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Hydroforming (or hydramolding) is a cost-effective way of shaping malleable metals such as aluminum or brass 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.

[edit] 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).

[edit] Tube hydroforming

In tube hydroforming 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).

[edit] 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.

[edit] Examples of Hydroforming

Notable examples include:

• Satellite antennas up to 6 metres in diameter, such as those used in the Allen Telescope Array.^[1]
• The brass tube of Yamaha saxophones.^[2]
• The process has become popular for the manufacture of aluminium bicycle frames. The earliest commercially manufactured one being that of the Giant Manufacturing Revive bicycle^[3] first marketed in 2003.
• Many motor vehicles have major components manufactured using this technology, for example:
  • The technique is widely used in the manufacture of engine cradles.^[4] The first mass produced one was for the Ford Contour and Mystique in 1994.^[5] Others from a long list include the Pontiac Aztek,^[6] the Honda Accord^[7] and the perimeter frame around the Harley Davidson V-Rod motorcycle's engine.^[8]
  • As well as engine cradles, the main automotive applications for hydroforming are suspension, radiator supports and instrument-panel support beams.^[4] The first mass produced automotive component was in 1990 with the instrument panel support beam for the Chrysler minivan.^[5]
  • Various vehicle bodies and body components, the earliest mass produced one being the 1997 Chevrolet Corvette.^[9] A selection from many examples are the Ford F-150,^[9] 2006 Pontiac Solstice^[10] and the steel frame inside the John Deere HPX Gator Utility Vehicle.^[11]

[edit] 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.

[edit] References

1. ^ Weinreb, Sander (8-11 July 2003). "Low cost microwave ground terminals for space communication" (pdf) in 5th International symposium on reducing the cost of spacecraft ground systems and operations., Pasadena, CA: NASA. Retrieved on 2008-11-21. 
2. ^ "Saxophone factory tour". Yamaha Corporation. Retrieved on 2008-11-21.
3. ^ Quincy Liang (10 July 2008). "MIRDC VP Expects Hydroforming to Enable Vehicle Makers to Break the Mold", Taiwan Economic News. Retrieved on 5 December 2008. 
4. ^ ^{a b} "Use of USLAB technologies by automakers growing rapidly". American Iron and Steel Institute (2008). Retrieved on 2008-12-05.
5. ^ ^{a b} Harjinder Singh (2003). Fundamentals of Hydroforming. SME. pp. 4. isbn 9780872636620. http://books.google.co.uk/books?id=WcdZ83RrerYC&pg=PA4&lpg=PA4&dq=ip+beam&source=web&ots=jUhroNielY&sig=6EbF0r2sukSOaSRf8OFmTA348A8&hl=en&sa=X&oi=book_result&resnum=1&ct=result. 
6. ^ Tony Swan (July 2000). "2001 Pontiac Aztek - First Drive Review", Caranddriver.com. Retrieved on 5 December 2008. 
7. ^ Eric Lundin (24 July 2003). "Tier 1 supplier builds four-stage competitive strategy", The Fabricator. Retrieved on 5 December 2008. 
8. ^ "2009 Harley Davidson V-Rod Muscle". thekneeslider.com. Retrieved on 2008-12-05.
9. ^ ^{a b} "Hydroformed Frame Repairs", I-Car Advantage Online (13 September 2004). Retrieved on 5 December 2008. 
10. ^ "2006 Pontiac Solstice Sheetmetal Hydroforming Technology". The Auto Channel. Retrieved on 2008-12-05.
11. ^ "Utility Vehicle has hydroformed steel frame.", ThomasNet (5 December 2003). Retrieved on 5 December 2008. 

[edit] Links

• Pan Shocker:Americans patent pan plan

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