We created this animation on the manufacturing process for Trivex lenses a few years ago and I wanted to share it with you.
But, to provide a little more background before you watch the animation, there are primarily two type of processes used to manufacture lenses – casting and injection molding. The majority of optical lens material systems are manufactured by casting – CR-39®, mid- and high index, Trivex® and Tribrid™ materials. Polycarbonate and nylon lenses are manufactured by injection molding.
In an injection molding manufacturing process, the material is forced or injected into the molds. It is a very short process and can take just a couple of minutes to make a lens. Due to the speed of the process and the force used to inject the material into the molds, internal stress can result in the lens, resulting in birefringence and susceptibility to stress cracking.
In case you are interested, I found this video on YouTube that explains the injection molding process.
In contrast to injection molding, the traditional lens casting process is much longer and involves combining components of a lens material system together, filling a glass mold with the material and thermally curing the lens molds in an oven. The curing cycle can take from 7-25 hours to produce a lens, depending on the lens material. The lenses are then removed from the mold (or “demolded”).
Enjoy the video