DESIGN METHOD FOR EXTRUSION DIE

PROBLEM TO BE SOLVED: To provide a design method for an extrusion die capable of obtaining an extrusion material having no crack with less strain. SOLUTION: A design method is provided for determining the opening area of an introduction hole to form a hollow molded material having a prescribed shape. A measuring die has the through-holes which have the same opening shape, opening area and are arranged with the same depth as the introduction holes corresponding thereto and which distribute symmetrically around the axial center in the introduced direction of a material body. First, the respective lengths of rods extruded from the through-holes of the measuring die are measured, the ratio of the length of peripheral rods to that of central rod is calculated, and the distribution curve of rod length ratio in the measuring die is drawn up as a base to set up the axial center position of each introduction hole of the extrusion die to be used for actual production and the opening area of the introduction hole positioned at the center of the extrusion die. The axial center positions of the introduction holes surrounding the set hole are searched on the basic curve, and then based on the rod length ratio corresponding to the axial center position on the basic curve, the opening areas of the peripheral holes are calculated. COPYRIGHT: (C)2008,JPO&INPIT