Overall numerical simulation of extrusion blow molding process

This paper focuses on the overall numerical simulation of the parison forma tion and inflation process of extrusion blow molding. The competing effects due to swell and drawdown in the parison formation process were analyzed b y a Lagrangian Eulerian (LE) finite element method (FEM) using an automatic remeshing technique. The parison extruded through an annular die was model ed as an axisymmetric unsteady nonisothermal flow with free surfaces and it s viscoelastic properties were described by a K-BKZ integral constitutive e quation. An unsteady die-swell simulation was performed to predict the time course of the extrudate parison shape under the influence of gravity and t he parison controller. In addition, an unsteady large deformation analysis of the parison inflation process was also carried out using a three-dimensi onal membrane FEM for viscoelastic material. The inflation sequence for the parison molded into a complex-shaped mold cavity was analyzed. The numeric al results were verified using experimental data from each of the sub-proce sses. The greatest advantage of the overall simulation is that the variatio n in the parison dimension caused by the swell and drawdown effect can be i ncorporated into the inflation analysis, and consequently, the accuracy of the numerical prediction can be enhanced. The overall simulation technique provides a rational means to assist the mold design and the determination o f the optimal process conditions.