Interlocking problems in disassembly sequence planning

Remanufacturing is the rebuilding of a product to specifications of the original manufactured product using a combination of directly reused, repaired and new parts. Disassembly, the first and arguably most important process in remanufacturing, tends to be labour-intensive due to complexities in the conditions of end-of-life products returned for remanufacture. Robotic disassembly is an attractive alternative to manual disassembly but robotic systems cannot plan disassembly sequences automatically and manual planning is still necessary. Planning requires machines to interpret physical space using a suitable representation to reflect physical contacts and constraints as well as rules for deciding the sequences of disassembly operations. This paper proposes a representation to describe physical contacts and constraints, and a new approach allowing machines to plan disassembly using the representation. The approach involves employing an assembly matrix and simple logic gates to generate a contact matrix, a space interference matrix and a relation matrix. Rules and algorithms are discussed to explain the calculation of sequences through manipulating the three matrices. A key benefit is that the proposed method can deal with interlocked mechanical structures which cannot be handled using conventional methods. The proposed method is also flexible and is suitable for either selective or complete disassembly.