Patent ID: 6415638
Filing Date: 2002-07-09
Classification: B21D

Abstract:
Method of forming a tubular work into a shaped hollow product by using hydroforming process, comprising:preparing female and male dies, said female die having a longitudinally extending cavity which has a polygonal cross section when receiving said male die; placing said tubular work in said cavity of the female die; feeding the interior of said tubular work with a hydraulic fluid; increasing the pressure of the hydraulic fluid to a given level, said given level being less than a critical level that causes a bulging of said tubular work; pressing said male die against said tubular work to deform the same while keeping the hydraulic fluid at said given level, thereby forming a shaped hollow product that has a polygonal cross section that conforms to that of said cavity; and continuing the pressing by the male die until a circumferential length of said shaped hollow product becomes shorter than that of said tubular work.