The cost-saving, weight-reducing, safety-enhancing benefits of tailored blanks have pushed the cutting-edge innovation to become standard. And now, various manufacturing segments are benefiting from this technology.

Rachel Trem, Associate Editor

Welded blanks are indexed out of the LW-B robotic system into post-weld processing.

In 1999, tailor-welded blanks were still an innovation — the cutting edge of automaking. Olympic Laser Processing was a frontrunner with this technology with its facility that laser welds blanks in Van Buren Township, MI. Shortly, steelmakers and processors were linking up to serve the auto industry's growing preference for laser-welded blanks.

Since then, technology and demand have driven these new operations into a distinct industry segment here, in Europe, and in the Pacific Rim. Recently, Japan's JFE Steel purchased a $4.5 million welding line to keep up with the budding segment.

Automakers are using tailor-welded blanks to make cars safer, lighter, and more environmentally efficient; tailored blanks have become the future of automaking.

Tailor-welded blanks are steel sheets of different thickness and grades laser welded into a single flat blank prior to pressing to achieve the optimal material arrangement and weight reduction for cars, and to increase process efficiency and machine flexibility.

Vehicle weight savings, part-count reduction, an improved stiffness/weight ratio, enhanced crash energy management, and an overall reduction in manufacturing costs are the results. With this manufacturing approach, automakers can add strength to parts where it is needed and reduce a vehicle's overall weight and cost.

Bob Lewinski,v.p., marketing and sales for VIL/Wayne Trail Technologies, explained the advantages of tailor-welded blanks. "It may be desirable to form a component such as an inner door panel that has a deep-draw depth to accommodate the contour of the finished vehicle door. This requires a very soft, and relatively thin metal. However, the front of the same inner door where the hinges will attach have to be strong enough to hold up the weight of the entire door. In the past, this would have required the addition of several extra parts to strengthen this area. By producing a tailored blank with a large, thin soft piece of flat material joined to a thick, stronger small piece of flat material, this customized blank can then be formed into one piece inner door, deeply drawn in one area."

He explained that using these blanks produces other tangible savings including reductions in scrap and weight, and improves dimensional accuracy by limiting use of higher-strength, heavier-gauge, more expensive materials.

This is good news for steelmakers concerned about losing market share to plastics and aluminum in auto body construction. The global Ultralight Steel Auto Body (ULSAB) consortium relied on the tailor-welded blanks to keep steel ahead of the pack in automaking.

The Way It's Done
VIL Laser Systems, one supplier and manufacturer of systems and equipment for laser-welded tailored blank production, has been involved with the process since 1989, when GM proposed the idea.

VIL manufactures the LW-B Robotic Tailored Blank Laser Welding System, a fully automated in-line system that processes linear-welded tailored blank sizes and shapes including door inners, hatchbacks, body sides, and floor pans. This flexible system will change from one job to another in less than 30 min., and because it is supplied with a multiple parts processing option, multiple sets of smaller linear-welded blanks can be processed in a single system cycle.

The VIL process starts with two robots that draw blanks from separate stacks and transfer them to an edge-prep station. The blanks are positioned by a sequenced back transfer-belt routine.

Blanks are transferred by the servo-indexing conveyor to the weld station. The transfer and gauge system perform precision part location, high-pressure clamping, and laser welding with a moving overhead laser torch assembly. Weld speed, length, seam position, and all parameters are set prior to operation; laser torch head axes are positioned manually.

The welded blanks are unclamped and automatically indexed out of the weld stations along a magnetic belt conveyor into the stacking station or other optional post-weld processing stations.

When the welded blank is indexed out of the weld station, the next set is simultaneously indexed to the gauging, clamping and welding areas. A third robot services the stacking station and optional inspect/reject station at the end of the line.

Swiss machine builder Soudronic Automotive also offers systems that laser-weld tailored blanks. But, aiming to achieve more than linear welds, which puts certain restraints on the design of the car body, Soudronic has a system for non-linear welds.

The Soutrac laser welding system was developed to produce non-linear and complex linear tailored blanks. It welds various steel grades and material strengths ranging from 0.6 to 3 mm. These are high-quality welds because of a proprietary gap-closing system featuring a camera-monitored, computer-controlled feeding device for the filler wire. Equipped with a quality assurance system, all weld seams are carefully checked for irregularities, like porosity or pinholes. The process joins cold-rolled and galvannealed sheets.

Getting Involved
The manufacturing segment that has emerged thanks to such systems has drawn steelmakers and processors all over the world. Soudronic received an order recently from China's FBS Steel Processing & Distribution, for one of their systems. This order covered a fully automatic tailored-blank line for welding all types of seams, including linear, linear shifted, complex linear, and real curved seams.

JFE Steel supplies automakers with various materials to reduce vehicle weight and improve environmental efficiency; it is active in Early Vendor Involvement programs as a way to increase customer satisfaction. Now, it is adding a tailored blank facility to supply automakers a wider assortment of parts. The line, due to start operating at the Mizushima Works this summer, will be the first tailored blank line in a Japanese steel mill.

JFE's facility will be patterned after one designed by Germany's ThyssenKrupp AG. TK is supplying a $4.5-million Conti Laser Welding Line built by one of its affiliates Nothelfer GmbH. Properties include: weld length of 200-2,200 mm; blank width of 400-3,000 mm; thickness of 0.55-3 mm; and a capacity of 2 million sheets a year. Last April, Pohang Iron & Steel opened a tailored blank production system at its Kwangyang Works in South Korea. But, it is in North America that the tailored blank segment has developed most. Canadian steelmaker Dofasco acquired the Powerlasers operation in Concord, OH; and TWB Co., L.L.C, Monroe, MI, expanded to Mexico in an effort to provide laser-welded blanks to the Mexican automotive market. And, the consolidation of U.S. steelmakers has reshaped the tailored blank segment. Along with its OLP share, U.S. Steel now controls ProCoil thanks to its takeover of National Steel.

AHHS Plus TWB
The advances in tailor blanking have been supported and paralleled by developments in material properties, manufacturing processes, and structural design.

ULSAB-AVC initiated a study that demonstrates how steel can be used in the auto industry. It introduced new steels, advanced manufacturing processes, and innovative design concepts. Incorporating tailored blanks with new grades of advanced high-strength steel (AHSS), automakers can reduce a vehicle's environmental impact, improve fuel efficiency, recyclability, safety performance, and affordability. These designs exhibit a combination of strength, formability, and crash energy management.

According to trade reports, another study by steel industry researchers in the U.S. and Japan assembled tailored blanks made of AHSS using laser welding. An evaluation of the blanks, made of various dual-phase steel grades with tensile strengths up to 1,000 MPa, demonstrated favorable results in weld quality, material formability, and fatigue performance.

Sources said the research showed auto components made of a single type or grade of AHSS can reduce weight and improve crashworthiness according to auto product engineers. When two or more grades are combined in tailored-blank manufacturing process, components made from the blanks provide even greater improvements in those areas while reducing waste and costs.

A Bright Future
The coming years will be anything but blank. As automakers move toward safer, environmentally efficient cars, tailor-welded blanks will play a greater role.

"The future holds steady growth in tailored blank demand and production. And, with this growth, significant quality assurance improvements will surface alongside the increased production capability," Lewinski said.

All manufacturing segments associated with this technology, including steel suppliers, production manufacturers, and automakers will benefit from tailored blanks.

"It is an exciting time in this industry," Lewinski concluded.

Tailored Blanks Drive Design Decisions Automakers, producing everything from wagons to pickups, are making the most of this research. Some automobile platforms already require 20 or more tailored blanks. A number of 2004 models demonstrate the versatility of tailored blanks. Ford's redesigned F-150 pickup uses tailored blanks for its full body side panels, door rings, and B-pillars. Industry reports say Rouge Steel, Inspat Inland Inc., and USS will supply steel for the blanks. The body-side panels have partially exposed sections — a first in the auto industry. Stiffer door sills and openings, together with laser-welded blanks for the body-side panels, provide additional safety. Expecting to build in volumes of 750,000 to 1 million units per year, Ford's use of the blanks in the popular pickup is seen as the biggest application. Reportedly, Ford chose tailored blanks in the new F-150s because the reduce component weight and material waste. Their future designs (including cars, minivans, and SUVs) will extend Ford's use of tailored blanks. Chrysler and General Motors are also on the tailored-blank bandwagon. Industry reports recognize Chrysler as having the highest percentage of tailored steel in its vehicles. The Chrysler Pacifica uses eight tailored blanks for major body parts, including large body-side inners, door inners, and lift gate inners. Using AHHS steels, including tailored blanks, is approaching 50% in vehicles of this type. GM's Chevy Malibu uses tailored blanks on the body side-inner panels, as well as all four side-door inners, a pair of engine compartment rails, the upper-rear side rails, and on some, the extended wheelbase. Using different AHSS applications and tailored blanks, a stiff body structure, and efficient mass with quality, safety, ride, and handling is achieved. Overall part totals and weld counts are reduced, and dimensional control is increased. Laserwelded blanks for the front and rear rails reduce the mass by about 5.5 lbs. AK Steel is one of the mills furnishing the steel for the tailored blanks. Laser Welding International Inc., Clinton Township, MI, Shiloh Industries, Cleveland, and ProCoil Corp., Canton, MI, will make the blanks.