Method of designing and forming a sheet metal part

Abstract

A method of forming a part and a method of designing a part to be formed from a sheet metal blank is disclosed. The part may be formed from lightweight high-strength material to an extent that would normally exceed the forming limits of the material if the part were attempted to be formed in one step in a multi-part die set. Critical areas including deep pockets and sharp radius areas of the final part are formed from a preform or intermediate shape part. The preform is further formed in a fluid pressure forming process to a final part shape wherein broad radius areas of the preform are formed into deep pockets and sharp corners.

1 . A method of forming a part from a sheet metal blank, wherein the part has at least one critical region that is formed to a final design shape, the method comprising:
 drawing the blank to form an intermediate shaped part that includes at least one bulge adjacent to the critical region;   forming the intermediate shaped part to form the at least one bulge into the critical region to form the final design shape.   
   
   
       2 . The method of  claim 1  wherein the forming step is performed in a fluid pressure forming process. 
   
   
       3 . The method of  claim 1  wherein the critical regions are areas of the final design shape that require drawing the blank into a sharp corner that exceeds the forming limits of the blank. 
   
   
       4 . The method of  claim 1  wherein the critical regions are areas of the final design shape that require drawing the blank to a depth that exceeds the forming limits of the blank. 
   
   
       5 . The method of  claim 1  wherein in the drawing step the blank is drawn to a depth that is within the forming limits of the blank, and wherein the step of forming the part to the final design shape results in forming a part that would exceed the forming limits of a single step process. 
   
   
       6 . The method of  claim 1  wherein the intermediate shaped part has at least one bulge and an increased radius critical region and wherein the intermediate shaped part has substantially the same surface area compared to the surface area of the final part shape. 
   
   
       7 . The method of  claim 1  wherein an intermediate cavity defined by the intermediate part shape is within a boundary of a final cavity defined by the final part shape. 
   
   
       8 . The method of  claim 1  wherein the drawing operation is performed in a stamping die set that has at least two dies. 
   
   
       9 . A method of designing a part to be formed from a sheet metal blank comprising:
 defining a final part shape as a computer aided design model;   analyzing the final part shape using finite element analysis;   identifying critical regions in the final part shape where forming limits of the sheet metal blank are approached or exceeded;   simulating a design shape to locally reduce the strain applied to the blank in developing an intermediate part shape based upon the shape of the final part, wherein the surface area of the intermediate part shape and the final part shape are substantially the same.   
   
   
       10 . The method of designing a part of  claim 9  wherein an intermediate cavity defined by the intermediate part shape is within a boundary of a final cavity defined by the final part shape. 
   
   
       11 . The method of designing a part of  claim 9  wherein in the analysis step finite element analysis is used to determine nodal forces in the critical regions and imposing the nodal forces required to transform the final design shape into the intermediate shape in the step of simulating the design shape. 
   
   
       12 . The method of designing a part of  claim 9  wherein in the step of simulating the design shape the final part shape is elastically deformed to develop the intermediate part shape so that the surface area relationship of the intermediate part shape and the final part shape is maintained and the intermediate shape is within the final part shape. 
   
   
       13 . The method of designing a part of  claim 9  wherein at least one bulge of the blank is designed to be formed in the intermediate part shape that is reformed to form the at least one bulge into a deep cavity. 
   
   
       14 . The method of designing a part of  claim 9  wherein at least one bulge is designed to be formed in the intermediate part shape that is reformed to form the at least one bulge into a sharp corner. 
   
   
       15 . The method of designing a part of  claim 9  wherein the intermediate part shape is developed in an iterative process wherein at least one bulge is designed to be added in at least one critical region, and further comprising testing the final part to verify that forming limits are not exceeded to form the final part. 
   
   
       16 . A method of designing a part to be formed from a sheet metal blank comprising:
 defining a final part shape as a computer aided design model;   analyzing the final part shape using finite element analysis;   identifying critical regions in the final part shape where forming limits of the sheet metal blank are approached or exceeded;   simulating a design shape to locally reduce the strain applied to the blank in developing an intermediate part shape based upon the shape of the final part, wherein an intermediate cavity defined by the intermediate part shape is within a boundary of a final cavity defined by the final part shape.   
   
   
       17 . The method of designing a part of  claim 16  wherein the step of simulating the design shape further comprises elastically deforming the final part shape in the simulation to develop the intermediate part shape so that the surface area relationship of the intermediate part shape and the final part shape is maintained. 
   
   
       18 . The method of designing a part of  claim 16  wherein at least one bulge of the blank is designed to be formed in the intermediate part shape that is reformed to form the at least one bulge, wherein the at least one bulge is formed into the critical region. 
   
   
       19 . The method of designing a part of  claim 16  wherein the intermediate part shape is developed in an iterative process wherein at least one bulge is designed to be added in at least one critical region, and further comprising testing the final part to verify that forming limits are not exceeded to form the final part. 
   
   
       20 . The method of designing a part of  claim 16  wherein the forming step is performed in a fluid pressure forming process.