US 6,886,383 B2Granted

Method for stretch forming sheet metal by pressing and the application of gas pressure

AssigneeGeneral Motors Corporation

InventorsChongmin Kim, Gary A. Kruger, Mark G. Konopnicki, Richard Murray Kleber, Michelle R. Goff

Life of this patent

Estimating the term…

Loading patent…

Abstract

A method is disclosed for forming sheet metal articles, such as automotive body panels, having significant curvatures in front-to-back and side-to-side directions. Opposing, complementary, preforming and final shape forming tools are used in a single press. A sheet of superplastically or quick plastically formable sheet metal alloy, heated to a forming temperature, is first stretched against the preform tool by the final shape tool to form a preform that has experienced most of the metal stretching required for the final part shape. The preform is removed from the preform tool and formed against the opposing, final shape tool with pressurized gas to obtain the final sheet metal part shape.

Claims16

Dependent claims

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 punch 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 a 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;
pressing said punch against the second side surface of said sheet to push the first side surface of said sheet against said cavity tool surface to stretch and shape said blank in a sheet metal preform configuration that does not conform fully to either said cavity surface or said punch surface;
and
applying gas pressure to said first side surface of said blank to press said second side surface against said punch surface, but not against said cavity surface, to shape said blank from said sheet metal preform configuration to said finish configuration.

1 more element

A method of forming an article from a blank of sheet metal of a composition and metallurgical microstructure for high elongation stretch forming, said blank having been heated to a temperature for said stretch forming, said method being performed using opposing tools, said tools comprising a punch having a punch 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 a said blank between said opposing tools, said tools then being in an open position, said blank having a first side surface facing said cavity tool and a second side surface facing said punch;
pressing said punch against the second side surface of said sheet to push the first side surface of said sheet against said cavity tool surface to stretch and shape said blank in a sheet metal preform configuration that does not conform fully to either said cavity surface or said punch surface;
and then
applying gas pressure to said first side surface of said blank to press said second side surface against said punch surface, but not against said cavity surface, to shape said blank from said sheet metal preform configuration to said finish configuration.

1 more element

Dependencies are inferred from the claim text.