Simulation And Software Development Of Forming Process On PET Drinking Bottles

Injection stretch-blow molding method is the third main method for plastic forming, and it is widely used to make PET drinking bottles. Its forming process is so complicated that both the manufacturing cost and bottle performance are affected. Thus, the experts at home and abroad have been studying the stretch-blow and cooling process through many methods, so that the optimization can be finished according to the simulation results.Firstly, PET material and principle of stretch-blow molding were introduced. Control equations, viscosity models of stretch-blow molding phase and cooling curing phase were given. Detail process of FEM building of mold, stretching rod, perform and methods to solve stretch-blow molding model were introduced.POLYFLOW software was used to simulate stretch-blow molding phase and cooling curing phase of PET bottle forming process. Its analysis were about influences on bottle thickness distribution of process conditions, preform structure type and mesh grid, etc. Of that, the analysis on cooling process started with the stretch. The situation of temperature change can be reflected truly. The influence of the initial temperature distribution on bottle thickness was analysized. Comparison was made about deformation and influences on bottle thickness of positive cone and negative cone preform. From the view of theory and simulation, stress situation of molding phase was analsized and reasons of preform deformation were given. Combined with simulation results and problems, factors that influenced performance of PET bottle were summarized.Based on results of FEM and theory, optimization of forming process was implemented. Genetic algorithm and parison programming were used to optimize structure of preform and process conditions. Optimization results could be used to guide actual process.At last, VC++6.0 was used to develop software for PET bottle simulation and analysis based on above simulation and optimization results. Database was established. This system can be used in practice perfectly.