Method for vaccum assisted preforming of superplastically or quick plastically formed article

A method of preforming and forming a sheet metal article from a blank of sheet metal that has been heated for stretch forming, the method being performed using a set of opposing dies including a punch having a punch surface defining a predetermined final configuration for the article and a cavity die having a cavity surface defining a preform configuration for the article, the method comprising:

• placing the blank between the spaced apart opposing dies, the blank having a first side surface facing the cavity die and a second side surface facing the punch die;
• binding the blank to the cavity die in gas tight relation therewith;
• applying a vacuum to the first side of the blank to stretch and shape the blank to a preform configuration that conforms generally to the cavity surface;
• closing the punch and the cavity die toward one another so that the punch die contacts a part of the second surface of the blank to assist the vacuum in shaping the blank to the preformed configuration;
• and applying gas pressure to the first side surface of the blank to press the second side surface against the punch surface, to further shape the blank to the finish configuration.

A method of preforming and forming a sheet metal article having a raised area region requiring a deep draw of a blank of sheet metal, the method comprising:

• providing a punch die having a punch surface over which the blank is to be stretched to define the final configuration of the article, the punch die including a crown portion to define the raised area region;
• providing a cavity die that opposes the punch die and having a cavity surface that defines a preform configuration of the article, including a deep draw cavity recess portion that registers with the crown portion of the punch die;
• placing a preheated blank between the spaced apart opposing dies, the blank having a first side surface facing the cavity die and a second side surface facing the punch die;
• binding the blank to the cavity die in gas tight relation therewith;
• applying a vacuum to the first side of the blank to stretch and shape the blank to a preform configuration that conforms generally to the cavity surface and deep draws the blank into the deep draw cavity recess of the cavity die;
• closing the punch die and the cavity die toward one another;
• and applying high gas pressure to the first side surface of the blank to press the second side surface against the punch surface, to form and shape the preformed blank to the finish configuration including forming of the blank over the crown portions of the punch die.