Analysis of Spiral Mandrel Dies with Novel Channel Geometries to Draw Conclusions on the Purging Time of the Melt Using CFD

Abstract: Spiral mandrel dies are deeply integrated into the extrusion process and are the predominant die type for manufacturing products with a ring-shaped cross-section, e.g. blown film. The geometry of the axial spiral mandrel die is characterized by a spiral mandrel with one or more feed holes that merge into the spiral channels. The spiral channels themselves are embedded in the mandrel and have a characteristic u-shape in cross-section, which is dictated by the milling head used during manufacturing. In the past, numerous geometric parameters of the conventional axial spiral mandrel distributor have been examined in the course of optimiza-tions, but the general design is still largely based on the concept of the 1960s. Therefore, this paper presents four concepts for new channel geometries that deviate from the conventional spiral channel cross-sectional shape. All variants were analyzed using a CFD-based algorithm for the automated geometry optimization by varying the general parameters describing the spiral channel. Other defining parameters were kept constant. The results provide insights into the influence of geometry parameters for spiral mandrel dies on purging time.