A Novel Analytical Equation for Front Scrap Allocation in Direct Aluminum Extrusion

At the end of each process stroke, the back end of the old billet material that completely fills the die starts to interact with the front side of the new billet loaded into the press that is usually contaminated by oxides, dust or lubricant, thus producing a transition zone that extends to a variable length. In the case of structural applications, it then becomes clear that the length of the profile marked by the charge welds must be scrapped and an accurate prediction of this portion becomes mandatory. For this purpose, analytical equations are available in literature, but they show poor predictability. On the contrary, several contributions have been proving that finite element analysis (FEA) is the most reliable approach to scrap prediction; however, FEA is seldom accessible to extrusion companies and therefore, the industry is still looking for a valid alternative. This paper presents a new user-friendly equation comparing quantitatively its predictions with numerical ones. Finally, the authors describe how to use the novel equation at its best thanks to selected case studies