Injection molding machines invention

William Willert filed a patent on the in-line, now more commonly known as the reciprocating screw injection molding machine in 1952. In 1953 Reed Prentice Corp. was the first to use Willert s invention, building a 600-ton machine. The patent was issued in 1956. By the end of the decade almost all the injection molding machines being built were of the reciprocating screw type. 

An early move toward automation and mass production was the invention of preform machines that sprayed chopped-glass strands onto a three-dimensional air screen that approximated the shape to he molded. The preformed glass mat was placed in a matched metal die in a compression molding press and liquid resin was added to form the product. Today, resin transfer molding (RTM) and resin injection molding (RIM) preform die-molding processes are used to mass-produce small and mid-size parts with two finished sides, notably automobile bodies, truck cabs, and even small boat shells. 

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