| 摘要 |
PURPOSE:To reduce the number of working processes and to raise the productivity by forming a projection whose diameter is different from a body part from a blank obtained by cutting a rod material, subsequently, extruding the projecting part by backward extrusion, and finishing it in the shape of a pipe having a cavity in the body part. CONSTITUTION:A primary work 11 having a projection 12 whose diameter is different from a body part is formed by forward extrusion of a blank 10 obtained by cutting a rod material. Subsequently, a cavity is formed in the projecting part 12 of the work 11 by using a lower die 30 provided with a moving die 32 energized upward by a spring 33 and a counter-punch 36, and by backward extrusion by co-operation with a main punch 31, and a secondary work 13 which forms said part in the shape of a thin plate 14. In this regard, the work 13 is finished to a final product P by performing a machine work such as sizing, etc. In this way, it is possible to form parts by a simple die structure and also by reducing the number of working processes. |
