Making AO Ophthalmic Lenses - PART 2
Taken from The American Optical News, Volume 5,
Dated Feb. 11, 1944 - Jan. 26, 1945
The second step in making AO lenses takes place in the Grinding and Polishing Dept. (D3R) which is located in the building directly across the river from the Molding Room. When the glass has been molded and inspected as described in the last issue of the News, it is sent to D3R in trays in lay-out form.
The Grinding and Polishing Dept. is housed in a vast room which is constantly humming with activity and the steady sound of hundreds of bowl feed machines which do the grinding and polishing of spherical, toric and bifocal lenses. Truckloads of lenses go up and down the aisles continuously; the operators at the machines are concentrated upon their tasks, for each step in the grinding and polishing of a lens requires skill and attention. They are artisans in the true sense, for their work on all types of lens grinding and polishing requires an artistry and a perfection of detail that only one who has devoted himself to his work can achieve. The precision required, for example, to obtain the right curve and the proper depth to a lens can be accomplished only by an expert, and the workers are experts in their jobs.
For the purpose of clarity and simplification, the operation to be described is the grinding and polishing of a meniscus or spherical lens; toric lenses, as well as kryptok and all fused bifocal lenses are made fundamentally the same way, but with additional operations.
To indicate these differences and to appreciate the difficulties of producing these latter types, it might be said that there are literally thousands of combinations on toric lenses. Each mold must have its own proper curve and thickness so the lenses will be properly ground, and new molds are made up each day for the following day’s work.
It can be seen, then, that a description of the operations for making these lenses, though they are made in greater quantity than the meniscus lens, would require more lengthy and more involved descriptions. Therefore, for the time being, these processes will not be described, although the skill and knowledge of the men and women who make these types of lenses should not be forgotten.
Preparation for Grinding Spherical Lenses
Upon their arrival from the Molding Room, the circular pieces of glass are placed on concave molds and blocked by filling the block with staybelite pitch. This pitch holds the glass in place so that it can be ground. But first the correct curve is put on the glass by a diamond lap. Then it is ready for grinding.
The Grinding and Polishing
The grinding takes place in the long rows of bowl fee machines. Each operator has a certain number of machines under his control. A fine grade of emery is used which has been carefully washed and prepared downstairs in Department D9R where the emery grading is done. That process, too, is an interesting story that will be told in time. Sufficient to say that an emery grader needs skill - and muscle.
After grind, the lenses are polished in similar machines for a longer period. As the process is longer, each operator has control of more bowls, but skill and accuracy are necessary to the same degree as in other operations. The polishing is done with an iron oxide, or rouge, and a felt which is specially treated with compounds to do the job required of it.
Continued Next Issue
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