How sunglasses are made
Plastic sunglasses are constructed from basically three parts. Lenses, frame and temples (arms).
The lenses are manufactured from either glass or plastics such as poly-carbonate. They are made in a mold and then shaped by a special tool tool called a curve generator. Next the lenses edges are smoothed.
Silicon or metal oxides are used to reduce UV radiation transmission. The oxides can also create the desired colour tint to the lenses or organic dyes can be used to tint plastic lenses,
Aluminium or chemical coatings give the lenses the mirrored look.
Frames and Temples
The frames and temples are cut from a sheet of heated plastic then smoothed and polished. The frames and temples are connected with a metal hinge.
The lenses are then snapped into the grooves on the inside of the frames
That's how plastic sunglasses are made