For proponents of laser welding of automotive structures, Volkswagen AG is (1) to be admired or (2) a company that provokes tremendous jealousy. According to Dr. Klaus Loeffler, director, Joining Processes, Volkswagen AG (Wolfsburg, Germany), who spoke at the 12th annual Automotive Laser Applications Workshop organized by the University of Michigan, VW has been working with lasers on body-in-white applications since 1993, with the first production application occurring in '96 on a roof joint. In '97, three models had laser welded roof joints. Then, as time went on, there were more cars and more applications added to the mix. Today, the model that is without a doubt a laser-intensive vehicle is the Golf V, which, Loeffler said, has an astonishing 70 m of laser-welded joints on it. Nothing else comes close. Does this mean that spot welding has been eliminated from the Golf? No, Loeffler answered, there are still on the order of 1,400 spot welds on the vehicle (which is down from 4,608 spot welds on the Golf IV, which had just 1.4 m of laser welding)—as well as arc welds (7 m) and adhesives (30 m). He admitted that the Golf V was actually "more or less designed for spot welding," which means that when they move onto the next vehicles, they will be able to take further advantage of the structure-enhancing (the Golf V has 80% more static torsional stiffness, 15% more dynamic torsional stiffness, and 35% more dynamic bending stiffness than the model it replaces) and weight-saving (reduced flange widths facilitate sheet metal mass reduction) process. And it's not just welding that VW uses lasers for. There are also brazing and cutting performed on the Golf V. At the VW Wolfsburg plant, for example, there are 150 4-kW Nd:YAG lasers (sourced from Trumpf; http://www.us.trumpf.com/), one 1-kW Nd:YAG laser (also from Trumpf), 250 laser welding heads, and three laser cutting heads. Although the preponderance of lasers used by Volkswagen is in the Wolfsburg facility, Loeffler said that the equipment is used throughout the organization, regardless of whether the plants are in low- or high-cost areas. So you'll find them in places ranging from Belgium to South Africa.
The cars are being produced at 100 jobs per hour. Unquestionably, uptime is essential. But Loeffler said that uptime has not been a problem, estimating that it has been in excess of 99%. "Keep them clean and you'll get up time." It should be noted that the people who operate the equipment aren't a cadre of scientists and optical engineers, but people who were trained to run the equipment. Speaking of the importance of people to the smooth operations, Loeffler stated, "The people must feel that they own the system." Although he might be less than entirely objective on the subject, he described the laser processing as "the most reliable process we have in our plants." He added, "These are proven technologies."
One of the benefits of using laser systems for body welding is the fact that there is a tremendous amount of flexibility inherent in the equipment. For example, they have developed a framing station based on 14 lasers that not only welds (5,340 mm) and brazes (3,400 mm) the Golf, but is capable of handling VW vehicles ranging in size from the diminutive Lupo (a "three-liter" car, so called because it is supposed to be able to travel 100 km on that amount of fuel) to the Touareg sport utility vehicle (laser welding is also used on the Touareg's platform-mate, the Porsche Cayenne). The framing station requires 40% less floor space than a comparable spot welding setup. What's more, Loeffler pointed out that it is possible to use the laser generators for that station on a parallel station during the loading/fixturing/unloading of the first station, thereby taking advantage of the processing equipment.
Laser robots are employed along the main line. Loeffler said that just as they have standardized on 4-kW YAG lasers, they have also standardized on using laser heads that employ integrated fixturing (the fixturing types include: wheel, double wheel, splitter wheel, and single and double fingers). Here, too, an advantage is that the equipment facilitates handling different products or changes to existing products. In addition, changeover time from one model to another is minimized.
One of the issues in building a vehicle is tolerance stack. This is the same for the Golf as for any other car. Loeffler says this is being handled for the installation of the front end bumper module mounting plate by using a cell that takes an optical measurement of the auto body to determine the dimensions, then laser cuts the front rails to the required length before welding the plates in place. Loeffler described this as "the most amazing laser cell" in what is an unintentional understatement.
Although laser technologies are not inexpensive, according to Loeffler, there is an anticipated ROI of four years. And not only are they proliferating the number of lasers throughout VW—there are now more than 450, which puts the company well ahead of any other vehicle manufacturer—but Loeffler is looking toward the next generation of lasers. He's looking for such things as a 6-kW unit that has a resonator efficiency of 20%, a beam quality of 6 mm/mrad, flexible distribution of the beam through a cable of up to 100-m long, an uptime of 99.9%, and a maximum time to repair of 30 minutes.
Loeffler noted in passing, "I spend a lot of time cutting and welding plastics." Perhaps that may be the shape—or material—to come at VW.
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