ABSTRACT
Since the Hyatt brothers received a patent for a ram injection-molding machine in 1872, injection molding of polymers has been an important processing operation [1]. A variety of complex and sophisticated parts are injection molded in the modern plastics industry from a wide range of thermoplastic materials. At the same time the rubber industry has traditionally used compression and batch blow molding to fabricate commercial products [2]. These processes require hand operation and are highly time consuming and difficult to automate. The injection molding of rubber by a ram injection machine emerged 40 or more years ago, with the first user apparently being Chrysler [3]. Screw injection molding of rubber was first reported in the 1950s. Ram and screw injection-molding machines have been actively marketed since the 1960s. The most important feature of injection molding is that it allows introduction of a high degree of automation in the rubber industry. In addition, rubber compound preparation and cure time can be reduced, and trimming of molded product can be practically eliminated.
