Influence of dynamic temperature control on the injection molding process of plastic components

Abstract

Conventional injection molding (CIM) technology has been largely used to produce plastic parts, mainly on automotive industry, due to high production ratios, constricted dimensional tolerances production, and low labor costs. Nowadays, industry has been demanding for thinner and lighter molded parts production, with better mechanical properties. Low mold temperatures (≈60ºC) are used to decrease the cycle molding time and process final costs. However, the fast cooling of parts can easily result in surface defects, such as weld lines, sink marks, or warpage. To avoid such defects and eliminate the need for secondary operations (additional operating costs), a dynamic mold heating and cooling control technology known as Rapid Heating and Cooling Molding (RHCM) can be employed. Based on RHCM, this study compared the efficiency of using heating rods, water flow, and external infrared heating systems to investigate the effect of dynamic temperature control on the injection molding process. An experimental injection mold was manufactured and used for the studies under controlled conditions to produce standard tensile and flexure specimens. The effect of process parameters, geometry of the runner system, location of the injection point, and other relevant settings was considered. From this study, new insights were obtained regarding the industrial application of RHCM as well as the degree of efficiency of different design solutions for the RHCM process.