarized filter layer. CR-39 and high index can easily be tinted in these situations, often creating a more cosmetically appealing pair of glasses.

PAL TROUBLE

If all printed marks have been wiped off of a dark lens, the use of a PAL Identifier renders the task of locating the laser markings easier.

Additionally, it’s really important to be sure that you use good pads to ensure you don’t have slippage or incorrect chuck pressure, which will throw off your axis and cause issues with how the polarization film blocks out the light.

— Matt Menzies, technical director/product manager, Briot/Visionix USA

Q: WHAT CONSIDERATIONS NEED TO BE GIVEN TO THE BEVEL PLACEMENT WHEN EDGING SUN LENSES FOR HIGHER WRAP FRAMES?

a: Whenever possible with wrap frames, use an edger that is capable of applying a step bevel on the backside of the lens. This will allow the bevel to be placed further to the front, preventing possible clear spots on the edges of the lens caused by the bevel being placed behind the polarized filter layer.

A step bevel also allows lenses to be inserted into the frame more easily and prevents the lens from easily popping out of the frame when flexed.

If the prescription does not allow the bevel to be placed on the front of the lens, sometimes an edge color treatment or tint can be applied after edging to minimize the appearance of a clear spot caused by the bevel being placed behind the polarized filter layer.

Proper size is also critical to prevent stress marks and delamination of the polarized filter of the lens due to oversized lens size.

— Matt Brown, senior sales support, Coburn Technologies

Q: WHAT KIND OF EQUIPMENT IS BEST SUITED FOR FINISHING SUNWEAR?

a: Dark lenses can certainly be a challenge. My advice would be to look for a blocker that has a feature with a camera layout. The illumination automatically adjusts for the user, making it very easy and user friendly.

I advise buying an edger that allows you to do either a roll-back bevel or a step-back bevel. With either of these features you’ll have the ability to control the amount of roll- or step-back bevel at different points of the lens.

By investing in technology, you will be able to produce a better looking and more precise fit to justify a premium price that your customer will be satisfied with. Also with these tools, it will allow you to offer a wider range of prescriptions in a sunglass frame.

— Matt Vulich, vice president, marketing, AIT Industries