EXPERIMENTAL AND THEORETICAL INVESTIGATION OF THE INFLATION OF VARIABLE THICKNESS PARISONS

In today's blow molding of complex parts, an optimal resin distributio n is critical to a successful operation. These goals are mostly attain ed through a technique known as parison programming. The process invol ves varying the die gap during extrusion and therefore results in a pa rison having a variable thickness along its length. The subsequent inf lation of a variable thickness parison is a complex phenomenon involvi ng the interaction of many process variables. The final thickness dist ribution and inflation patterns were obtained for various programmed p arisons. Constant, one step, two step, and sinusoidal thickness pariso ns were studied. The inflation patterns were monitored by employing a transparent mold in conjunction with a video camera. The experimental data indicated the presence of an oscillatory inflation pattern for so me of the variable thickness parisons. The experimental final part thi ckness distribution for these cases was highly nonlinear. Theoretical predictions of the final thickness distribution were also obtained for some of the cases. The simulation is based on the inflation of a Moon ey-Rivlin hyperelastic material. A wide range of deformation is accoun ted for by introducing an evolutionary Mooney constant, dependent on t he level of deformation.