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Anna Kochan: European Associate Editor for Assembly Automation
As car design evolves, so do the manufacturing technologies. An area particularly affected by the latest developments in automotive design concerns assembly techniques, as participants at the recent ISATA conference in Florence heard.
Hydroforming is one of the emerging manufacturing technologies whose use is growing. In a typical application, hydroforming gives a weight saving of 10-15 per cent, says Dietmar Kay of Schafer Hydroforming, the German company which has just supplied a 20 million DM hydroforming system to Opel. The fully automated system is the most comprehensive hydroforming application anywhere in the world, he claims.
The Schafer hydroforming system at Opel's Bochum plant in Germany will make mild steel engine cradles for the new Astra (codenamed T3000). Engine cradles are conventionally made by welding two pressed parts together. Through the use of hydroforming, the Astra cradles will be formed from a hollow section blank, thus eliminating the weld and the flange necessary for the weld. Additional benefits are increased durability, fewer part numbers and lower production costs, Kay claims.
Kay explained the hydroforming process to the ISATA audience. The process, he said, requires a hydraulic press equipped with a two-piece die, two axial rams and a counter holder. The blank is first placed in the die. As the die closes around the blank, the open ends of the blank are "plugged" up by the two axial rams. Water is then injected into the blank and the pressure increased until it is sufficient to force the blank to deform and fill the die.
In the new Opel system, a 2.6m length of tube is turned into a fully finished engine cradle ready for assembly. After a pre-forming operation, the tube is passed to the hydroforming press. Here it is shaped and punched before going through a washing station and a final machining station where the cradle ends are finished. All parts handling is by six-axis Fanuc robots. When full production starts in January next year, the line will produce one million engine cradles a year, running on three shifts, five days a week, with only two operators in attendance.
Although few cars today incorporate any hydroformed parts, interest in the technology is growing. According to Kay, all the...