Patent ID: 6880377
Filing Date: 2005-04-19
Classification: B21D

Abstract:
1. A method of forming a sheet metal article from a blank of sheet metal that has been heated for stretch forming, said method being performed using a set of opposing tools, said tools comprising a punch having a surface defining a predetermined finish configuration for said article and a cavity tool having a cavity surface defining a preform configuration for said article, said method comprising: placing said blank between said opposing tools, said blank having a first side surface facing said cavity tool and a second side surface facing said punch; applying gas pressure to the second side surface of said blank to press said first side surface of said blank against said cavity surface, but not against said punch surface, to stretch and shape said blank into said preform configuration; moving said punch surface toward said blank in said preform configuration without contacting said blank; and applying gas pressure to said first side surface of said blank to push said first side of said blank from contact with said cavity surface and to press said second side surface against said punch surface, but not against said cavity surface, to further stretch and shape said blank from said preform configuration to said finish configuration.