Patent ID: 8621904

Claim:
A hydroforming apparatus comprising a mold, an axial pushing means, an internal pressure means for applying internal pressure to a metal tube set in the mold to form the metal tube into a predetermined shape, contact sensors configured to sense contact with the metal tube positioned at two or more different positions in the tube axial direction inside said mold at locations not contacting said metal tube when said metal tube is first set in the mold and optionally at locations no longer in contact with the mold during hydroforming, and a control means for controlling the axial pushing action and the internal pressure by sensing contact of said mold and said metal tube obtained by said contact sensors, said control means being configured to perform a first step of axially pushing tube ends while holding the internal pressure at a constant value, and stopping the axial pushing when among the contact sensors not yet in contact with said metal tube when the metal tube is first set in the mold, the contact sensors mounted at positions closest to the tube ends sense contact with the metal tube, a second step of raising only the internal pressure while leaving the positions of the tube ends fixed, and stopping the increase in the internal pressure when at least one of the sensors not yet in contact with the metal tube senses contact, and a third step of lowering the internal pressure to the constant value of the first step while leaving the positions of the tube ends fixed, and repeating the first step to third step until all of the contact sensors sense contact.