This paper deals with various cases for PET (polyethylene terephthalate) in two-stage stretch blow molding process with a transparent mold and a digital camcorder. The simulations were carried out by POLYFLOW software with K-BKZ viscoelastic model. The predicted wall thickness distributions of the formed bottle were found to be in good agreement with those of experimental measurements. Under same reheating treatment, the two factors, both of the stretch rate and the time sequence of the rod movement and the gas blow, show more great influence on the thickness distributions of final bottle than blow pressure. Besides the three cases of the preform free blow, and the air pressure applied after/before the stretching rod touched the bottom of the mold cavity, the interaction of the two factors may cause another phenomenon, which is the stretching rod touches off the preform bottom after the rod pulls it for a moment. The phenomenon easily makes for an eccentricity of the bottle bottom.

Volume Subject Area:
Fluids Engineering
Keywords:
injection stretch blow molding, PET, simulation, thickness distribution, process parameter
Topics:
Molding, Simulation
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