Dimensional study of thermoplastic parts made using sequential injection molding

As a result of new aesthetical and economical requirements in injection molding, several processes have been developed during last years. In spite of conventional process, sequential injection molding is a versatile technique based on independent control for each gate opening. This procedure allows part filling without weld lines or, at least, these defects can be relocated in suitable positions. A short discussion about sequential principles is made introducing computer simulations. Pressure required for part filling and molding shrinkage were evaluated using experimental procedures with a prototype mold and using conventional and sequential methods. Several setting up parameters were also used to analyze the effect on injection process. Final results show that shrinkage in sequential injection is similar to conventional process but some new effects could be induced by the process asymmetry and should be investigated further. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers