Abstract: The problem of cavity eccentricity of micro complex hollow extruded profiles such as micro heat pipes in aluminum alloy is investigated, and the corresponding principle of structural design in porthole die is proposed. The influences of extrusion ratio, welding chamber height, die core spacing and bearing length on the die core deflection are analyzed using Altair Inspire Extrude Metal finite element analysis software. The simulation results show that the influences of welding chamber height and die core spacing are significantly evident, whereas the influences of extrusion ratio and bearing length are weak. The maximum deformation of the die core increases with welding chamber height when it increases to a certain threshold. There is an optimum value for die core spacing, deviations from this value would promote die core deformation. The experimental results show that the micro heat pipe profile with a wall thickness dimensional accuracy of ±0.04 mm is obtained under the better die structure parameters. The corresponding main die structure parameters are extrusion ratio of 137, die core spacing of 28 mm, welding chamber height of 8 mm and bearing length of 3 mm.

Key words: micro heat pipe, porthole die, die optimization, aluminum alloy