Optimization Design of Porthole Die to Enhance Metal Flow Stability for Thin-Wall, Asymmetric, Unequal-Wall-Thickness (TW-AS-UWT) Aluminum Profile Extrusion

In order to meet the production requirements of high safety and lightweight, the battery cases of new energy vehicles use a special structure with thin wall, asymmetric configuration and unequal wall thickness (TW-AS-UWT). The aluminum profile produced by the conventional die exhibited poor dimensional precision and severe wrinkling instability. This paper addresses the optimization of the design and simulation analysis for extrusion die, to enhance the dimensional precision and effectively regulate the wrinkling instability of the AA3003 TW-AS-UWT profile. The material distribution ratio of the porthole die was calculated by the cross-sectional area of profile, thereby ensuring a reasonable diversion of the billet. Furthermore, a bearing height of “steps + bumps” was designed to adjust the metal flow resistance and to match the extrusion process. The optimal bearing height of the steps was h_tk (8.5 mm), h_md (6.0 mm), h_th (5.0 mm), and the bumps (h_pt, h_pm) were 0.5 mm. Moreover, the simulation outcomes for the two models demonstrated a considerable reduction in the mean square deviation for flow stress, velocity and temperature in the modified model. This indicates that the optimized design has the potential to enhance the welding quality, diminish the metal dead zone and facilitate uniform material flow of the profile. Additionally, it can maintain dimensional precision of the thick-walled and thin-walled sides within the specified limits of ± 0.035 and ± 0.02 mm, respectively. The length of bending at the outlet was reduced from 5 to 3 meters, which meets the subsequent mass production manufacturing requirements for the battery case.