Journal of Engineering Design Vol. 18, No. 6, December 2007, 563–575 Design for disassembly: a methodology for identifying the optimal disassembly sequence FEDERICO CAPPELLI*, MASSIMO DELOGU, MARCO PIERINI and FRANCESCO SCHIAVONE Università di Firenze, Italy Optimizing the disassembly sequence of mechanical systems is very useful in order to improve maintenance and recycling activities (i.e. to reduce costs, times and number of operations). A new virtual disassembly environment, based on two different algorithms, is presented. The first analyses the physical constraints that oppose the movement of the mechanical element: starting from its three- dimensional computer-aided design representation, it creates the ‘AND/OR’ graph of a mechanical assembly that represents the space of disassembly solutions. The second algorithm, using a represen- tation based upon binary trees, allows the automatic exploration of the set of all possible sequences. Among these, the optimal one can be identified, choosing a specific target function. The developed methodology provides the theoretical basis for the creation of a computer-aided design tool able to evaluate the ability to disassemble a mechanical complex during the early design phase. Keywords: Design methodologies; Product design; Design for disassembly 1. Introduction The problem of the environmental impact of new products and production processes led to the development of new methods for the evaluation of polluting emissions from the early stage of the design. Such a methodological approach is called EcoDesign (Holt 1992, 1994): it repre- sents a multi-objective design process that realizes the best compromise among environmental, technical and economical specifications of a product. The ‘Design for Disassembly’ (DfD) is one of the EcoDesign methodologies: it intends to optimize the disassembly operations to which the product will be exposed during its lifetime, in order to reduce maintenance costs (Tsai et al. 2003) or to allow cost-effective reuse, reman- ufacturing and recycling. The useful life of a product is extended through the maintenance programme, while the reuse and the remanufacture operations can extend the useful life of some parts. Recycling decreases the need to extract and process virgin raw materials that are used in manufacturing processes for the new projects: thus, the disassembly is not a set of random actions of decomposing a product, systematically mounted, but it is driven by the objectives to be reached. *Corresponding author. Email: federico.cappelli@unifi.it Journal of Engineering Design ISSN 0954-4828 print/ISSN 1466-1837 online © 2007 Taylor & Francis http://www.tandf.co.uk/journals DOI: 10.1080/09544820601013019