Selection and evaluation of joint types and joining processes for concurrent assembly/disassembly-based design

In designing products, Design-for-Assembly (DFA) has been successfully used for several decades to reduce lead times, processing times, and equipment overhead. Though the DFA approach results in products which are easy and efficient to assemble, such products may be difficult to disassemble and/or may adversely affect the environment. These environmental concerns resulted in the Design-for-Disassembly (DFD) approach, which stresses ease-of-disassembly and environmental compatibility. However, when applied independently of DFA, DFD underestimates the importance of assembly, and consequently can result in increased assembly time and cost. Design-for-Assembly may thus have negative repercussions on disassembly, and vice-versa. Consequently, in order to minimize assembly/disassembly time and cost and maximize component reusability, designers must implement DFA and DFD simultaneously when designing products. In this research, such an approach is developed. The approach, called Concurrent Assembly/Disassembly-Based Design (CAD²), consists of simultaneously selecting joint types and joining processes for products, based upon both assembly and disassembly requirements. Two objectives are considered: the minimization of total assembly/disassembly time or cost. In addition, a ‘penalty score’ measure is developed to quantify the environmental impact (recyclability) associated with any solution. Total enumeration is used to solve these minimization problems. The CAD² approach is demonstrated and evaluated by comparing it with both DFA and DFD for a limited number of cases. The results indicate that the CAD² approach can give better solutions (total time and total cost) than either DFA or DFD.