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.     

A bill of materials-based approach for end-of-life decision making in design for the environment

Re-use, recycling or remanufacturing of products and components are good alternatives for reducing the environmental problems resulting from the huge amounts of waste currently arriving at landfills. A new approach is proposed in this paper for enhancing these alternatives from the earliest stages of product design. Given the product structure (obtained from its bill of materials (BOM)) and the joining and geometrical relationships among the components (obtained from the three-dimensional, computer-aided design representation), a model is proposed that will determine the EOL (EOL) strategy, i.e. the depth of disassembly inside the structure and the final end (re-use, recycle, remanufacture or disposal) for each disassembled part leading to the highest profit. A scatter search (SS) metaheuristic is used to determine the disassembly cost at each level of the BOM. The model presents a number of major improvements with respect to previous research. It addresses the problems of simultaneously determining both the best EOL strategy and the disassembly sequence, as well as allowing removal of components not only over the two or three Cartesian axes and affording the possibility of modifying the encountered strategy in a further step so as to fulfil other business criteria (such as disassembly time, resources availability or maximum waste generation rate).     

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.     

基于模糊推理的不确定环境下拆卸工艺规划

回收产品因磨损等原因其结构和质量会发生改变,拆卸序列规划存在不确定性,拆卸前很难确定产品最优拆卸序列。首先建立一个模糊拆卸Petri网模型表示产品可行拆卸序列和拆卸过程存在的不确定信息,为降低产品质量和拆卸能力的不确定性对拆卸序列优化的影响,建立一个自适应的模糊推理系统,利用模糊推理和反馈学习的方法对产品各拆卸步骤的成本进行预测,然后通过计算不同拆卸序列下拆卸的收益来得到产品最优拆卸序列,最后通过算例证明了方法的有效性。     

Dynamic disassembly planning for remanufacturing of multiple types of products

With the increased need for remanufacturing of end-of-life products, achieving economic efficiency in remanufacturing is urgently needed. The purpose of this study was to devise a cost-minimisation plan for disassembly and remanufacturing of end-of-life products returned by consumers. A returned end-of-life product is disassembled into remanufacturable parts, which are supposed to be used for new products after being remanufactured. Each end-of-life product is disassembled into parts at variable levels and through variable sequences as needed, taking into account not only disassembly but also manufacturing, remanufacturing, and holding inventory of remanufacturable parts. This study proposes a mixed integer linear programming (MILP) model for derivation of the optimal disassembly plan for each returned product, under deterministically known demand and return flows. For the purposes of an illustrative example, the proposed model was applied to the formulation of an optimal disassembly and remanufacturing plan of ‘fuser assembly’ of laser printers. The solution reveals that variable-level disassembly of products saves a significant remanufacturing cost compared with full disassembly.     

Planning product disassembly for material recovery opportunities

This paper addresses an increasingly important aspect of product design and its relationship to life-cycle costing: disassembly for material recovery opportunities (MRO). MRO is defined as an opportunity to reclaim post-consumer products for recycling, remanufacturing and re-use. The authors have developed a methodology which can be used to identify and assess cost-effective characteristics of disassembly for the recovery of products. The central focus of this paper is aimed at improving the efficiency of the disassembly planning process and generating an optimal disassembly sequence. Four criteria are established to optimize the generation of the disassembly sequence: (1) material compatibility, (2) clustering for disposal, (3) concurrent disassembly operations, and (4( maximizing yield. In this paper we define the ‘disassemblability’ of a product as the ability to optimize the design and disassembly process for removal of specific pans or materials in a manner which will minimize costs. Steps have been taken to incorporate this methodology within a life-cycle analysis software tool (EDIT) to be used at the early concept stage of product design.     

Using V-A-T analysis for determining the priority and location of JIT manufacturing techniques

V-A-T analysis is a procedure which categorizes manufacturing operations based upon the nature of product flow via the structure of the routeings and bill of materials. The letters V, A, and T stand for the shape of the dominant product routeings and bill of material structures within a manufacturing facility. The purpose of this article is to examine the possibility of using V-A-T analysis as an aid in JIT implementation. Contained in this paper is: an examination of the evolution of JIT manufacturing in Japan, and its introduction to the United States; an analysis of the various techniques constituting JIT; implementation issues regarding JIT; and an examination of V-A-T analysis as a tool for JIT implementation.     

Applying data mining technique to disassembly sequence planning: a method to assess effective disassembly time of industrial products

Design for end-of-life and design for disassembly are enabling design strategies for the implementation of business models based on the circular economy paradigm. The paper presents a method for calculating the effective disassembly sequence and time for industrial products. Five steps support designers in defining liaisons and related properties and precedence among components with the aim to calculate the best disassembly sequence and time. The effective disassembly time is computed considering the actual conditions of a product and its components (e.g. deformation, rust and wear) using corrective factors. This aspect represents the main contribution to the state of the art in the field of design for disassembly. The corrective factors are derived from a specific data mining process, based on the observation of real de-manufacturing activities. The proposed approach has been used for calculating the disassembly times of target components in a washing machine and in a coffee machine. The case studies highlight the method reliability of both: definition of time-effective disassembly sequences and assessment of effective disassembly times. In particular, a comparison of experimental tests shows a maximum deviation of ?6% for the electric motor of the washing machine and ?3% for the water pump of the coffee machine.     

Integrated assembly and disassembly sequence planning using a GA approach

In a product life cycle, an assembly sequence is required to produce a new product at the start, whereas a disassembly sequence is needed at the end. In typical assembly and disassembly sequence planning approaches, the two are performed as two independent tasks. In this way, a good assembly sequence may contradict the cost considerations in the disassembly sequence, and vice versa. In this research, an integrated assembly and disassembly sequence planning model is presented. First, an assembly precedence graph (APG) and a disassembly precedence graph (DPG) are modelled. The two graphs are transformed into an assembly precedence matrix (APM) and a disassembly precedence matrix (DPM). Second, a two-loop genetic algorithm (GA) method is applied to generate and evaluate the solutions. The outer loop of the GA method performs assembly sequence planning. In the inner loop, the reverse order of the assembly sequence solution is used as the initial solution for disassembly sequence planning. A cost objective by integrating the assembly costs and disassembly costs is formulated as the fitness function. The test results show that the developed method using the GA approach is suitable and efficient for the integrated assembly and disassembly sequence planning. Example products are demonstrated and discussed.     

Disassembly sequence generation: A Petri net based heuristic approach

The generation of a set of optimal or near-optimal disassembly sequences is an important task associated with the study of disassembly planning. This task encapsulates actions at the required disassembly depth to reach maximum net revenue while satisfying economic constraints. The Petri net modelling, combined with heuristic search procedures developed in this study, offers an efficient procedure for disassembly sequence generation. The heuristic generates and searches a partial reachability graph to arrive at an optimal or near-optimal disassembly sequence based on the firing sequence of transitions of the Petri net model. The proposed methodology reduces the search space in two areas: (1) pruning the disassembly tree (DT) and, (2) selective tracking of the reachability graph. The efficacy of the proposed methodology is demonstrated by using two examples from the literature.     

Interactive AR-assisted product disassembly sequence planning (ARDIS)

This paper presents a proof-of-concept novel near real-time interactive AR-assisted product disassembly sequence planning system (ARDIS) based on product information, such as interference matrix and 3D models. The system is developed using Unity and consists of three modules, including an intelligent disassembly sequence planning module, an automatic content authoring module and an intuitive augmented reality (AR) user interface (UI) with various features, such as a virtual panel for customisation and an option panel for sequence regeneration. Given the retrieval targets specified by a user, optimised disassembly sequences are computed using an evolutionary computing algorithm. For the sequences computed, the respective AR disassembly instruction sequences, such as 2D text instructions and animated 3D models, are generated dynamically based on a taxonomy that links each disassembly step in a sequence with the corresponding Unity templates that have been created beforehand. Hence, the need for manual authoring to provide AR disassembly guidance is reduced. If necessary, the user can request for alternative disassembly sequences which can be re-computed in near real-time. Several case studies have been carried out to demonstrate and evaluate the performance of the system within the laboratory environment.     

Quality control of an unreliable random FMS: with Bernoulli and CSP sampling

It is widely recognized that disassembly-based product End-of-Life strategies, such as component reuse or simple fraction material recycling, are environmentally beneficial. However, current disassembly costs hinder a widespread application of these strategies. This paper quantifies the disassembly time reductions required to achieve economic feasibility of systematic product disassembly. A modelling framework, based on linear programming, is used to investigate the effect of reducing the expected disassembly time and cost on the selection of the optimal End-of-Life strategy. The problem is optimized from an End-of-Life treatment facility point of view. All findings are based on the Belgian cost and price information captured in spring 2004. The linear programming model shows that for small products from the Waste of Electric and Electrical Equipment (WEEE) category disassembly-based End-of-Life strategies will hardly become optimal, while for medium- and large-sized products, this scenario can be made optimal if a substantial disassembly time reduction is achieved. Possible strategies to realize such reduction are briefly sketched.     

Modelling material separation processes in bulk recycling

Increasing environmental concerns about the disposal of mass produced products have resulted in efforts to recover value from components and materials before discarding such products. Methods include incineration, disassembly or de-manufacturing and bulk recycling. This paper investigates several cases of the problem of selecting the best sequence for recovery of materials by bulk recycling. A solution procedure for determining the optimal sequence for isolating all target materials present in a given batch based on dynamic programming is presented. A modification for targeting specific materials in a batch is discussed. Additional constraints arising from the operation of such facilities are also discussed. The general problem of target material identification is presented and a procedure for selecting a profitable target material mix, along with a numerical illustration, is documented. Finally, the integrated consideration of bulk recycling and disassembly for evaluating product disposal costs is presented.     

Joint product variety,pricing and scheduling decisions in a flexible facility

This paper studies a manufacturer’s optimal product variety, pricing and scheduling decisions in a single flexible production facility when customers have private information in their marginal valuations for product qualities. In addition to determining the product variety and price of each product, the manufacturer needs to optimise a detailed schedule of production (batch sizes and production sequences) to fully utilise the flexibility of this facility. To achieve the second-degree discrimination, the manufacturer provides multiple products and follows a priority rule in the production schedule. To obtain economies of scale, the manufacturer may offer a composite product targeting the whole population, or choose a dedicated product to serve a proportion of customers. Comparing these three production choices, we observe that the optimal product variety strategy is threshold controlled by the relative ratio of customer arrival rates, the relative difference between customers’ marginal valuations and the production technology.     

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.     

Analyzing the effects of inventory cost setting rules in a disassembly and recovery environment

In this study we consider a disassembly and recovery facility receiving end-of-life products and facing demand for a specific part that is disassembled from the product and then recovered. The disassembly and recovery operations can be either performed before hand, or upon customer arrival. In the latter case, a discount on the selling price is applied to compensate the customer for waiting for the completion of the disassembly and recovery operations. One of the difficulties faced in planning for such a system is the determination of the opportunity cost associated with carrying recovered parts inventory. The difficulty arises in seeking the value added to the part given the costs incurred for maintaining the product return, disassembly and recovery costs and revenue earned from the hulk, that is the remaining product after the disassembly of the part. The main objective of the study is to investigate the effect of different rules to determine this opportunity cost on the performance of the system. Six rules are considered in the study. The performance of the rules is assessed by a computational study under an approximate inventory control policy.     

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.     

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.