| 摘要 |
PROBLEM TO BE SOLVED: To light a weight, reduce cost, and ensure strong joining force and a high joining accuracy by molding a cylindrical parts by means of a rear-extrusion method from a raw material which is formed in the same outer peripheral shape as the cylindrical parts, and which is provided with a penetrating hole having the same diameter as a small diameter part of an axial parts on a center part. SOLUTION: In a raw material 12, its outer peripheral shape 13 is formed in the nearly same shape as an outer peripheral shape 9 of a cylindrical part 4 of a cylindrical parts 2 as a product, and a penetrating hole 14 having the nearly same diameter as a small diameter part of an axial parts joined later is provided on the center part. A punch of a mold structure for rear-extrusion molding the raw material 12 has the nearly same shape as an inner circumferential shape 10 of the cylindrical parts 2 on the way thereof, and has a round shape part having the nearly same diameter as that of the penetrating hole 11 on a tip end part. At the time of molding, a material also flows in the cylindrical part 28 side, a molding load is reduced comparing with normal molding, a molding load is sharply reduced by the penetrating hole 14, a molding life is improved, and cost is reduced. The inner circumferential shape 10 and the penetrating hole 11, an outer periphery 31 of the cylindrical part 28 and a lower end surface 32 are molded with a good accuracy, they are joined with the axial parts with a good accuracy, and joining strength is quite strengthened in the case where a pipe material or a plate material are used as the raw material in the cylindrical part 28.
|
