What is Hydroforming


Hydroforming is a metal fabricating and forming process which allows the shaping of metals such as steel, stainless steel, copper, aluminum, and brass. This process is a cost-effective and specialized type of die molding that utilizes highly pressurized fluid to form metal. Generally there are two classifications used to describe hydroforming, sheet hydroforming and tube hydroforming. Sheet hydroforming uses one die and a sheet of metal; the blank sheet is driven into the die by high pressure water on one side of the sheet forming the desired shape. Tube hydroforming is the expansion of metal tubes into a shape using two die halves, which contain the raw tube. Hydroforming is used to replace the older process of stamping two part halves and welding them together. It is also used to make parts both more efficiently by eliminating welding as well as creating complex shapes and contours. Parts created in this method have a number of manufacturing benefits including seamless bonding, increased part strength, and the ability to maintain high-quality surfaces for finishing purposes.  
When compared to traditional metal stamped and welded parts, hydroformed parts are lightweight, have a lower cost per unit, and are made with a higher stiffness to weight ratio. The processes can also be utilized in the single stage production of components; saving labor, tools, and materials.  
PROCESS OVERVIEW  (See Illustration to right)
A simplified overview of the hydroform process.
  • a.) Raw tube is loaded into hydroforming dies.
  • b.) Hydroforming press closes. 
  • c.) The sealing rods engage the part, seal the ends and fill it with water pressure inside the part increases. 
  • d.) The sealing rods push the tube into the die (endfeed) and the internal pressure is ramped to its maximum value. 
  • e.) The hydroformed part takes on the shape of the die. 
  • f.) Final hydroformed part is removed.
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This before and after shows the expansion of the tube during the hydroform process. In the upper image, the tube, which has been bent in a previous step on a CNC bender, is placed into the hydroform die. The lower image shows the same tube after hydroforming. Note the expansion and odd shapes that the hydroformed tube took on.  

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