Patent ID: 6619094
Filing Date: 2003-09-16
Classification: B21D

Abstract:
A method of forming a metal sheet comprising:arranging a metal sheet on a contoured mold surface of a drawing mold; providing heated pressurized air through at least one air hole in said mold surface so as to form an air cushion between said mold surface and said metal sheet, and varying a pressure and a temperature of said heated pressurized air; and applying a mechanical drawing tension to said metal sheet arranged on said mold surface with said air cushion therebetween, so as to draw and deform said metal sheet on said mold, wherein said varying of said pressure and said temperature of said heated pressurized air, and said applying of said mechanical drawing tension comprise the following phases: a heating phase which includes heating said pressurized air to a heating temperature above room temperature and providing said pressurized air at a first constant pressure above atmospheric pressure to form said air cushion, whereby said metal sheet is heated to said heating temperature, without drawing and deforming said metal sheet during said heating phase; a deforming phase which takes place after said heating phase and which includes maintaining said pressurized air at said heating temperature and providing said pressurized air at a second constant pressure above said first constant pressure to form said air cushion, and applying said mechanical drawing tension so as to draw and deform said metal sheet from a first condition to a second condition during said deforming phase; and a cooling phase which takes place after said deforming phase and which includes cooling said pressurized air down to room temperature and providing said pressurized air at a third constant pressure above atmospheric pressure and below said second constant pressure, whereby said metal sheet is cooled down from said heating temperature, without further drawing and deforming said metal sheet so that said metal sheet maintains said second condition during said cooling phase.