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The reduction of fuel cell stack cost is a primary objective of the entire fuel cell development community. Among the significant contributors to stack cost in polymer electrolyte membrane (PEM) fuel cells are metallic bipolar plates, which are increasingly viewed as the leading bi-polar plate contender in transportation applications. The U.S. Department of Energy has specifically targeted bi-polar plate cost reduction in its current 100 Mio US-Dollar research initiative. Metallic bi-polar plates are expected to be fabricated in high volume from pairs of thin sheet metal stampings of 100 micrometer to 200 micrometer thickness. The pairs are generally required to be joined or sealed near their perimeters and around apertures through the plates. In addition to these hermetic sealing requirements, there may also be the requirement to produce electrical contact locations throughout the flow field region of the bi-polar plates. Among the many techniques for producing these seals and joints, laser welding has emerged as a likely production solution. Laser lap seam welding for thin, fuel cell, sheet steel components is shown. In such a case the laser beam penetrates through the top sheet and partially or fully through the second sheet. The process is tolerant to lateral alignment but typically considered to be more sensitive to gapping between sheets. The traditional guideline for maximum gap between sheets is 10% of material thickness. This requirement for gap control puts considerable demand on clamping and fixturing of the parts to be welded. For instance a pair of 0.1-mm-thick sheets would normally require a gap of no more than 10 micrometer, a value not easily achieved with production fixturing. Nevertheless, laser lap welding has already been accomplished in R&D quantities of tens or even hundreds of components. In order to accomplish a weld the laser beam must be capable of being focused to an effective diameter that is no more than about half the desired weld width. In the case of a 0.1-mm-thick fuel cell component a desirable weld width would be in the range of 30 micrometer to 60 micrometer, depending on the relative performance requirements of sealing and structural strength. To achieve such a weld width the focal spot of the laser beam would then be required to be between 15 micrometer and 30 micrometer in diameter. Fortunately, the virtually perfect laser beam qualify of newly available fibre lasers makes this range of laser focal spot diameters feasible. The challenge then is to couple such a laser beam with a motion system capable of delivering the speed, accuracy, and dimensions required for fuel cell component assembly.