Finite Element Analysis of PMMA Stretch Blow Molding

The electric bubbles are a useful product made of PMMA material. They are produced by the stretch blow molding process. Thickness, which reflects the quality of the electric bubble, is a crucial parameter that deserves special attention for the molding process. In this work, finite element simulations of the stretch blow molding process are performed aiming at the determination of the preform geometry to ensure homogeneous thickness of the finished product. The geometrical parameters of the preform are optimized allowing a better homogeneity thickness compared to existing data. The predicted parameters allow the improvement of the thickness distribution. The standard deviation of the thickness is reduced to about 95% compared to the existing bubble. 1. Introduction Stretch blow molding is one of the most important manufacturing processes of polymer via injection process [1–3] or extrusion process [4, 5] to produce hollow plastic parts. The majority of clear bottles are produced using injection stretch blow molding process. Accordingly, several works were devoted to the simulation of the stretch blow molding in order to optimise the process and improve the quality of these containers. Chung [6] proposed a finite element (FE) model for injection stretch blow molding of PET bottles using the software ABAQUS. These simulations focused on the optimisation of the side wall thickness of the bottle by adjusting the variations of histories of plunger movement and gas pressure. Cosson et al. [7] used the so-called constrained natural elements method to simulate and optimize the stretch blowing of a PET preform by assuming an axisymmetrical and viscoplastic preform model under an internal pressure. The thickness of the bottle is linked to the variation of the stretch rod speed and time where the blow pressure is applied. Cosson et al. [8] simulated the stretch blow molding process of PET bottles at the usual process temperature. The simulation results modeled the crystalline microstructure evolution and predicted the elastic behaviour of the final bottle. It also provides Young’s modulus distributions in the bottles. Tan et al. [9] developed a 2D isothermal FE simulation of the injection stretch blow molding process for PET containers. To inflate the PET preform, two approaches were used in the simulation: (i) a direct pressure input and (ii) a constant mass flow rate of air. The results show that the simulation with the fluid flow method gives good prediction of the volume versus time curve and the preform shape evolution. Tan et al. [9] concluded that applying