An approach for estimating the end-of-life product disassembly effort and cost

Disassembly is the process of physically separating a product into its parts or subassembly pieces. The overall economics of the disassembly process, and in particular the cost to disassemble, is still not well understood. In this paper our goal is to introduce a methodology that will support and facilitate the economic analysis of the disassembly activity. We present a multi-factor model to compute the disassembly effort index (DEI) score, which is representative of the total operating cost to disassemble a product. The DEI score can then be compared against the projected market value of the disassembled parts and subassemblies to get an economic measure. To develop the DEI model we surveyed a variety of commercial disassembly facilities. Based on these surveys we propose a multifactor weighted estimation scheme. The seven factors are (i) time, (ii) tools, (iii) fixture, (iv) access, (v) instruct, (vi) hazard, and (vii) force requirements. The DEI scale is defined in the 0 to 100 range. This range is assigned on a weighted basis to each of the seven factors. For each factor, an independent utility scale is formulated, using the assigned range as anchors. Using a conversion scale the DEI score is used to derive an estimate of disassembly cost and the disassembly return on investment. An example is presented.     

Evaluation model and algorithm of product disassembly process with stochastic feature

Disassembly planning is considered as the optimization of disassembly sequences with the target of the shortest disassembly time, the lowest disassembly cost, and the minimum disassembly energy consumption. However, obsolete products suffer from the influence of a variety of uncertainties, the disassembly process of products has the strong uncertain feature. Traditionally, to account for this uncertainty, each removal operation or removal task is assumed to be an activity or event with certain probability, and the determination of the optimal path of a disassembly process is merely a probabilistic planning problem based on this assumption. In this article, based on the established stochastic disassembly network graph, combined with different disassembly decision-making criterion, typical stochastic models for disassembly time analysis are developed. In addition, a two-phase approach is proposed to solve the typical stochastic models. Initially, according to different removal probability density functions, disassembly probability density functions of feasible disassembly paths are determined by a time-domain method or frequency-domain method, and additionally, after the disassembly probability density functions have been obtained, the quantitative evaluation of a product disassembly process and stochastic optimization of feasible disassembly paths are realized by a numerical solution method. Finally, a numerical example is illustrated to test the proposed concepts and the effectiveness of the proposed approach.     

Economical evaluation of disassembly operations for recycling,remanufacturing and reuse

This paper introduced a procedure which integrates economical factors into the scheduling of disassembly operations for Material Recovery Opportunities (MRO). MRO are defined as opportunities to reclaim post-consumer products for recycling, remanufacturing and reuse. Traditionally, recyclers have resorted to using heuristics for analysing the breakdown of products and the associated costs. In this paper, a quantitative method of disassembly analysis is developed. Its aim is to improve the efficiency of the disassembly planning process and to generate an optimal disassembly sequence which maximizes profit. Three economic indices are used to evaluate the trade-off between reclamation and disposal of individual components. A systematic procedure of generating an optimal disassembly sequence based on maximizing the profits of material recovery is presented. Three criteria are established to reduce the search space and facilitate recovery opportunities: (1) material compatibility, (2) clustering for disposal, and (3) concurrent disassembly operations. An example is provided on a product being disassembled for recycling at a local recycling plant in Canada.     

拆卸与或图生成及其权重不定问题研究

为了高效地规划装配体的拆卸序列,首先利用生成完备可行子装配体的算法构造所有可行的拆卸操作,并以与或图的形式将所有可行的拆卸操作加以表达,对该与或图进行简约,从而构建能够表达所有可行拆卸序列的拆卸与或图;为了基于该拆卸与或图规划拆卸序列,利用广义权重解决了拆卸与或图中有向边上权重不确定的问题,并给出了广义权重的计算方法;最后,通过实例验证了这种拆卸与或图表达拆卸序列的高效性和用于拆卸序列规划的可行性和有效性.结果表明拆卸与或图是一种可用于拆卸序列规划的高效模型.     

Cyclic lot scheduling with sequence-dependent set-ups: a heuristic for disassembly processes

The importance of material and product recovery is steadily increasing, mainly due to customer expectations and take-back obligations. Disassembly is a major operation in material and product recovery, since returned products are often disassembled to separate materials and components. The paper considers the problem of scheduling several items on a single disassembly facility. It develops a cyclic lot-scheduling heuristic for disassembly processes with sequence- dependent set-ups, resulting in disassembly frequencies for the items. Additionally, the way the problem is formulated allows calculation of the profitable use of the facility. The disassembly frequencies and the profitable use of the facility are used to create a cyclic schedule.     

在Pro/E中自动生成零件拆卸优先约束矩阵

拆卸优先约束矩阵为建立产品的拆卸层次信息图模型提供了基础信息,保证了拆卸序列规划结果的正确性和有效性.在Pro/E中用C语言完成了零件拆卸优先约束矩阵自动生成的二次开发,包括模型调入和预处理、简单拆卸路径生成和包容盒逐级分解的干涉检验等3个模块.解决了自动判别节点可拆卸性的关键问题,为机电产品基于拆卸层次信息图建模的自动化提供了有力的支持.     

工程液压油缸的拆解能量分析

拆解能量是产品可拆卸性评价的关键指标,对产品的可拆卸性设计和再制造回收决策具有重要意义.基于图论思想,构建油缸的拆解约束图并生成油缸的拆卸序列;定义零部件拆解能量的组成模型和传送带移出零部件的能量消耗模型;讨论油缸零部件间典型连接方式与约束解除所消耗能量的数学关系.以某型号工程液压油缸为例,对其零部件的不同拆卸序列进行总的拆解能量分析计算与评估,为油缸的拆卸序列规划、专用拆卸设备设计和液压油缸的可拆卸性设计提供参考.     

Partial disassembly sequencing considering acquired end-of-life product age distributions

Uncertainty management is a priority in remanufacturing operations due to uncertain end-of-life (EoL) product quality, quantity and return timing. Ignoring EoL product uncertainty can result in inefficient remanufacturing operations. In this work, an approach is developed that addresses the impact of EoL product quality uncertainty on partial disassembly sequences. Disassembly is performed on nearly all EoL products, yet it is vulnerable to uncertain EoL product quality, defined in this work as the remaining value of an EoL product compared to original equipment manufacturer standards. The developed approach converges to an optimal or near-optimal partial disassembly sequence provided that information regarding acquired EoL product age distributions is known and correlates to EoL product quality. A mathematical framework is introduced to evaluate disassembly sequences based on profit standard deviation and profit probability as well as the traditionally used expected profit. The approach is tested on an example case study to investigate the impact of uncertain quality on the optimal or near-optimal disassembly sequence, expected profit, profit standard deviation and profit probability.     

拆卸序列规划中子装配体的识别与生成

子装配体识别是解决大规模拆卸序列规划"组合爆炸"问题的有效方法之一.为了准确有效地识别与生成子装配体,在装配体零部件间接触关系、联接关系和向位妨碍关系及其相应图模型、矩阵的基础上,提出了一种基于图模型和判断矩阵的拆卸序列规划子装配体的识别算法.该算法利用图模型对子装配体集合做加法,利用判断矩阵对子装配体集合做减法,首先依据子装配体识别准则对图模型检索生成潜在子装配体集合,然后依据矩阵判断公式从集合中排除不符合连续性原则、稳定性原则和可行性原则的子装配体,并筛选理想个数的符合重量标准、同质标准和价值标准的最终子装配体集合.以减速器实例验证方法的可行性和有效性.     

An efficient GRASP algorithm for disassembly sequence planning

One of the steps in a reverse supply chain is to disassemble the recovered products. The design of such disassembly operations is more complex than that of classical assembly lines. A new GRASP algorithm is presented in this paper for solving Disassembly Sequence Planning, i.e. the determination of the sequence for disassembling component parts. The problem has a combinatorial structure and a large number of constraints. Moreover, checking the feasibility of each solution element is time consuming. The proposed approach is successfully tested against previous best known solutions for a set of public benchmark problems.     

Sustainability through disassembly modeling, planning, and leveling: a case study

The increasing environmental and economic pressures have contributed to the practice of recycling and remanufacturing. Product disassembly is a vital strategy of industrial recycling and remanufacturing which retrieves the desired parts and/or subassemblies by separating a product into its constituents. In this context, decision for disassembly gains importance. Disassembly modeling and planning is a critical activity rather than assembly, because the terminal goal is not vitally fixed, but depends on the product usage and market demands for used parts and recycled materials. Disassembly involves more uncertainties in system structures and components rather than in assembly. This article applies the recent methods for modeling and process planning the disassembly to an industrial product, i.e., rotary switch. The disassembly approach has been practically validated in industrial scenario.     

Disassembly line balancing using linear physical programming

Disassembly is the separation of a product into its constituent parts in a systematic way. It has gained importance recently due to its vital importance in product recovery. Cost-effective implementation of disassembly operation has a direct impact on the profitability of product recovery activities (recycling, remanufacturing etc.). Although it is possible to carry out disassembly operations in a disassembly station or in a disassembly cell, the highest productivity is achieved in a disassembly line. The output of a disassembly line can be maximised only if the line is balanced. A linear physical programming-based disassembly line balancing method is proposed in this study. This method was used to balance a mixed-model disassembly line and the effectiveness of the method was illustrated by analysing the results.     

An improved gravitational search algorithm for profit-oriented partial disassembly line balancing problem

Disassembly is indispensable to recycle and remanufacture end-of-life products, and a disassembly line-balancing problem (DLBP) is studied frequently. Recent research on disassembly lines has focused on a complete disassembly for optimising the balancing ability of lines. However, a partial disassembly process is widely applied in the current industry practice, which aims at reusing valuable components and maximising the profit (or minimising the cost). In this paper, we consider a profit-oriented partial disassembly line-balancing problem (PPDLBP), and a mathematical model of this problem is established, which is to achieve the maximisation of profit for dismantling a product in DLBP. The PPDLBP is NP-complete since DLBP is proven to be a NP-complete problem, which is usually handled by a metaheuristics. Therefore, a novel efficient approach based on gravitational search algorithm (GSA) is proposed to solve the PPDLBP. GSA is an optimisation technique that is inspired by the Newtonian gravity and the laws of motion. Also, two different scale cases are used to test on the proposed algorithm, and some comparisons with the CPLEX method, particle swarm optimisation, differential evolution and artificial bee colony algorithms are presented to demonstrate the excellence of the proposed approach.     

Disassembly sequencing: A survey

This paper is a survey of the presently available literature on disassembly sequencing, including the papers that are closely related to this topic. Disassembly theory is applied to complex products such as mechanical, electromechanical and electronic appliances. It is required for end-of-life processing and for maintenance and repair. Apart from these applications, disassembly is studied for supporting the analysis of assembly processes. Disassembly sequencing involves the search for all possible disassembly sequences and the selection of the optimum solution out of these. In each application, a slightly different approach can be observed, including level of detail, degrees of freedom, and the role of uncertainty. Disassembly sequencing also plays a major role in the modern design process and is an invaluable tool in concurrent engineering. Its connection with the more detailed or component level and the less detailed level or process level including logistics, is highlighted. This presentation of the state of the art is intended as a stimulus for further research in this interesting field.     

基于模块化设计的混合图拆卸建模研究

拆卸建模是拆卸序列规划的基础,也是绿色设计的关键。在传统的拆卸序列规划过程中,随着产品零件数目的增加会造成“组合爆炸”问题。为解决该问题,提出了一种基于模块化设计思想的拆卸建模方法。首先,运用图论中有向图和无向图的概念分别表示零、部件之间的约束关系,并将有向图和无向图结合成混合图,建立产品混合图拆卸模型;其次,利用模块化设计中的模块划分原则生成子装配体,通过将模块化设计方法整合入混合图模型中,得到模块化设计的混合图拆卸模型,利用该模型可以有效地解决图论模型中边与顶点产生“组合爆炸”的问题;最后,以模块化设计的计算机主机箱的混合图拆卸建模为例来验证所提出的方法。     

Optimal disassembly of complex products

This paper presents a method for determining the optimum disassembly sequence for selective disassembly of discarded complex products. This methodology has been developed within the framework of the increasing need for formulation of a theory on selective disassembly and the various purposes of it. The objective of the optimization is maximizing the economic performance of the disassembly process within given technical and environmental constraints. It is demonstrated that the method, that is based on graphs, can be used to generate optimum sequences according to various objectives in a straightforward way. Also a ranking of the most favourable alternative sequence is possible. This is important to the inclusion of other criteria in the model and in adaptation of the disassembly system to fluctuating parameters like material yields and constraints. Contrary to earlier work on generation of disassembly sequences, in selective disassembly all possible incomplete disassembly sequences are included. This considerably increases the number of disassembly sequences to be studied with respect to the number of possible assembly sequences. According to the method described here, the number of viable sequences is determined in a straightforward way. On the basis of a specific example the general methodology is discussed.     

An optimisation support for the design of hybrid production lines including assembly and disassembly tasks

The optimisation problems related to the assignment of tasks to workstations in assembly and disassembly lines have been largely discussed in the literature. They are known, respectively, as Assembly Line Balancing and Disassembly Line Balancing Problems. In this study, both types of task performed on the identical product are integrated in a common hybrid production system. Therefore, the logistic process is simplified and disassembly tasks can supply easier the assembly tasks with the required components. The considered production system has the layout of two parallel lines with common workstations. The product flow is conventional in the assembly line and reverse in the disassembly line. The paper provides a new mathematical model for designing such a hybrid system and an approximate approach based on ant colony optimisation for solving large-scale instances. The solution method is tested in a case study. The obtained results are compared with the solution provided by the design of two independent lines. The analysis of the results highlights the potential benefits of the hybrid production system.     

Development of an automated process planning and production activity control system for the manufacturing of engineered work surfaces

This paper describes the design and implementation of an Automated Process Planning and Production Activity Control system for a make-to-order business and presents a formal methodology for the development of integrated manufacturing systems. The research is based on concepts developed in a project undertaken in a job shop Case Study facility, producing precision-engineered work surfaces. Industry today is facing numerous challenges on many fronts demanding improved availability and dissemination of processing information. On the demand side there is increased pressure on the manufacturer to meet deadlines and provide the customer with a prompt, efficient service, with accurate lead-time information, and a product of the utmost quality, on time. On the supply side there is increasing competition, variety in the market, a diverse product range, varying processing times and extremely short lead times. The nature of today's business world means that real-time information is a requirement and not an extra. This paper documents the design, structure and implementation of an Automated Process Planning system, which completely automates and integrates Order Entry stages from order receipt to order release. The developed system, namely the Manufacturing Optimization Information System, or MOIS, relays information to and from shop floor operators via a Production Activity Control system at each of the manufacturing stations. The MOIS is part of ongoing research endeavouring to integrate order processing, Process Planning and production control activities with a combined dynamic scheduling and material optimization module in a holistic manufacturing optimization system. The two specific aims of this paper are very clear; first, to bridge the theory-practice gap between theoretical concepts and real industrial issues surrounding Process Planning and Production Control. Secondly, to outline the design, structure and evolution of an integrated Automatic Process Planning and Production Activity Control system, installed in a make-to-order enterprise.     

An algorithm for optimising the servicing of products with constrained,multiple defects

The twin pillars of sustainable development are the conservation of natural resources and the management of waste. Waste is generated whenever a product is serviced or repaired, or when it is ultimately discarded at the end of its useful life. In order to manage such waste, the servicing options and costs must first be ascertained. This paper presents an algorithm for the generation of optimal disassembly and re-assembly sequences for the servicing of products with multiple defects, subject to constraints such as inaccessible components. The multiple service action (MSA) algorithm determines the minimum total servicing cost for a product network based on Floyd's Algorithm, a shortest path algorithm. Well-established shortest path algorithms, which compute the shortest route between any pair of nodes in a network, are unable to handle multiple defects. The product network is first constructed, depicting the components and subassemblies as nodes, and embodying in directed arcs, the labour, materials and tooling costs associated with disassembly and re-assembly, as well as the cost to repair, reuse, recycle or dispose the defective components. The MSA algorithm was tested on seven different product networks representing multiple defective components that can be serviced by different feasible routes. For each feasible service route, associated costs were computed. It was established that the algorithm was able to generate optimum disassembly and re-assembly routes for the servicing of products with multiple defects subject to constraints.     

Modelling and planning of the disassembly processes using an enhanced expert Petri net

A sound disassembly Petri net model for the effective planning of disassembly processes and tasks is outlined. Owing to the unmanageable complexity associated with modelling of the disassembly processes and tasks, it becomes essential to have a more powerful Petri net model developed by incorporating the concepts of expert system, knowledge representation techniques, etc. Disassembly task planning at high and low levels can easily be represented by proposed high- and low-level expert Petri net. An algorithmic approach is also suggested for evaluating the end-of-life values of a product. These values are used to determine an optimal disassembly sequence and it is incorporated in the expert disassembly Petri net. A proposed expert enhanced high-level coloured disassembly Petri net is empowered to express such details vividly. The application of the proposed expert enhanced high-level coloured disassembly Petri net model is demonstrated through the sample disassembly of a flashlight.