INDUSTRIAL LASERS

Automakers face a common problem--how to reduce a vehicle`s weight to improve its operating efficiency. In the USA, it is called combined average fleet efficiency; that is, by certain dates, the average fuel economy, as mandated by the federal government, must meet specific miles/gallon criteria for an entire auto manufacturer`s fleet.

INDUSTRIAL LASERS

Tailored blank welding improves auto efficiency

Automakers face a common problem--how to reduce a vehicle`s weight to improve its operating efficiency. In the USA, it is called combined average fleet efficiency; that is, by certain dates, the average fuel economy, as mandated by the federal government, must meet specific miles/gallon criteria for an entire auto manufacturer`s fleet.

So the drive is on to improve individual vehicle performance, and one way to achieve that is to reduce an auto`s curb weight. Auto-industry designers and engineers are seeking every means available to reduce weight, but they are fighting the rule of diminishing returns, as they have expanded the use of plastic, nonferrous metals, and lighter-weight steels to a point where the rigidity and strength of the auto body are being challenged.

Body parts of different design are now the focus of attention, especially since the rapid acceptance of a process called tailored blank welding (TBW; see cover and photo). In this process, steels of dissimilar composition, thickness, or both are fusion-welded to produce a lighter part with the required strength, stiffness, and formability for subsequent stamping or dee¥drawing. In many cases, the new part replaces one with multiple components or is one that allows designers to achieve previously impossible contours to improve the body design.

High-power lasers play a key role in the meteoric rise of demand for TBW parts. And US auto manufacturers and their suppliers have taken a world leadershi¥position in applying laser TBW to meet the needs of today`s autos and future designs. Carbon dioxide (CO2) lasers with output power to 8 kW, and, recently, CW Nd:YAG lasers at 4 kW, are integrated with beam- and workpiece-motion systems to join various auto-body steel combinations for major structural features such as door inners and outers, bodyside rings, motor rails, A and B pillars, and windshield frames.

In the USA, more than 11 million laser-welded parts will be fabricated this year by major auto-industry subcontractors. Industry experts estimate that this number could easily double in the next three years, as automakers increase the number of TBW parts used. With increased usage in Europe, where a recent shift from conventional mash seam welding has begun, and in Japan, where Toyota pioneered with laser-welding the Camry bodyside ring, future application growth also seems assured well into the next decade.

The growth in this one application is responsible for commercialization of 8-kW CO2 lasers and 4-kW Nd:YAG lasers, each offering certain advantages in TBW. A summary of these appears in a report published in the June 1997 issue of Industrial Laser Review.

David A. Belforte

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