Injection molded parts are drivendown in size and weight especially for portable electronic applications.While gains are achieved via cost reduction andincreased portability,thinner parts encounter more difficulty in molding due to the frozenlayer problem.To increase moldability in thin wall molding,a rapid thermal response (RTR) mold was investigated.The RTR mold is capable of rapidly raising the surface temperature to the polymer melt temperature prior to the injection stage and then rapidly cooling to the injectionstage and then rapidly cooling to the ejection temperature.The resulting filling process is done inside a hot mold cavity and formation of frozen layer is prohibited.Concepts of scalable filling and low-speed filling are discussed in the article to address the benefit of this molding method.Simulation results showed that significant reduction in injection pressure andspeed can be achievedin RTR molding.In contrast to the filling behavior in conventional molding,the injection pressure in RTR molding decreases as the injection speed decreases,and therefore,extemely thin parts can be molded at lower injection speeds.Filling lengths of both RTR and conventionally molded polycarbonate samples,with two levels of thickness,under two levels of injection speed were experimentally studied.The experimental results demonstrated the advantage of the new molding method.
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