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Lasers, Welding, Automotive industry
Abstract
Describes the development of laser welded tailored blanks and the benefits they bring to car design. One of the principle advantages is weight reduction, which steel makers have seized on to counteract the "threat" from aluminium and have invested in a number of laser welding facilities. One of these lines, at Laser Welded Blanks (LWB) in the UK West Midlands and supplied by VIL, is described in detail. The system features the VIL-developed and patented edge preparation station (EPS) that incorporates a precision shear. In this way, the mating edges of the pieces are prepared with the close fit-up needed to produce high quality blanks and allow welding at high speed. The VIL system, which is limited to linear welds, is contrasted with the more complex non-linear system developed by some manufacturers.
The monocoque construction of a modern car body is made up almost entirely of steel pressings, ranging in size from a complete body side to the smallest of support brackets. In the main each pressing is produced from a single gauge sheet blank that is formed into its final shape before various bracketry and other components are added to produce the finished sub-assembly. However, in the last two or three years the concept of tailored blanks has emerged in which two or more sheet pieces differing in shape, gauge and even material specification, are welded together so that the ensuing sub-assembly is lighter, has fewer components, is stronger and costs less. It is transforming car body assembly, and every new car introduced now includes an increasing number of pressings produced from tailor-welded blanks (TWBs).
The development of TWBs appears to have occurred more or less simultaneously during the 1980s in Europe, Japan and the USA. However, speaking at a workshop organised by the British Association of Industrial Laser Users (AILU), Masakazu Tsuji of the Hanwa Company, stated that as early as 1967 Honda had produced a tailored blank for a body side ring. This was a highly ambitious development using five separate pieces in three different gauges, which even today is considered to be a complex product.
The basic problem with the Honda TWB was the TIG welding of the pieces. This caused...