Die for extrusion of multi-hole tube and multi-hole tube made with the

Abstract

A multi-hole tube extrusion die comprises a female mold die having a flat opening and a mandrel having comb-teeth-like molding portions arranged in the opening. A heated material is extruded between the female mold die opening and the comb-teeth-like molding portions of the mandrel to form a tube having a multi-plicity of holes. An interval between each of the comb-teeth-like molding portions at the opposite ends of the mandrel and the comb-teeth-like molding portion adjacent to the outermost comb-teeth-like molding portion is set to be smaller than an intervals between the female mold die opening and each of the outermost comb-teeth-like molding portions and to be larger than an interval between adjacent ones of the other comb-teeth-like molding portions. Additionally, the outermost comb-teeth-like molding portions are larger in width than the other comb-teeth-like molding portions. Therefore, a lateral pressure difference acting on each of the outermost comb-teeth-like molding portions due to flows of the material is reduced, and the rigidity of outermost comb-teeth-like molding portions is increased, thereby preventing deformation of the die and enabling prolongation of the life of the die as well as a highly accurate extrusion.