Warpage of injection-molded thermoplastics parts: Numerical simulation and experimental validation

A mathematical model and the integrated simulation program for predicting part warpage, which arises during injection molding of thermoplastic polymers, were developed. To build the model, the finite element method (FEM) was used and the theory of shells, represented as an assembly of flat elements formed by combining the constant strain triangular element and the discrete Kirchhoff triangular element, was applied. This shell theory is well suited for thin injection molded products of complex shape. Furthermore, in this work, experimental research on flat plates was performed to study the effect of the plastic material, the mold structure, and certain key processing parameters on warpage. The investigated processing parameters include injection pressure, packing pressure, injection time, packing time, cooling time, and melting temperature. Different examples were presented to examine the developed simulation software, and results predicted from the simulation program were verified in the above experiments and showed reasonable accuracy compared with experiment data.