Abstract: In order to produce precision optic elements using injection molded plastic, a metal mold is fabricated from two positive masters comprising exact metallic reproductions of the desired plastic part and on which a metal shell has been electroformed or otherwise plated. Two positive masters are required for each mold, one being formed to define the upper part of the mold and the other the lower part of the mold. Each positive master is scribed with an axial line and with a cutting line slightly offset from the axial line, the cutting line for the upper part of the mold being below the axial line and the cutting line for the lower part of the mold being above the axial cutting line. The positive masters are then cut along their cutting lines, the metal shells removed, and the portion of the remaining metal shells between their axial lines and their cutting lines is then trimmed. The upper and lower parts of the mold are then combined to define the complete injection mold.

Abstract: In order to produce precision optic elements using injection molded plastic, a metal mold is fabricated from two positive masters comprising exact metallic reproductions of the desired plastic part and on which a metal shell has been electroformed or otherwise plated. Two positive masters are required for each mold, one being formed to define the upper part of the mold and the other the lower part of the mold. Each positive master is scribed with an axial line and with a cutting line slightly offset from the axial line, the cutting line for the upper part of the mold being below the axial line and the cutting line for the lower part of the mold being above the axial cutting line. The positive masters are then cut along their cutting lines, the metal shells removed, and the portion of the remaining metal shells between their axial lines and their cutting lines is then trimmed. The upper and lower parts of the mold are then combined to define the complete injection mold.