Finite element modeling and experimental study of injection blow molding

Injection blow molding is an important commercial process for the production of hollow plastic articles. A finite element computer program of the inflation stage has been developed for engineering design purposes. The program is based on the assumption that the molten polymer behaves as a rubber-like elastic solid during the rapid inflation stage. The program is capable of predicting the final wall thickness distribution of many symmetrical blow molded parts.; Injection blow molding experiments were conducted under industrial conditions. The experiments confirm the assumption of almost complete elastic behavior during inflation. Qualitatively there is good agreement between the computer model and the experimental results. Nonuniformities in the temperature distribution in the material have a significant impact on inflation behavior which can be related directly to the temperature dependence of Young's modulus. Computer predictions of the experimental wall thicknesses are not completely satisfactory although this may be due to an imprecise knowledge of the initial temperature distribution.