Proceedings of the 2014 Industrial and Systems Engineering Research Conference Y. Guan and H. Liao, eds. A Fuzzy Logic-Based Approach for Handling Uncertain EOL Options in Product Design Stage Junfeng Ma 1 and Gül E. Kremer 2,1 Department of Industrial and Manufacturing Engineering 1 School of Engineering Design 2 The Pennsylvania State University, University Park, PA 16802, USA Abstract Today, companies must consider sustainability in addition to their own primary requirements (e.g., cost saving) and to outside constraints (e.g., environmental protection). End-of-life (EOL) option has emerged as a critical factor in sustainability. However, determining EOL options at the product design stage is complicated. For example, design- stage EOL options for retired bicycle components are various, and change with geographic location. Therefore, fixed EOL options in the design stage may not always be appropriate; thus, uncertain EOL options should be considered. Limited research exists discussing uncertainty in EOL options at the design stage, and this fact motivates this investigation. In our proposed approach, fuzzy logic is employed to handle uncertainty. The probability of each EOL option is determined by aggregating fuzzy set operations and left-right hand fuzzy rank method. An expected value is derived to represent sustainability value of EOL options. Coffee maker is used as a case study to illustrate the methodology. Key Words: End-of-Life, Uncertainty, Fuzzy Logic, Modular Product Design. 1. Introduction Product design is a creative process that harmonizes the needs of customers, the strategy requirements of companies, and the environmental constraints of government regulating agencies. Four stages comprise product design: problem definition, conceptual design, preliminary design and detail design; and all design requirements should be fulfilled through all four stages. Since approximately 70% of product cost [1] and 80% of product quality [2] are determined during the design stage of product planning, product design is a critical concern for developers. Modularity is a methodology used to reduce complexity by breaking a complicated whole into several relatively simple parts. Modular product design (MPD) involves applying the module concept to product design to increase the efficiency and effectiveness of the design process. Many aspects of MPD methods benefit product design, such as easy assembly, low supply chain cost and mass customization. Therefore, applying an MPD method during the design stage has become a trend. Given increasing environmental and social concerns, sustainability management, especially in product life cycle management, has gained a great deal of attention. Product life cycle management involves a product’s entire life and end-of-life (EOL) options. EOL options create lots of energy waste, environment pollution, and cost during the entire product life cycle; accordingly, research efforts have increasingly tended to focus on this area and take product EOL options into account during the design stage. The aggregation of MPD and life cycle management in the design stage is currently popular, and many researchers have developed new product design methodologies. However, both entire life cycle-based and EOL-based methods hold a critical assumption: EOL options have typically been determined before developing methods, which means that EOL options are fixed and treated as constant inputs [e.g., 3, 4, 5, 6, 7, 8, 9]. There is almost no research considering uncertainty in EOL options and MPD simultaneously. Therefore, the purpose of this research is to develop an approach to handle uncertainty in EOL options, and show its implementation within MPD at the design stage.