An integrated model and its extension for disassembly leveling and lot-sizing for multiple product types

Disassembly leveling, one of disassembly process planning decisions, is to determine disassembly structures that specify parts/subassemblies to be obtained from used/end-of-life products, and disassembly lot-sizing is the problem of determining the amounts of disassembly operations required to satisfy the demands of their parts and/or subassemblies. In this study, we consider the two problems at the same time for the objective of minimizing the sum of disassembly setup and operation costs. In particular, we consider a generalized version in which disassembly levels may be different even for products of the same type. Two types of the problem are considered: (a) basic problem without parts commonality, i.e., products do not share their parts/subassemblies; and (b) extended problem with parts commonality. For the basic problem, a polynomial-time optimal algorithm is suggested after developing a mathematical programming model. Also, we show that the extended problem is NP-hard and then suggest a heuristic, together with its computational results.