US Patent 7313939 Hydroforming machine and a method of hydroforming

A hydroforming machine characterized by a die 2 having an opening on the upper surface and a fluid tank 2a filled with fluid, a holder 3 being able to hold a periphery part between the die 2 and itself, a punch 4 being movable in a direction into or out for the fluid tank 2a, and a pressure controller 5 controlling the fluid pressure in the fluid tank 2a according to the position of the punch 4.