Integration of Functional and Environmental Performance Design Decisions: A Mechanical Component Case Study

Product design-for-environment (DfE) has traditionally relied on life-cycle assessment (LCA) as a primary means of assessing environmental performance. To date, LCA has focused on static inventory and impacts of material streams during the stages of resource extraction, component manufacture, product use, and end of life at a high level of aggregation. Improvement analysis, though theoretically an important stage of LCA, is practically very challenging to implement using LCA alone. One reason for this is that the focus on detailed characterization of material streams does not facilitate a development of an understanding of the mechanistic relationship between design intent and material, manufacturing, and use-phase potential impacts. As the product development community transitions from sequential design to more streamlined concurrent design, interactive design tools are needed as a supplement to assessment tools in order to facilitate tradeoffs among environmental and other factors. This article presents an environmental analysis approach based on detailed process modeling which evaluates components from a functional design point of view. From a manufacturer's perspective, local potential effects in aggregate are often as important as global potential impacts. Furthermore, impacts often relate to explicit trade-offs between different life-cycle stages, such as production and use. In this article, the influence of functional design and manufacturing specifications (surface tolerance and finish) on localized potential impacts is illustrated through two different mechanical component (steel roller bearing and rotating shaft) case studies. Detailed analytical tools are key in enabling optimization and trade-offs by designers and process planners. The functional modeling approach is an important complement to LCA in providing a well-defined view of environmental performance.