Optimisation of Preform Temperature Distribution For the Stretch-Blow Moulding of PET Bottles

Abstract

This study presents an optimization strategy developed for the stretch-blow moulding process. The method is based on a coupling between the Nelder-Mead optimization algorithm, and Finite Element (FE) simulations of the forming process developed using ABAQUS®. FE simulations were validated using in situ tests and measurements performed on 18.5 g – 50 cl PET bottles. To achieve that, the boundary conditions were carefully measured for both the infrared heating and the blowing stages. The temperature distribution of the perform was predicted using a 3D finite-volume software, and then applied as an initial condition into FE simulations. Additionally, a thermodynamic model was used to predict the air pressure applied inside the preform, taking into account the relationship between the internal air pressure and the enclosed volume of the preform, i.e. the fluid-structure interaction. It was shown that the model adequately predicts both the blowing kinematics and the thickness distributions of the bottle. In a second step, this model was combined to an optimization loop to automatically compute the best perform temperature distribution, providing a uniform thickness for the bottle. Only the last part will be fully detailed in this paper.