Eye on Equipment
Small PALs, No Problem
By Susan P. Tarrant

Ahough the newer automatic patternless edgers can handle small PAL designs, there are special challenges. Here, equipment experts provide hints on making an easy process even easier.

WHEN BLOCKERS BLOCK

PROBLEM: When edging lenses with small B corridors, the block interferes with our machine's edging function.

SOLUTION: You are using your patternless edger in "active layout mode," so the operator blocks on optical center, and the machine does the decentration for you. If you're dealing with a small B, the height of the fitting cross needs to be high and the block has to go almost to the top of the lens.

Edge the lens in "passive mode." The operator manually blocks on geometric center rather than optical center, and the block is equidistant around the frame.

--Franco Aluigi
product manager, Santinelli International

RAISING THE ADD

PROBLEM: In many instances, if a small frame is chosen (a B measurement of 25 or less), the near vision area may be eliminated during edging.

SOLUTION: Some opticians familiar with PAL designs will request a higher add than the patient's prescription.

Let's say a patient requires an add of 1.5 for his near vision. The dispenser will request the lab to surface a 2.0 add lens in anticipation that the near will be edged off and the patient's true utilized near vision will be part way down the channel.

--Marc Okrant
group product manager, Gerber Coburn

Small PALs can be handled in house, with the right tools and knowledge. Shown, Shamir Insight's Piccolo

AVOIDING TWISTS

PROBLEM: How can I avoid small PALs twisting off axis during cutting?

SOLUTION: Use a patternless edger with variable speed selections for cutting fragile or slippery lenses. The setting automatically adjusts motor speed and lens direction as it makes contact with the grinding wheel to avoid twisting. An edging system with an integrated tracer and blocker, or a tracer that "talks" to the blocker, will allow you to check the segment location using the progressive markings and to verify cut-out before edging.

If the edger can't cut small enough, you'll have to cut the lens to a larger diameter and finish it with a hand edger.

--Shelton Green
lab sales consultant, Briot-WECO USA

SHAPING A SOLUTION

PROBLEM: When I edge small PALs, the near add power gets cut off.

SOLUTION: With some edging systems, an operator can create custom shapes with rimless or drill mount frames by extending the bottom portion of the shape. If the near add power of the PAL is going to be partially cut off, it can be extended to avoid cutting off the near add power. Otherwise, PALs are as easy to do as single vision.

--Matt Vulich
vice president, sales, AIT Industries