Tailored blanks come on strong

Automotive Manufacturing & Production, May, 1997 by Al Wrigley

Other benefits have been noted - including reductions in stamping die and spot welding requirements - but the weight savings factor has proven to be particularly important to auto product engineers. Because the auto industry's experience with tailored blanks has involved steel, primarily, as the blank material, tailored blanks also are now helping the steel industry maintain its dominance in auto body and structural components applications.

In fact, both the domestic and world steel industries regard the role played by the tailored blank-manufacturing technology to be critical to their efforts to make steel more presentable to the auto industry than it has ever been before as the principal material in cars and light-duty trucks. This technology has played - and continues to play - a critical role in such projects as the "Light Truck Structure" (LTS} and the "UltraLight Steel Auto Body" (ULSAB) being conducted by those industries. Both projects are aimed primarily at showing the automakers how steel can be used in their vehicles in the future at reductions in weight and cost, without sacrificing quality and performance. (See "Creating a Better Truck" in this issue.)

Also known as "engineered blanks," tailor welded steel forms are now being made by numerous companies around the world, including some of the automakers themselves. Although regarded by some automen as still being in its infancy, the technology has grown enough to be playing a role in just about every new or redesigned car and light truck introduced each year in the U.S.

The list of applications introduced in the 1997 models, for example, included the inner front door panels on General Motors' front-wheel-drive minivans; the C-pillar inner panels and liftgate header outer panels on Ford Motors Co.'s new Expedition sports utility vehicles; and the front fender inner panels and inner door panels, as well, on Chrysler Corp.'s Dodge Dakota pickups. All of the blanks from which these components are stamped are steel, and the rest of the lengthy list of 1997 U.S. applications also involves steel, almost exclusively.

In the 1997 calendar year, engineered blank manufacturers in the U.S. and Canada are handling more than 42 - and possibly as many as 52 - different orders, or jobs, for the automakers. Next year's total is expected to be in the area of 60 or so. Because these blanks are the feedstock materials for the automakers' stamping presses (or, in some cases, their parts suppliers' stamping presses), both the blanks and the stampings involved in many of the jobs are produced in high volumes.

In Europe, where the production of tailored blanks began in the early '80s, steel parts made from such blanks are thought to account for 3-5% of the average new car's body weight. Total estimated production of engineered steel blanks in Europe this year will be 265,000 tons or more.

Both production and use of these blanks in North America trail Europe's, but year-to-year growth in the number of applications is thought to be as high on a percentage basis in North America as it is in Europe - if not a little higher. The most common method for assembling such blanks in North America is laser welding, whereas the most common in Europe is resistance mash seam welding. Laser welding is second in Europe, where high-frequency induction welding and non-vacuum electron beam welding also are being tried.

Laser welding in the tailored blank-making business is a full-depth fusion (butt) welding process that produces very narrow, hard welds. Mash seam welding is a roller-using resistance welding process that requires a small overlap of the small strips or sheets that are being joined to form the larger engineered blanks. A mash seam weld is thicker than, but not as hard as, a laser weld in tailored blanks. The mash seam weld also tends to be wider than the laser weld. The overlap at the joint of a mesh seam weld is generally reduced by a post-assembly planishing process.

In North America, the first two companies to get seriously involved in the tailored blank-making business a few years ago were the Utilase Blank Welding Technologies division of DCT Inc., Detroit, and Medina Blanking Inc., a unit including TWB Co., a joint venture between Thyssen Steel-North America and Worthington Steel Co., Monroe, MI; Triam Automotive Inc., Toronto, Ontario; and Laserweld International, a subsidiary of Lobdell Emery-BMG, North Vernon, IN. Toyota Motor Mfg. USA Inc., Georgetown, KY, also produces such blanks.

One of the reasons the technology is still considered to be in its infancy is the presence of only a few manufacturers and the difficulties of "earning a living" in the field, which is often experienced by companies engaged in a new kind of business with new and complex equipment.

The list of applications for such blanks is expanding, however, and there is little doubt that the business will continue to grow and leave its mark on the world of automotive manufacturing.

Many product engineers, buyers, and manufacturing engineers in the auto industry are supportive of the technology, which they see as an opportunity to reduce materials and manufacturing costs while also reducing component weight. Domestic production applications for tailored blanks, in addition to those mentioned above, include floor pans, door rings, frame rails, windshield frames, bumper reinforcements, and numerous other components.