Profit-oriented disassembly-line balancing

As product and material recovery has gained importance, disassembly volumes have increased, justifying construction of disassembly lines similar to assembly lines. Recent research on disassembly lines has focused on complete disassembly. Unlike assembly, the current industry practice involves partial disassembly with profit-maximization or cost-minimization objectives. Another difference between assembly and disassembly is that disassembly involves additional precedence relations among tasks due to processing alternatives or physical restrictions. In this study, we define and solve the profit-oriented partial disassembly-line balancing problem. We first characterize different types of precedence relations in disassembly and propose a new representation scheme that encompasses all these types. We then develop the first mixed integer programming formulation for the partial disassembly-line balancing problem, which simultaneously determines (1) the parts whose demand is to be fulfilled to generate revenue, (2) the tasks that will release the selected parts under task and station costs, (3) the number of stations that will be opened, (4) the cycle time, and (5) the balance of the disassembly line, i.e. the feasible assignment of selected tasks to stations such that various types of precedence relations are satisfied. We propose a lower and upper-bounding scheme based on linear programming relaxation of the formulation. Computational results show that our approach provides near optimal solutions for small problems and is capable of solving larger problems with up to 320 disassembly tasks in reasonable time

Determining optimum disassembly sequences in electronic equipment

This paper presents a study on disassembly sequence generation for electronic equipment. This is particularly useful because adequate end-of-life disassembly becomes crucial as take-back obligations are imposed for environmental reasons. Besides this, the hierarchical structure, typical to electronic products, makes product remanufacturing to an important topic. Methods from disassembly of mechanical assemblies are successfully adapted to these specific challenges. First, a modeling method for assemblies is described, which is aimed at automatically determining the optimum disassembly sequence. It is argued that the information, which is condensed in the connection diagram and the set of precedence relations, is sufficient for the automatic generation of such a sequence. Appropriate use of the precedence relations reduces the size of the model, that can be represented as an AND/OR graph with a restricted number of subassemblies and actions. With disassembly costs and revenues included, the optimum disassembly sequence can be found with standard linear programming software, thus without the need of visiting the complete search space. As a matter of fact, the size of the problem is strongly reduced, as it increases only linear with the number of parts in the assembly. It has been demonstrated that the model nearly instantaneously generates the optimum disassembly sequence. Besides this, the model can generate near optimum sequences as well, which is beneficial if multiple criteria are considered

Hergebruik en recycling van complexe producten

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