EYE ON EQUIPMENT
Edging Those �Extra-tough� Jobs
By Susan P. Tarrant

Service is important to every optical location�whether it�s how patients are treated in the waiting room; how well their visual problems are detected in the exam room; or how well their visual needs are taken care of in the dispensary. And certainly you want to give your patients the best lens possible, at the best price possible, in the quickest time possible. That is, after all, why you invested in your in-house processing equipment in the first place. So opting to send a lens job out to be processed is to be avoided if it all possible, right?

But sometimes there are just those jobs that need a little extra finesse, or a little extra know-how. That�s where our equipment experts come in, and we�ve gathered some here to address those bothersome jobs and provide hints at how you can keep them in-house.

Caution: Curves Ahead

PROBLEM: I had traditionally been sending jobs with higher base curves out to a lab to be processed, but I have upgraded to a three-axis generator in order to keep those jobs in-house. How can I successfully surface the backside of the lenses when the base and cross curves are a minus 11 or more?

SOLUTION: A three-axis generator does indeed extend your capabilities to process jobs in a wide range of powers and gives you the ability to cut your own lap tools in approximately five minutes. The following steps, however, should be taken to ensure success:

1. Begin by making sure you always choose the proper base curve. If the power is above a minus 11, you might want to consider using a minus front base curve.

2. When the base curve is a minus 11 or higher, you willl need to cut a �high-hat� lap tool that will match the curves specifically. This type of tool will have the smaller diameter and a steeper curve needed to process a high-minus job. To produce a �high hat� lap tool, begin wth raw lap blanks from any manufacturer.

3. Using the raw lap blank, cut the lap and verify the curves with a sag gauge. The tolerance should be plus or minus .02 of sag value.

4. Perform the calculation and data entry, and then cut your lenses in the usual manner.

�Stuart Watson, National Optronics

When Poly Doesn�t Wrap

PROBLEM: It is difficult to edge polycarbonate lenses for sport goggles that wrap around the face. Is there a way to keep these jobs in-house?

SOLUTION: Many styles of athletic goggles have a severe wrap to them. When you�re using a traditional pattern edger, you need to use lenses that are ground on an eight base curve or higher, and you most likely still will need to place the bevel on the lens by hand. The curve of the eyewire also will have to be modified to accommodate the lenses.

However, sport goggles can be processed more easily on a 3-D patternless edger because these machines can curve the bevel so that it�s a perfect fit without straightening the goggle. With a good 3-D system, you don�t have to special-order lenses with a higher base curve.

�Bill Galindo, ODI/Topcon

Scratchy Problems

PROBLEM: I�d like to promote more polycarbonate in my optical shop, but I�m having problems edging it. Many jobs get scratched during processing.

SOLUTION: To prevent the softer poly material from scratching during processing, use slip-stop guards to protect the lenses. These clear, round disks should be placed between the lens and the leap pad and on the backside of the lens where the chuck makes contact.

�Matt Vulich, A.I.T. Industries

High Index, High Re-do Rate

PROBLEM: When processing high-index lenses, the automatic edger cuts the lenses a little too thick, forcing a touch-up or re-do.

SOLUTION: High index is a denser material than CR 39, regular plastic. Therefore, if you�re dealing with an automatic machine and set it for �plastic,� the lens will automatically be cut a little thicker. If you are working with an edger that has a separate setting for high index, you�re all set.

Many machines don�t have a separate setting for high-index, however. In that case, simply create a conversion chart. Keep track of the margin of error you are experiencing for each lens index. That error should be consistent. For example, every time you cut a 1.60 lens, the finished lens should be a certain number off every time.

Keep track of that error margin, and you should be able to avoid retouching the lens by simply entering the �converted� number into your machine before you even begin.

�Rick Noonkester, regional manager,Santinelli International

Bevel Curves and eyewire curves don�t see eye to eye

PROBLEM: With small frames, I sometimes have trouble with the curvature of the beveled lenses being different than the curvature of the eyewire.

SOLUTION: Depending upon the equipment you have, changing the bevel setting may be all that is required. The newest, three-axis, 3-D finishing systems calculate optimum bevel position by capturing and factoring the frame curvature, the lens curvature, and its thickness. These calculations will at least assure that the bevel remains on the lens, minimizing breakage. In addition, these controlled bevels will cut down on the need to bend the frame to accommodate the lens.

�Michael Urban, Gerber Coburn

When AR Gets Scratched

PROBLEM: How can I avoid scratches when finishing AR-coated lenses?

SOLUTION: The film coating on the surface of AR-coated lenses makes them more vulnerable to scratching. First, it�s important to keep your edger�s finishing chamber clean and free of any debris that might scratch the lens. The best edging systems feature a three-way water delivery system that automatically flushes the edging chamber while edging and when idle to constantly remove any lens fragments or debris.

Second, minimize operator handling. The less a lens is handled, the less chance there is for operator-caused scratches to occur. Handling mishaps can be avoided by using an all-in-one edger.

Lastly, it�s important to maintain a clean lab environment because any foreign material on your hands, in the job tray or work area could scratch the lenses.

�Greg Dean, technical training manager, Briot