Injection compression molding is a process having a compression action in the filling or postfilling stages. This process is suitable for molding of parts with precision features. The success of an injection compression molding process relies on proper design of the mold and selection of process conditions. The main scope of this study is to develop an analysis tool for the residual stresses and shrinkage of an injection compression molding process. A simple thermoviscoelastic model was used to calculate the stress and relaxation developed in the postfilling stage. The model divides the thickness into two regions, glassy and rubbery phases. Residual stress calculation is applied in the glassy region, while the rubbery region is kept at the melt pressure without any strain because of the fast relaxation in this region. The resulted in-mold stress fields are used to calculate the part shrinkage after demolding. The effects of the compression force on the residual stresses and shrinkage of a molding part were also investigated. Higher compression force tends to reduce the part shrinkage but induces a higher level of residual stresses.
© 2003, Carl Hanser Verlag, Munich