A Numerical Simulation of Meshes Mending Used in the Three-dimensional Porthole Die Extrusion of Thin Wall Profiles

Aims: The variety of aluminium products used in many industries (e.g., aviation, railroad, and transport) drive the need for an urgent increase in aluminium feedstock. Improved aluminium extrusion forming and mold design guarantee product quality, shorten production time, and enhance mold life. We analyse and discuss the problems resulting from the simulation and analysis of thin-layer aluminium alloy rims by focusing on porthole die extrusion for bicycles. In general, when analysing with CAE, the billet going from portholes to the welding chamber in the hot extrusion forming process indicates that mesh penetration during remesh causes volume loss and stops the simulation. This is especially serious on thin wall products.

Methodology: In this study, applying mesh mending to extrusion of the billet could solve this problem, and the previous issue of mesh contact causing volume disappearance would not appear during simulation. After solving the remesh problem, the optimisation method in the Taguchi Method could be utilised to modify the hot extrusion mold and analyse its existing speed to avoid uneven forming.

Results: Our analysis simultaneously examined stress, strain, velocity gradient, and product formation to understand the relationships between parameters and extrusion load as well as forming defects caused by thin wall extrusion. It is expected to provide a specifically practicable analysis model for aluminium extrusion.

Conclusion: Comparing the simulation size with design size ensures accuracy. The maximum size error was 8.70% at a size of 0.92mm, and the maximum error of the rest of the sizes was about ±5%, which was acceptable in this study.