Modeling of deformation processes in vacuum thermoforming of a pre-stretched sheet

Modeling of deformation processes in vacuum thermoforming for a preliminary stretched thermoplastic sheet (plug-assist vacuum thermoforming) is investigated in this paper. The model can be used for production of polymeric articles with minor wall-thickness variation. A nonlinear rheological model is implemented for developing the process model. It describes deformation process of a prestretched sheet at any phase of vacuum thermoforming process. This process is described by a set of deformation processes, each specified by appropriate boundary conditions. For model validation, a comparative analysis of the theoretical and experimental data is presented. The wall-thickness distributions obtained from modeling results corresponded well with experiments. A method for prediction and enhancement of the quality of the final products on the basis of wall-thickness distribution criterion has been established.