International audienceThe injection stretch/blow molding process of PET bottles is a complex process, in which the performance of the bottles depends on various processing parameters. Experimental work has been conducted on a properly instrumented stretch/blow molding machine in order to characterize these processing parameters. The objective being a better understanding of the pressure evolution, preform free inflation has been processed and compared with a simple thermodynamic model. In addition, a numerical model for the thermomechanical simulation of the stretch/blow molding process has been developed. At each time step, mechanical and temperature balance equations are solved separately on the current deformed configuration. Then, the geometry is updated. The dynamic equilibrium and the Oldroyd B constitutive equations are solved separately using an iterative procedure based on a fixed-point method. The heat transfer equation is discretized using the Galerkin method and approximated by a Crank-Nicholson's scheme over the time increment. Successful free blowing simulations as well as stretch/blow molding simulations have been performed and compared with experiments

Stretch blow molding or thermoforming processes includes an infrared heating stage of the thermoplastic preform by infrared heaters. The knowledge of the temperature distribution on the surface and through the thickness of the preform is important to make good prediction of thickness and properties of the manufactured parts. Currently in industry, the fitting of the process parameters is given by experience and is expensive. Our objective is to provide tools that are able to simulate the heat transfers between infrared heaters and preforms in order to reduce the fitting cost and to control the qualities of the end products. The optical method called "ray tracing" is used to simulate the radiative transfer. First, we compare the ray tracing method with the view factor method on a simple example: the heating of a square sheet by one infrared lamp. Then, we perform 3D heating stage simulations and compare with experiments. The ray tracing method allows to compute a source term in the transient heat balance equation. Then commercial finite element method softwares can be used to solve the heat balance equation.

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible.