The Benefits of the Hydroforming Process
Hydroforming was developed in the late 1940’s and early 1950’s to provide a cost effective means to produce relatively small quantities of drawn parts or parts with asymmetrical or irregular contours that do not lend themselves to stamping. Virtually all metals capable of cold forming can be hydroformed, including aluminum, brass, carbon and stainless steel, copper, and high strength alloys.
A hydroforming press operates like the upper or female die element. This consists of a pressurized forming chamber of oil, a rubber diaphragm and a wear pad. The lower or male die element, is replaced by a punch and ring. The punch is attached to a hydraulic piston, and the blank holder, or ring, which surrounds the punch.
The hydroforming process begins by placing a metal blank on the ring. The press is closed bringing the chamber of oil down on top of the blank. The forming chamber is pressurized with oil while the punch is raised through the ring and into the the forming chamber. Since the female portion of this forming method is rubber, the blank is formed without the scratches associated with stamping.
The diaphragm supports the entire surface of the blank. It forms the blank around the rising punch, and the blank takes on the shape of the punch. When the hydroforming cycle is complete, the pressure in the forming chamber is released and the punch is retracted from the finished part.
Tooling – With low volume runs, tooling is often the most important cost consideration. With hydroforming, a male die, or punch, and a blank holding ring are the only tools required as the rubber diaphragm and pressurized forming chamber act as the female die. As a result, hydroforming tooling is typically 50% less expensive than matched die tooling. With hydroforming, most punches are made from cast iron as opposed to the hardened tool steels used for match die drawing punches. Finally, hydroforming tools are easily mounted and aligned, making set-ups fast and efficient.
Development Costs – Proto-typing is often a necessary step in the manufacturing process. Changes in material type or wall thickness specifications can typically be accommodated with hydroforming without creating a need for new tooling.
Reduced Press Time – Complex parts requiring multiple press cycles in matched die operations can be drawn in a single hydroforming cycle. Hydroforming presses frequently achieve reductions of 60-70% compared to 35-45% for conventional matched die presses.
Finishing Costs – Aerospace, medical and commercial cookware applications often demand parts with outstanding surface finishes. Unlike matched die metal forming, which can leave scratches and stretch lines, the flexible diaphragm utilized in hydroforming eliminates surface blemishes, reducing the need for costly finishing processes like buffing.
Although hydroforming has numerous advantages over other matched die drawing, there are circumstances where deep draw stamping may be a better fit for your specific application. In addition to being one of the nation’s largest contract hydroformers, we also have deep draw stamping capability to 350 tons. Send us your drawings and our engineering oriented staff will explain the benefits of both metal forming processes and help select the most cost effective means to manufacture your parts.
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