Measuring Product Design Sustainability Based On Design for Assembly and Design for Disassembly Using Life Cycle Assessment

Sustainable manufacturing has become imperative all over the world in the current century. Manufacturers are trying to understand the need for the responsible use and management of resources in the life cycle of a manufactured product, especially the planning for product retirement. In order to measure the design sustainability of a product, cost analysis based on design for assembly and design for disassembly cost and end of life value is used. Design for assembly is an approach to design the product in the way that has least number of parts and simplest assembly process with minimum cost required. This design for X approach has many guidelines developed mainly by quantitative evaluation method such as Boothroyd-Dewhurst Design for Assembly Method, Hitachi Assemblability Evaluation Method and Lucas Design for Assembly Methodology. In case of guidelines, reducing part count and part types, striving to eliminate adjustments, Designing parts to be self-aligning and self-locating, Ensuring adequate access and unrestricted vision, Ensuring the ease of handling of parts from bulk, Minimizing the need for reorientation during assembly, Designing parts that cannot be installed incorrectly, Maximizing part symmetry if possible or make parts obviously asymmetrical are considerable. Each of this considerations in will make different costs in each part design for assembly. On the other hand design for disassembly is an approach to find the best disassembly sequence with least time. This also consists of some guidelines like combining elements, Limiting material variability, using compatible material, Grouping harmful materials to subassemblies, Providing easy access to harmful, valuable or reusable parts, using Accessible drainage points, Using fasteners easy remove or destroy, Minimizing number of fasteners. Applying these guidelines result in different disassembly costs. In fact design for assembly severely influence design for disassembly cost which should be considered in life cycle assessment. Each option for end of life value has a cost that should justify disassembly cost; else the product will not be considered as a sustainable product. In these paper four case studies including an electric pot, a hair clipper, a speaker and a printer are analyzed based on assembly, disassembly and end of life option. If end of life option justifies the disassembly cost of a part, that part is considered a sustainable part, but steel the product may be unsustainable. If total cost analysis of parts in a product can justify product disassembly or product recycling it is considered a sustainable design. Based on the justified percent of disassembly cost by end of life value a sustainability design measurement is assigned to each product.