TW215426B - Process for molding extra thin plastic lenses - Google Patents

Abstract

A process for molding extra thin plastic lenses makes use of a movable optical core cavity associated with an injection molding machine that uses closing clamp pressures to perform a compression function to execute the following steps. (1) The injection molding machine partially closes the mold plates at its first stroke, forming an enlarged cavity that has a larger lens thickness than the designed value. (2) The cavity consists of two separated cavity cores that are independent of the mold base. At least one of the cavity cores is able to move towards or away from to the other one. The movable cavity core reaches its position in the second closing stroke of the injection molding machine. (3) There is an injection gate that locates near one end of the lens cavity core and near the other end at least one overflow system that consists of overflow gates and special designed overflow wells. (4) Plastic materials enter the cavities and the overflow systems. The injection machine performs a compression stroke before the injection operation terminates to reduce the cavity volume. (5) The second closing stroke and a location device of the mold determine the final cavity volume.