HYBRID APPROACH FOR MODELING OF PARISON EXTRUSION IN BLOWMOLDING

Abstract

Appropriate parison dimensions (diameter and thickness) are crucial for the successful blowing of a part. These dimensions are fonctions of material properties as well as the history experienced by the material in the extrusion die. Previous attempts to model parison formation at industrial operating conditions (high flow rates) have been largely unsuccessful. This work proposes a novel hybrid approach for modeling of parison formation for straight die. The approach determines the stress inside the die as well as the parison dimensions. Inside the die, the tracking procedure for material elements is applied to steady flow, using the K-BKZ model, as proposed by Wagner, for predicting the stress ratio at the die exit. The velocity profiles are calculated numerically using the finite element method. The parison dimensions are determined using the approach proposed by Tanner, which relates the swell to the stress ratio at the exit of the die.