The Steel Unibody: The Application of Cost Analysis to Determine Cost Reduction Strategies

Despite repeated challenges from alternative materials and processes, the stamped and spot welded steel unibody remains the near-unanimous choice of automakers for vehicle body-in-white (BIW) structures and exterior panels in volume production. Conventional steel's only weakness is mass; aluminum and polymer composites offer the potential for considerable mass savings, but generally at a higher cost. Efforts within the automakers as well as by outside organizations such as the international steel industry's Ultra Light Steel Auto Body (ULSAB) program are underway to improve the steel uni-body's mass and cost position.

To reduce cost, it is first necessary to identify cost. The measurement of cost for a complex system such as an automobile BIW is far from a trivial task. This paper presents an analytical approach to understanding the manufacturing cost for a conventional steel unibody. The results of this cost analysis are then used to outline a strategy for future cost reduction.