Do you ever watch those TV shows about “How It’s Made?” It’s often fascinating to see the ingenious manufacturing processes that go into creating what seems like a simple object. It’s no different with ophthalmic lenses! Here are three basic ways that semi-finished lenses are made:
Typically used for hard resin & high-index lenses. Liquid monomer is injected into glass mold assemblies and put through a heat cycle, usually in either air ovens or water baths. This tends to require intensive hand labor and automation is typically low.
Typically used for polycarbonate. Large, specialized injection molding machines run long cycles. Molds are either expensive steel dies or glass molds. Pellets are molded into lenses under great pressure. This tends to require expensive equipment and can be highly automated.
Specialized Rim Injection Molding:
Typically used for Trilogy/Trivex lenses. Components are mixed by a very complex machine under high speed and quickly begin reacting and hardening inside a mold assembly very similar to that used in casting. This tends to require expensive equipment AND intensive hand labor.
In all types of lens manufacture, special attention must be paid to lens cosmetics, hardness, curve control, color, and many other specifications. One thing is for sure, any way you make them, lens manufacture is tough, and perhaps one of the most rigorous forms of plastics manufacturing. I feel lucky to be part of this fascinating industry!