Controlled material flow hydroforming

Abstract

A sheet metal blank positioned upon a lower die is wrapped around an upper die as the upper die is moved down to a closed position by an outer slide, the blank being clamped between the upper and lower dies whereby the periphery of the blank is gripped between a male and female bead mounted all around a part print cavity in the upper and lower dies, respectively. The outer slide then dwells while an inner slide moves down, engaging and actuating cylinder assemblies, causing hydraulic fluid to be forced into a region between the clamped blank and the lower die, the blank being formed into a part print cavity defined in the upper die. The male bead exerts varying control on the sheet to allow it to stretch across portions of the cavity while flowing into other portions of the cavity. A locking mechanism prevents the bending of the dies and holds the dies in a closed position thereby assisting the engagement of the male bead with the female bead. As a safety feature, the mechanism is configured to automatically open when the die cavity is moved up. The locking mechanism allows the use of high pressures to make large parts, such as car hoods, doors, deck lids, and quarter panels in conventional currently available double action presses.