EXPERIMENTAL-STUDY AND NUMERICAL-SIMULATION OF THE INJECTION STRETCH BLOW MOLDING PROCESS/

The injection stretch/blow molding process of PET bottles is a complex process, in which the performance of the bottles depends on various p rocessing parameters. Experimental work has been conducted on a proper ly instrumented stretch/blow molding machine in order to characterize these processing parameters. The objective being a better understandin g of the pressure evolution, preform free inflation has been processed and compared with a simple thermodynamic model. In addition, a numeri cal model for the thermomechanical simulation of the stretch/blow mold ing process has been developed. At each time step, mechanical and temp erature balance equations are solved separately on the current deforme d configuration. Then, the geometry is updated. The dynamic equilibriu m and the Oldroyd B constitutive equations are solved separately using an iterative procedure based on a fixed-point method. The heat transf er 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.