Automotive welding evolves with new processes, equipment
July 25, 2002
Automakers are constantly trying to improve automotive designs, making vehicles lighter and stronger, using thinner materials, and redesigning points of strength for better crash resistance. At the same time, welding equipmentmakers who serve the industry are focusing on this quest for quality by developing the equipment to weld hydroformed parts, aluminum, and coated materials: critical components that affect how vehicles are made today.
It's been ages since horse-drawn carriages routinely transported passengers. In today's world, bypasses and interstates weave paths across the country, and many of the classic cars we see on the road are being carted from one classic-car show to the next instead of used as everyday vehicles.
Even the Corvette® has changed in the last 25 years. Corvettes are just one example of how the body of the automobile has changed. Not only are automobile bodies less angular and more aerodynamically rounded in general, but Corvettes, for instance, use more aluminum today than they did 30 years ago. Then they were made with steel.
But changes in the automotive industry aren't limited just to what's under the hood or the body frame. They also affect the welders, welding processes, and welding equipment used to make the vehicles we drive and ride in every day.
Three critical components affect how cars are made today, according to Carl Occhlialini, manager of Lincoln Electric Co.'s automotive group, Southfield, Mich. (www.lincolnelectric.com). Occhlialini and the automotive group introduce new technologies to corporate welding engineers at auto manufacturing facilities.
Hydroformed Parts."Hydroformed tubes are being used for side beams for frames on cars and trucks," Occhlialini said. "Sometimes it sets up joints that have varying thicknesses and fit-up and are difficult to weld." The answer, he said, is to use software-driven, computer-based power sources that control the current and heat input better than conventional units, therefore providing improved gap-filling capabilities for more uniform welds.
Coated Materials."Hydroformed parts tend to vary in thickness," Occhlialini said, so these materials are coated as an added barrier to corrosion. Zinc is a component of these coatings, making welding with conventional solid wires more difficult. Occhlialini noted that cored wires offer specific benefits because they have fluxes in their core that react to the zinc in a way that creates better welds that are higher in quality.
Aluminum."The price of aluminum has been volatile and variable," Occhlialini said, explaining that this makes planning to build a car difficult. Currently, however, the price of aluminum is remaining more constant, so automakers don't have to be as concerned with price fluctuations when they're designing a new model, he said.
New Technology."Before, we used constant voltage-type welding equipment that made it difficult to make small welds. Welds made larger than necessary cause excess distortion, burn-through, and spatter, all of which add to the costs of welding. To resolve these problems, we turned to more expensive gases," Occhlialini said.
But the story doesn't end there. Automakers are challenged on many other fronts—the biggest being cost, according to welding equipmentmakers who focus on the automotive industry.
Automakers are using thinner materials, building lighter and stronger vehicles, and redesigning automobiles with different points of strength for better crash resistance. The driving force in all of these trends is the quest for quality.
"As the world market opens up, more competitors are entering the arena," said Harry deCourcy, Midwest regional sales manager for Cloos Robotic Welding, Schaumburg, Ill. (www.cloos-robot.com). Cloos Robotic Welding produces high-tech, turnkey welding and cutting systems.
"Automakers and their suppliers face competitors whose lower labor costs are reflected in their prices. These new competitors are offering longer warranties to attract customers who may be skeptical of their product."
On the welding side of automaking cost containment, it's important to find the most efficient methods and processes to produce parts, according to Paul Cleveland, OEM and automation support manager for Miller Electric, Appleton, Wis. (www.MillerWelds.com). Miller Electric is a manufacturer of arc welding and cutting equipment.
"[It's important to] offer equipment that is energy-efficient and capable of running processes that contribute to efficiency, equipment that also is flexible in how it can be used," he said.
In addition to power sources as a component of auto manufacturing, the welding wire used also can play a role in efficiency, productivity, and the quality of the end product.
"Historically, automotive components such as frames have been welded with small-diameter, solid mild steel GMAW wires," said Bob Bynum, territory sales manager of ESAB Welding & Cutting Products, Florence, S.C.(www.esab.com), a manufacturer of welding and cutting products. "In recent years welding conditions have been stretched to the maximum. Travel speeds and welding currents have been pushed to their upper limits with today's welding power source technology. Purchase prices of these wires and machines have been driven to their lowest."
For Tier 1 and Tier 2 suppliers to realize improvements in productivity or reductions in the unit cost of deposited weld metal, one of three things must happen, Bynum said.
"First, there has to be further cost reductions of weld wire, which is not likely. Second, welding power source technology must be developed to a higher level in order to get greater performance from the solid GMAW wires in use today, which is also not very likely. Or third, users must seek alternatives to solid GMAW wire," he said.
"The most readily available product that is commercially available today is metal-cored welding wires. They can be run on existing equipment, thereby eliminating the capital cost of new, technologically advanced welding power sources. In most cases, they can be used with existing shielding gas mixtures, provided they are using argon-rich mixtures."
A benefit of using metal-cored wires is that they deposit weld metal at a higher rate than solid wires at the same welding current, allowing for faster travel speeds, which result in shorter weld cycle times, which then reduce the unit cost, Bynum said.
Just as automobiles themselves have changed and continue to evolve, so have the welding processes and equipment used to manufacture them.
"The auto manufacturing cycle has changed in the last 15 years. Concept-to-completion time has gone from nine years to three years or less. People using old technology are behind the times," Occhlialini said. "Before, we used CV, which overwelds, causes excess distortion, burn-through, and spatter and requires expensive gases."
Now faster electronics are available to automakers that are able to take advantage of automated welding, deCourcy said. "Cloos is providing welding wire feed rates of over 1,200 IPM," he said. "It then becomes critical to provide the tracking accuracy and high travel speeds to take advantage of this capability. In addition, power sources that allow weld data monitoring provide a backup and records for quality control."
Lasers also continue to advance in their usefulness for automotive applications.
"The CO22 laser has evolved—and continues to evolve—to a high-performing, minimal-maintenance tool," said Frank Brennan, laser product manager of TRUMPF Laser Technology Center, Plymouth Twp., Mich. (www.us.trumpf.com). The Laser Technology Center is a division of TRUMPF Inc. and supplies industrial lasers and laser application consulting. "Technology has emerged that pushes its performance to a near-solid-state device. As well, the Nd:YAG evolution to diode-pumped technology will greatly enhance the operating efficiency and cost-effectiveness of the product."
As equipment and processes evolve, automakers should expect to see changes in precision and in alternatives to traditional procedures to increase productivity and efficiency, equipmentmakers said.
Examples include more precise process controls and the use of welding processes that allow for more uniform filling of gaps. "There will be a greater emphasis on seeking viable alternatives to traditional procedures," Bynum said, "in order to continue to reduce dependence on labor and increase the speed at which technological advances are not only embraced but actually integrated into manufacturing production."