Bearing lengths for extrusion dies: rationale, current practice and requirements for automation

Abstract

This paper concerns the assignment of bearing lengths used to control flow in flat-faced aluminium extrusion dies. The published literature shows the complex nature of flow during extrusion. Many inter-related factors must be considered if the flow in an individual die is to be accurately modelled. Consequently, bearing lengths in production dies are determined by skilled die designers, whose knowledge of flow is based on experience. An investigation of their techniques shows that common principles exist, despite individual differences in approach. Standardisation of die design often takes the form of rules based on die designers' techniques. Extant semi-automatic design systems are based on these rules or simple flow models, but such systems rely on skilled human interaction. Based on this review of current practice, the requirements for full automation of bearing length assignment are presented together with a set of test shapes for the validation of such methods.