Advanced sealing system to prevent leakage in hydroforming

Tube hydroforming is a metal forming technology that uses internal pressure and the axial feeding force to fabricate products with complicated cross-sectional geometries. In this study, an advanced sealing system is proposed to prevent leakage during the hydroforming process. The advanced sealing system is composed of a die spring, cylindrical sleeve and punch with end fillet. The improved sealing effect originates from the increased contact because of the axial force of the punch and reaction force of the spring caused by the punch. When the proposed sealing system is used, the circumference of the tube end becomes more tightly sealed by the axial pressure between the punch and sleeve, and the axial pressure increases with increasing axial feeding. The effects of the advanced sealing system on the effectiveness of the contact between the tube end and punch were further analyzed with finite element method. The feasibility of the proposed sealing system is experimentally confirmed by hydroforming a non-axisymmetric complicated part.