Design of the Complex Aluminum Bridge Extrusion Die Through Finite Element Analysis

Abstract

In this study, the aluminium bridge die extrusion process for AA6061 alloy was investigated using a coupled thermomechanical finite element analysis (FEA) combined with industrial extrusion experiments. The process parameters, including die temperature, ram speed, billet diameter, and billet length, were defined according to industrial production conditions. Unlike conventional approaches that evaluate die parameters separately, this study presents an integrated optimization of a complex bridge die by simultaneously modifying baffle plates, pocket geometry, and bearing lengths.

The numerical model was used to analyze the temperature and velocity distributions at the die exit and to evaluate stress levels within the bridge die structure. The initial die design exhibited severe flow imbalance, characterized by a high velocity relative difference (VRD ≈ 25.3%) and excessive exit temperatures, which led to profile bending, dimensional deviations, and insufficient welding pressure.

Through systematic design modifications, the optimized die configuration significantly improved the flow balance, reducing the VRD to approximately 4.6% while maintaining exit temperatures within the desired range. The improved metal flow also increased the welding pressure and enhanced the dimensional stability of the extruded profile. Mechanical tests confirmed the effectiveness of the optimized design, showing increases in tensile strength and yield strength, as well as a more uniform hardness distribution across profile regions with varying thickness.

The results demonstrate that a coordinated optimization of baffle plates, pocket geometry, and bearing lengths is essential for achieving balanced metal flow and high weld quality in bridge die extrusion. The combined numerical–experimental approach provides a reliable methodology for improving the performance and structural reliability of complex aluminium extrusion dies used in industrial production.