troubleshooting tips
Processing Poly In-House
Karlen McLean, ABOC, NCLC
Processing polycarbonate material in-house continues to be a challenge for many practices, especially as lens treatments evolve. Here's the latest batch of poly edging Q&As.
FRACTURED
Q I'm experiencing a high increase in polycarbonate lens fractures, especially in grooved rimless with premium AR treatment. How do I stop these redos?
A While polycarbonate lenses have many positive attributes, poly rimless jobs have a tendency to fracture more than most materials as a result of stress from being worn. One way to stop the redos is to use lenses with a higher tensile strength, such as Trivex, 1.60, and 1.67, which are great alternatives to poly in rimless mountings and will perform very well with AR treatments.
It's also important to communicate with patients about ways to properly handle their eyewear in order to reduce the risk of stressing the material to the point of fracture. One patient suggestion, regardless of material, is to use the bridge when removing eyewear. This can help reduce stress on rimless drill holes.
—Sam Odom, manager, technical marketing and education, VSP Labs
FRAYED
Q My poly edges are getting frayed and raggedy-looking. What causes this and how do I fix it?
A This happens when lenses are run in the wrong edging cycle. Poly lenses must go through the roughing cycle on a dry wheel. Water cooling will cause swarf to stick to the lens edge and is nearly impossible to remove. The finishing cycle should be done with a light mist—too much water cooling will again cause swarf to stick. Also, when a lab runs a very high concentration of poly, the excess swarf begins to load up on the edging wheels, causing them to not cut properly because the diamonds are no longer exposed.
Edges will be rough and it will be almost impossible to achieve a nice polished edge. To clean the swarf off, try to mix CR39 Rx's in on every fourth or fifth job.
—Mike Sutherlin, vice president, Sutherlin Optical, Kansas City, Kan.
| BEST Practices |
|---|
| Q We're revamping our in-house finishing procedures with a focus on polycarbonate. What's the current best practices method for edging poly? A Edger set-up is key. You need to have a good, aggressive roughing wheel. Dry cut on the roughing wheel, then in the bevel cycle. While the lens is in its final beveling cycle, add water to give it a shiny, smooth finish. That being said, every edger is different. Keep in mind that most edgers don't do everything for you. For example, they may not use diamond wheels and they have different types of blades. The art as well as the science of edging is still required to output a good job. —John Haskins, president, Slabs Plus, Ruskin, Fla. |
If you have a question you'd like to have answered in Ask the Labs, send it to Karlen McLean. Email: Karlen.McLean@WoltersKluwer.com. An archive of past Ask the Labs columns can be found on the Eyecare Business website at www.eyecarebusiness.com.
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