Elevated temperature forming method and preheater apparatus

Abstract

An elevated temperature forming system in which a sheet metal workpiece is provided in a first stage position of a multi-stage pre-heater, is heated to a first stage temperature lower than a desired pre-heat temperature, is moved to a final stage position where it is heated to a desired final stage temperature, is transferred to a forming press, and is formed by the forming press. The preheater includes upper and lower platens that transfer heat into workpieces disposed between the platens. A shim spaces the upper platen from the lower platen by a distance greater than a thickness of the workpieces to be heated by the platens and less than a distance at which the upper platen would require an undesirably high input of energy to effectively heat the workpiece without being pressed into contact with the workpiece.

What is claimed is: 
     
         1 . A method for fabricating deep drawn panels from sheet metal workpieces having insufficient formability at lower temperatures, the method including the steps of:
 providing a first sheet metal workpiece in a first stage position of a multi-stage pre-heater;   heating the first workpiece to a first stage temperature lower than a desired pre-heat temperature;   moving the first workpiece to a final stage position of the multi-stage preheater;   heating the first workpiece to a desired final stage temperature;   transferring the first workpiece to a forming press;   actuating the forming press to form the first workpiece.   
     
     
         2 . The method of  claim 1  in which the step of transferring the first workpiece to a forming press includes transferring the first workpiece to a heated forming press. 
     
     
         3 . The method of  claim 1  including the additional steps of:
 cooling the first workpiece after forming the first workpiece; and 
 performing an operation on the first workpiece selected from the group of operations consisting of trimming, piercing, and flanging. 
 
     
     
         4 . The method of  claim 1  in which the steps of moving the first workpiece to a final stage position of the multi-stage preheater and heating the first workpiece to the desired final stage temperature include:
 providing a second sheet metal workpiece in the first stage position of the multi-stage pre-heater; and 
 heating the second workpiece in the first stage position to a first stage temperature. 
 
     
     
         5 . The method of  claim 1  in which the steps of moving the first workpiece to a final stage position of the multi-stage preheater and heating the first workpiece to the desired final stage temperature include:
 moving the first workpiece to a second stage position of the multi-stage preheater after the step of heating the first workpiece to a first stage temperature; 
 heating the first workpiece in the second position to a second stage temperature greater that the first stage temperature and less than a final stage temperature; 
 moving the second workpiece to the second stage position after the step of heating the second workpiece to a first stage temperature; 
 heating the second workpiece in the second stage position to a second stage temperature; 
 providing a third sheet metal workpiece in the first stage position; and 
 heating the third workpiece in the first stage position to a first stage temperature 
 
     
     
         6 . The method of  claim 1  in which the step of transferring the first workpiece to a forming press includes transferring the first workpiece to a forming press as a second workpiece is moved to the final stage position. 
     
     
         7 . The method of  claim 1  in which the step of actuating the forming press to form the first workpiece includes actuating the forming press to form the first workpiece as a second workpiece is being heated in the final stage position of the preheater to a final stage temperature. 
     
     
         8 . The method of  claim 1  including the additional step of heating at least a portion of the press before the step of actuating the forming press to form the first workpiece. 
     
     
         9 . The method of  claim 3  in which the step of cooling the workpiece includes blowing air over the workpiece.