Patent ID: 7225542

Claim:
A method of manufacturing a vehicle body compartment lid, the method comprising: providing a unitary panel having a first portion formed as a vehicle body compartment lid outer panel and a second portion formed as a vehicle body compartment lid inner panel; and bending the panel to form a crease between the first portion and the second portion; wherein the method further comprises forming a sheet to produce the panel; wherein said forming the sheet includes placing the sheet in its substantially unformed, flat state between first and second die members movable between a die open position, for insertion of said sheet in its flat state and removal of the formed panel, and a die closed position in which said dies sealingly engage the periphery of said sheet for stretch forming of the die enclosed area of the sheet utilizing differential gas pressure, said first die member having a forming surface and defining a cavity between said forming surface and a first surface of said sheet, said second die having a sheet metal shaping surface opposite said cavity, said dies being in said die open position and said sheet being positioned between said preform surface and said cavity; heating said sheet to a stretch forming temperature; moving said dies to their closed position such that said first die engages the periphery of said sheet and pulls the heated sheet against said second die shaping surface to draw sheet material into said cavity so that said sheet is no longer flat and more sheet material is disposed within its sealingly engaged periphery than if the sheet had remained flat; and applying gas pressure to the second side of said sheet to stretch the sheet into conformity with said first die forming surface.