Hydroformed chassis article interesting
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Hydroformed chassis article interesting
Automakers around the world are reaping benefits from a fascinating metalworking technology that before now has been used mainly to produce unglamorous household items like plumbing fixtures and doorknobs. Pioneered in Germany more than half a century ago, hydroforming is starting to replace traditional stamp-and-weld processes in the manufacture of steel frames and body parts for cars and light trucks. Optimists believe hydroforming--so named because it molds parts with highly pressurized water--may even become the principal method for crafting a vehicle's bones. Think of a kid inflating a novelty balloon with water, but make it of metal and blow it up inside a mold using great force. That's hydroforming.
The auto industry has long built the structures that give vehicles their strength by stamping sheets of steel into the proper shapes on giant presses and then welding the pieces together. That's no longer how it's done with the Chevrolet Corvette, which contains the largest vehicle parts produced so far by hydroforming. GM uses the process at a plant in Pontiac, Mich., to make the Corvette's 15-foot-long "frame rails"--a pair of curvy beams that run from bumper to bumper. The frame rails of the previous model, which went out of production in 1996, were stamped in 14 separate sections and then welded together in a far more elaborate process. Not only has hydroforming saved GM $25 million in tooling costs for the Corvette, but it also produces parts that are much stiffer than those made by traditional methods, improving the car's handling. While most applications of hydroforming don't save quite as much money, the benefits are attractive enough to have made converts of DaimlerChrysler, which will use the process in its 2002 Dodge Ram pickup, and Harley-Davidson, which incorporates hydroformed parts in its new V-Rod motorcycle.
Still, no automaker uses more water-molded metal than GM. Since its engineers first began looking at hydroforming in a serious way in the mid-1980s, they have amassed 25 hydroforming patents and a wealth of design and process wisdom. The Corvette is a relatively low-volume car, with a production run of only about 35,000 units per year. But GM is also using hydroformed frame sections in one of its money-spinning bestsellers, the T800 series of full-sized pickups, including the Chevy Silverado and GMC Sierra. With annual production of more than 1.5 million trucks, the T800 family is the highest-volume application of hydroforming in the world.
Magna Structural Systems' million-square-foot complex in St. Thomas, Ontario, is a good place to see hydroforming in action. More than 900 robots tend a maze of machinery at the plant, which is dedicated to making frames for GM light trucks. When it won the contract to build the ladder-like frame for the T800, Magna was the only supplier willing to try hydroforming large parts at high volumes. Magna is using the process to create the frame's complex front section, which incorporates critical mounting points for the engine and front suspension. GM designed the section to be producible by traditional methods too--just in case. But Magna's engineers, working with machinery builder SPS Siemplekamp of Krefeld, Germany, developed six big presses now bending metal at full tilt using water pressurized to thousands of pounds per square inch.
In the plant's vast hydroforming area, materials-handling robots deliver a tubular-steel "blank" to automatic bending equipment that kinks the piece to approximate the jogs of the finished part. After a brief inspection by laser, robots load the bent tube into the lower half of a hydroforming die. The die halves then clamp together under great hydraulic force while fixtures inject pressurized water into the open ends of the tube. As the tube balloons into the cavities of the die, the fixtures push inward at each end, forcing more metal into the die. The result is a finished part with constant wall thickness and none of the thin spots that can make stamped parts weak. At the same time, punches built into the inner surface of the die pierce holes that will be used for attaching the truck's front suspension and defining its wheel alignment. The whole process takes 20 seconds.
After the die halves unclamp, another robot delivers the part to a laser-cutting system that trims the ends neatly. The laser cutter also makes holes for mounting components like springs and steering gear. Then the front section is sent downstream to be joined to the middle and rear sections of the frame rail. "One of our proudest successes is the dimensional stability of our frames," says Scott Turner, Magna's vice president for business and finance.
The auto industry has long built the structures that give vehicles their strength by stamping sheets of steel into the proper shapes on giant presses and then welding the pieces together. That's no longer how it's done with the Chevrolet Corvette, which contains the largest vehicle parts produced so far by hydroforming. GM uses the process at a plant in Pontiac, Mich., to make the Corvette's 15-foot-long "frame rails"--a pair of curvy beams that run from bumper to bumper. The frame rails of the previous model, which went out of production in 1996, were stamped in 14 separate sections and then welded together in a far more elaborate process. Not only has hydroforming saved GM $25 million in tooling costs for the Corvette, but it also produces parts that are much stiffer than those made by traditional methods, improving the car's handling. While most applications of hydroforming don't save quite as much money, the benefits are attractive enough to have made converts of DaimlerChrysler, which will use the process in its 2002 Dodge Ram pickup, and Harley-Davidson, which incorporates hydroformed parts in its new V-Rod motorcycle.
Still, no automaker uses more water-molded metal than GM. Since its engineers first began looking at hydroforming in a serious way in the mid-1980s, they have amassed 25 hydroforming patents and a wealth of design and process wisdom. The Corvette is a relatively low-volume car, with a production run of only about 35,000 units per year. But GM is also using hydroformed frame sections in one of its money-spinning bestsellers, the T800 series of full-sized pickups, including the Chevy Silverado and GMC Sierra. With annual production of more than 1.5 million trucks, the T800 family is the highest-volume application of hydroforming in the world.
Magna Structural Systems' million-square-foot complex in St. Thomas, Ontario, is a good place to see hydroforming in action. More than 900 robots tend a maze of machinery at the plant, which is dedicated to making frames for GM light trucks. When it won the contract to build the ladder-like frame for the T800, Magna was the only supplier willing to try hydroforming large parts at high volumes. Magna is using the process to create the frame's complex front section, which incorporates critical mounting points for the engine and front suspension. GM designed the section to be producible by traditional methods too--just in case. But Magna's engineers, working with machinery builder SPS Siemplekamp of Krefeld, Germany, developed six big presses now bending metal at full tilt using water pressurized to thousands of pounds per square inch.
In the plant's vast hydroforming area, materials-handling robots deliver a tubular-steel "blank" to automatic bending equipment that kinks the piece to approximate the jogs of the finished part. After a brief inspection by laser, robots load the bent tube into the lower half of a hydroforming die. The die halves then clamp together under great hydraulic force while fixtures inject pressurized water into the open ends of the tube. As the tube balloons into the cavities of the die, the fixtures push inward at each end, forcing more metal into the die. The result is a finished part with constant wall thickness and none of the thin spots that can make stamped parts weak. At the same time, punches built into the inner surface of the die pierce holes that will be used for attaching the truck's front suspension and defining its wheel alignment. The whole process takes 20 seconds.
After the die halves unclamp, another robot delivers the part to a laser-cutting system that trims the ends neatly. The laser cutter also makes holes for mounting components like springs and steering gear. Then the front section is sent downstream to be joined to the middle and rear sections of the frame rail. "One of our proudest successes is the dimensional stability of our frames," says Scott Turner, Magna's vice president for business and finance.
