Abstract
This paper addresses a design problem of disassembly and sorting systems in which collected products are disassembled into parts and the parts are sorted into several groups according to the usage method. The disassembly operations are allocated to workstations and the necessary tools are arranged at the workstation. One of the important operations after disassembly is to sort the obtained parts. In general, products consist of many kinds of parts, and the sorting operations are troublesome tasks for the workers. Several boxes are arranged at each workstation and the parts are sorted into the boxes by the workers. The decision variables in the design of the system are the number of stages, the number of workstations in each stage, the allocation of disassembly and sorting operations to the workstations, and the arrangement of disassembly tools and sorting boxes at each workstation. The design problem is formulated as an integer programming problem under a cost-minimization criterion. The problem is solved using the CPLEX optimization software. Numerical experiments are implemented for two types of precedence relationships (the complete serial type and complete parallel type), and the characteristics of the optimal disassembly and sorting system are shown for the precedence relationships. Further, optimal solutions are calculated for the data for cellular phones and personal computers, and it is shown that multistage parallel-station systems are superior to both multistage non-parallel systems and single-stage parallel systems.
