Importance

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Abstract

Method and apparatus for injection compression molding of thermoplastic parts. A preferred apparatus (100) includes a platen assembly 106, a toggle clamp assembly 102, a screw injection assembly 101, a hydraulic system suitable for providing power to the toggle clamp assembly 102 and the screw injection assembly 101, and a control system 88 for operatively controlling the various hydraulic devices associated with the molding apparatus. The platen assembly 106 provides for a plurality of variable-volume mold cavities 7. In one embodiment, enlarged mold cavities 7 receive plasticized resin from the screw injection assembly 101, and compression of the injected resin is provided by the toggle clamp assembly 102. In another embodiment, the platen assembly 106 includes a floating die assembly wherein pressure created by injected resin causes die inserts 5 and support pillars 15 to slide relative to a molding plate 74. Compression in this embodiment is also preferably provided by the main toggle clamp assembly 102. Preferably, the toggle clamp assembly 102 provides multiple-stage compression of the resin to first redistribute the resin and vent the cavities and, second, compress the resin to compensate for cooling-induced shrinkage thereof. In the multiple cavity embodiment, because all cavities 7 are equally compressed simultaneously, control of the molding process and balancing of the mold are readily accomplished. The method and apparatus are particularly well suited for molding optical lenses and disks. Printed circuit substrates can also be molded thereby.

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First Claim