Effect of pocket design on metal flow through single-bearing extrusion dies to produce a thin-walled aluminium profile

Pocket dies, commonly used in the manufacturing of solid aluminium profiles, allow the extrusion operation to run in a semi-continuous manner. The pocket in front of the die bearing can be utilised to regulate metal flow and achieve homogeneity in flow velocity on the cross-section of the extrudate. Across the extrusion and tooling industries, the design of pocket dies relies on the intuition and experience of the designer. The design of the pocket becomes more challenging when the die is used for the manufacturing of a wide thin-walled profile. The present research concerns an investigation of the effects of pocket geometric parameters on metal flow by means of finite element (FE) simulation in combination with experimental verification. A series of single-bearing dies with pockets of different sizes, volumes and shapes were designed. A flat die without pocket was used as reference. Three-dimensional FE simulation of extrusion to produce a thin-walled aluminium profile with a large aspect ratio and thus an inherent tendency of inhomogeneity in flow velocity across its width was performed. The velocity distributions of the extrudate through these dies were revealed and the geometric parameters of the pocket affecting the metal flow collated. In addition, the effects of pocket geometric parameters on extrudate temperature and extrusion pressure were determined both numerically and experimentally. The results obtained provide the fundamentals and also practical guidelines for the design and correction of pocket dies to produce aluminium profiles.