Hands On: EYE ON EQUIPMENT
Tips for Edging Poly and Trivex
by Karlen Cole McLean, ABOM, NCLC, and Susan P. Tarrant

Children's eyewear, safety lenses, Duty to Warn, rimless eyewear. All are good reasons to recommend impact-resistant polycarbonate and Trivex lenses. While some ECPs remain nervous about edging these materials, today's equipment advances make it simple and successful.

Trivex lenses (top) offer safety in everyday wear, as does poly (shown below: Vision-Ease Lenses)

PROCESSING POLY

Polycarbonate is a softer material than regular plastic, and older, conventional diamond edgers may find poly's "softness" too much of a challenge. However, modern edging systems incorporate routers designed specifically for the material. Any "all-material edger" will be able to handle poly without error.

Semi-finished and finished polycarbonate lenses usually come with a scratch coating. This addresses another concern that was prevalent in poly's early years--its vulnerability to scratches during processing.

Here are some standard to-do's that will help you make the most out of poly lenses.

1. Use a patternless edger with a wet-dry cutting cycle and a draining system that automatically cleans the edging chamber.

2. A dry, ultra-abrasive wheel combined with more torque or pressure is required at the roughing stage.

3. Use an edger designed to handle poly lenses. Poly edgers rotate lens and wheel in opposing directions for better results.

4. The incorrect amount of weight on a poly lens can cause warping or craze the coating. Regularly calibrate your machine.

5. A built-in edge polish cycle replaces manual polishing and automatically corrects the "stutter marks" left on poly by dry-cut edging.

6. When drilling poly, go slowly. Drill only .5mm, back out the bit, allow the material to cool for a few seconds, and then drill another .5mm and so on until the drill is through the lens. This avoids leaving a frayed exit point.

7. Groove poly by running the lenses through the cycle twice. First, groove to half the depth, then groove to the full depth.

8. Some manufacturers' hard coatings may interfere with tinting. Check with lens manufacturers to determine tint capability.

9. Keep tint bath temperature from 205 to 210 degrees Fahrenheit for the best results. Do not use alcohol or acetone to clean poly lenses.

TRIVEX TIPS

When Trivex hit the scene in 2001, it was hailed for its impact-resistance, light weight, thinness, and good optics. And since then, most edger manufacturers have added Trivex to their "all material" capabilities. Top Trivex tips include:

1. A vacuum system attached to the edger removes sward and airborne particles and minimizes clogging.

2. Use "acrylic, other material, or polycarbonate" edger settings.

3. Use the slow wheel speed.

4. Use high-speed blade/cutters on polycarbonate settings.

5. If high friction is a problem, adjust head pressure.

6. Keep in touch with manufacturers for the latest techniques.

7. Dry edging is recommended; use water only on the final rotation.

8. Use wheels, pads, and other processing accessories that have been developed for Trivex material.

Advancing technology has created the best in lens material, and edger manufacturers have stayed in step. With a little research, and perhaps an upgrade here and there, there's no reason to shy away from poly or Trivex.