Method for hydroforming hollow profile metal workpieces

Abstract

A method for hydroforming hollow metal workpieces includes submerging the same in a reservoir of hydraulic fluid. A press is provided having a hydroforming station located within the reservoir and includes a forming cavity configured to receive the fluid filled workpiece and create a fluid cushion spaced between the outside of the workpiece and the inside of the forming cavity. Sealing mandrels supply high-pressure hydraulic fluid to the interior of the workpiece which hydroform the same to the shape of the final part. The outward flow of fluid from the fluid cushion space is controlled, along with the associated pressure, to maintain the fluid cushion at least until such time as the mandrel pushing step concludes, thereby alleviating friction and adhesion between the formed part and the forming cavity.

1 . A method for hydroforming hollow profile, metal workpieces using internal high-pressure hydraulics, comprising:
 submerging a hollow profile, metal workpiece in a reservoir of hydraulic fluid to substantially fill the hollow interior of the workpiece with hydraulic fluid;   providing a press having a top die, a bottom die and a hydroforming station disposed therebetween;   forming a forming cavity in the hydroforming station of the press at a location wholly within the reservoir, configured to receive therein the filled workpiece and create a fluid cushion space between the outside surface of the filled workpiece and the inside surface of the forming cavity;   transporting the filled workpiece through the reservoir into the forming cavity and creating a hydraulic fluid cushion in the fluid cushion space between the outside surface of the filled workpiece and the inside surface of the forming cavity;   pushing sealing mandrels against the ends of the filled workpiece disposed in the forming cavity;   hydroforming the filled workpiece in the forming cavity into the shape of the forming cavity to define a formed part by communicating high-pressure hydraulic fluid through at least one of the sealing mandrels with the interior of the filled workpiece in the forming cavity; and   controlling the outward flow of hydraulic fluid from the fluid cushion space and the associated pressure of the fluid cushion during said hydroforming step for maintaining the fluid cushion for a predetermined time period as hydraulic fluid flow into the interior of the filled workpiece decreases at least until such time as said mandrel pushing step has concluded, thereby alleviating friction and adhesion between the formed part and the forming cavity.   
     
     
         2 . A method for hydroforming workpieces as set forth in  claim 1 , wherein:
 said press providing step comprises providing a transfer press with at least one additional processing station; and including   transporting the filled workpiece from the additional processing station to the hydroforming station within the hydraulic fluid in the reservoir.   
     
     
         3 . A method for hydroforming workpieces as set forth in  claim 1 , wherein:
 said hydroforming step comprises pumping a volume of hydraulic fluid into the filled workpiece that is greater than can be accommodated in the filled workpiece in addition to the hydraulic fluid present in the filled workpiece.   
     
     
         4 . A method for hydroforming workpieces as set forth in  claim 2 , including:
 pre-forming the workpiece at the additional processing station to obtain a cross section configured for creating the fluid cushion between the outside surface of the filled workpiece and the inside surface of the forming cavity.   
     
     
         5 . A method for hydroforming workpieces as set forth in  claim 1 , wherein:
 when the forming cavity is in a closed condition, the top die displaces less than one twelfth of the quantity of fluid in which the bottom die is disposed.   
     
     
         6 . A method for hydroforming workpieces as set forth in  claim 1 , wherein:
 said hydroforming step includes selectively metering hydraulic fluid from the fluid cushion through a gap that has a defined width and is disposed in a separating gap between the top die and the bottom die.   
     
     
         7 . A method for hydroforming workpieces as set forth in  claim 1 , wherein:
 said hydraulic fluid flow controlling step includes selectively draining the hydraulic fluid cushion through grooves in the forming cavity which extend toward at least one of the sealing mandrels.   
     
     
         8 . A method for hydroforming workpieces as set forth in  claim 1 , including:
 heating the hydraulic fluid to a temperature greater than room temperature.   
     
     
         9 . A method for hydroforming workpieces, including:
 selecting the hollow profile metal workpiece from a material comprising aluminum, steel or magnesium alloy.