Hydroforming (or hydramolding) is a cost-effective way of shaping malleable metals such as aluminum into lightweight, structurally stiff and strong pieces. One of the largest applications of hydroforming is the automotive industry, which makes use of the complex shapes possible by hydroforming to produce stronger, lighter, and more rigid unibody structures for vehicles. This technique is particularly popular with the high-end sports car industry and is also frequently employed in the shaping of aluminium tubes for bicycle frames.

Hydroforming is a specialized type of die forming that uses a high pressure hydraulic fluid to press room temperature working material into a die. To hydroform aluminum into a vehicle's frame rail, a hollow tube of aluminum is placed inside a negative mold that has the shape of the desired end result. High pressure hydraulic pistons then inject a fluid at very high pressure inside the aluminum which causes it to expand until it matches the mold. The hydroformed aluminum is then removed from the mold.

Hydroforming allows complex shapes with concavities to be formed, which would be difficult or impossible with standard solid die stamping. Hydroformed parts can often be made with a higher stiffness to weight ratio and at a lower per unit cost than traditional stamped or stamped and welded parts.

This process is based on the 1950s patent for hydramolding by Milton Garvin of the Schaible Company of Cincinnati, OH. It was originally used in producing kitchen spouts. This was done because in addition to the strengthening of the metal, hydramolding also produced less "grainy" parts, allowing for easier metal finishing.

Sheet hydroforming

In sheet hydroforming there is Bladder forming (where there is a bladder that contains the liquid, no liquid contacts the sheet) and hydroforming where the fluid contacts the sheet (no bladder).

Tube hydroforming

In tube hydrforming there are two major practices: high pressure and low pressure: Under high pressure the tube is fully enclosed in a die prior to presurization of the tube. In low pressure the tube is slightly pressurized to a fixed volume during the closing of the die (used to be call the Variform process).

Explosive Hydroforming

Industrial hydroforming machines use a piston to generate pressure in the hydraulic fluid used in hydroforming, but an experimental alternative is the use of explosives to generate the pressure. Called explosive hydroforming, this method places an explosive charge, with or without an additional working fluid, on the high pressure side of the material. When the explosive is detonated, the pressure forces the working material into the die, at pressures of up to millions of pounds per square inch. See also explosive welding, which allows metals of different types to be bonded at an atomic level. Since both explosive hydroforming and explosive welding use similar techniques, it is possible to combine the two methods to both shape and weld metals simultaneously.

Examples of Hydroforming

Popular vehicles that utilize this technology:

• Ford F-150 (2004-Current) Fully-boxed hydroformed frame
• Dodge Durango
• Dodge RAM Light Duty and Heavy Duty (2002-2005) and (2005-Current)
• Pontiac Aztek (GMT250) Engine cradle
• 5th generation Chevrolet Corvette (1997-2004)
• 6th generation Chevrolet Corvette (2005-Current)
• Modern Aston Martin vehicles such as the DB7
• 2006+ Pontiac Solstice
• 2006 LTI TX4 London Black Cab
• 2006 Saturn Sky
• 2006 Subaru Impreza
• 2003+ Ford Crown Victoria, Mercury Grand Marquis, and Lincoln Town Car
• Harley Davidson V-Rod motorcycle
• Mountain Cycle San Andreas Mountain Bike
• 2007 John Deere HPX Gator Utility Vehicle
• 1999+ GM GMT800/GMT900 Series Truck (Silverado, Sierra) Frames
• Maverick mountain bikes Maverick Bike, www.maverickbike.com
• Marin Bicycle
• Trek Bicycle
• Santa Cruz Bicycles

Hydroforming is also used to form satellite antennas up to 6 meters in size. Such antennas are used, for example, in the Allen telescope array.

Controversy

Hydroforming is also used in the construction of non-transportation items. Notable among these is a patent controversy in the use of the process to produce steel drums. A pair of US inventors applied for a patent using this process, but it is accepted that Trinidad and Tobago Instruments Ltd. had used this process previously in the production of steel drums.

References

Links

http://www.trinicenter.com/Terryj/2002/Apr/162002.htm Pan Shocker:Americans patent pan plan