Optimally locating in-house logistics areas to facilitate JIT-supply of mixed-model assembly lines

In modern-day production systems, ever-rising product variety poses a great challenge for the internal logistics systems used to feed mixed-model assembly lines with the required parts. As an answer to this challenge many manufacturers especially from automobile industries have identified the supermarket-concept as a promising part feeding strategy to enable flexible small-lot deliveries at low cost. In this context, supermarkets are decentralized in-house logistics areas in the direct vicinity of the final assembly line, which serve as intermediary stores for parts. Small tow trains are loaded with material in a supermarket and deliver parts Just-in-Time to the stations lying on their fixed route. This paper discusses the general pros and cons of the supermarket-concept and treats the decision problem of determining the optimal number and placement of supermarkets on the shop floor. A mathematical model is proposed, an exact dynamic programming algorithm presented, and the validity of the proposed approach for practical purposes as well as the trade-off resulting from fixed installation and maintenance cost is investigated in a comprehensive computational study.     

Job rotation in assembly lines employing disabled workers

In this paper we consider the programming of job rotation in the assembly line worker assignment and balancing problem. The motivation for this study comes from the designing of assembly lines in sheltered work centers for the disabled, where workers have different task execution times. In this context, the well-known training aspects associated with job rotation are particularly desired. We propose a metric along with a mixed integer linear model and a heuristic decomposition method to solve this new job rotation problem. Computational results show the efficacy of the proposed heuristics.     

Hybrid heuristics for planning job rotation schedules in assembly lines with heterogeneous workers

We investigate the problem of balancing assembly lines with heterogeneous workers while considering job rotation schedules. This problem typically occurs in assembly lines in sheltered work centers for disabled. We propose a hybrid algorithm that uses a Mixed Integer Programming (MIP) to select appropriate schedules from a pool of heuristically constructed solutions. A local search based on MIP neighborhoods is used as a post-optimization method. Our results show that this approach is fast, flexible and accurate when compared with current available methods.     

Maximizing production rate and workload smoothing in assembly lines using particle swarm optimization

Particle swarm optimization (PSO) one of the latest developed population heuristics has rarely been applied in production and operations management (POM) optimization problems. A possible reason for this absence is that, PSO was introduced as global optimizer over continuous spaces, while a large set of POM problems are of combinatorial nature with discrete decision variables. PSO evolves floating-point vectors (called particles) and thus, its application to POM problems whose solutions are usually presented by permutations of integers is not straightforward. This paper presents a novel method based on PSO for the simple assembly line balancing problem (SALBP), a well-known NP-hard POM problem. Two criteria are simultaneously considered for optimization: to maximize the production rate of the line (equivalently to minimize the cycle time), and to maximize the workload smoothing (i.e. to distribute the workload evenly as possible to the workstations of the assembly line). Emphasis is given on seeking a set of diverse Pareto optimal solutions for the bi-criteria SALBP. Extensive experiments carried out on multiple test-beds problems taken from the open literature are reported and discussed. Comparisons between the proposed PSO algorithm and two existing multi-objective population heuristics show a quite promising higher performance for the proposed approach.     

Advantages of assembly lines in Sheltered Work Centres for Disabled. A case study

Current practices for the treatment of the physically and/or mentally handicapped prescribe meaningful job activity as a means towards both a more fulfilling life and societal integration. In many countries, these practices have facilitated the development of many Sheltered Work Centres for Disabled.In the case study presented, a reengineering process is done starting from individual workplaces where only certain workers were capable of assembling the entire product, and finishing with an assembly line implementation. It is revealed how the traditional division of work in single tasks, typical in assembly lines, becomes a perfect tool for making certain worker disabilities invisible, providing new jobs for disabled people; always taking into account certain special constraints that are analysed.     

A comparison of search techniques for minimizing assembly time in printed wiring assembly

In the robotics assembly of DPP model, the coordinates of assembly point and magazine are dynamically changed during robotics assembly so that evaluation of the assembly efficiency is extremely complicated. To route the robotics travel, most related investigations have utilized the fixed coordinate of insertion points and magazine using the Traveling Salesman Problems (TSP) method to sequence the insertion points after arbitrarily assigning the magazine. However, robotics travel routing should be based on a relative coordinate to obtain a better solution because the robotics, board and magazine are simultaneously moved at different speeds during assembly. To resolve such a dynamically combinatorial problem, this study presents the Genetic Algorithm (GA), Simulated Annealing (SA), and Tabu Search (TS) based algorithms. These approaches can simultaneously arrange the insertion sequence and assign the magazine slots by the computer and yield a better performance compared to the conventional approach. Results presented herein also demonstrate that the larger the number of insertion points and/or part numbers the better the performance. These approaches are also compared.     

Best-matching protocols for assembly in e-work networks

Assembly networks pose many challenges to the comprising businesses due to their ever-growing distributed nature. This article explores the benefits of incorporating best-matching protocols (BMP) into the principles of design for assembly (DFA) to make better use of already existing information on equipment, parts and suppliers. Best-matching protocols for cooperation requirement planning (BMP-CRP), for part matching (BMP-part) and supplier selection were developed. A case study for the matching of parts and suppliers is provided. The results of the case study corroborate the benefits in quality and costs that the best-matching protocols can yield for businesses in an assembly e-work network.     

Micro-dispersion of performance across industry lines

Classical industrial organization suggests that profitability differences are caused by industry-specific factors. Revisionist and managerial approaches, however, are stressing the predominant importance of firm-specific factors. Empirical evidence is more pronounced for firm-related factors, but recent inquiry also found support for the superiority of industry effects. The present paper examines the discriminating power of the industry variable to separate a German firm sample into homogeneous industry subgroups. The finding is that the industry does not have a significant influence on the dispersion of firm profit rates. Thus, the firm-effect approach to profitability is corroborated.     

流水工序调度与生产效率的关系模型分析

提出一种基于粒子群算法的流水工序调度任务优化模型。利用流水工序调度任务的特点得到流水工序时间约束条件,利用粒子群算法的原理建立流水工序调度任务优化模型,利用粒子群算法对模型进行求解。仿真实验表明,利用该算法能够得到流水工序调度问题的最优解,提高生产效率。     

Analytical analysis of a generic assembly system

The assembly of components is a key element in manufacturing facilities. Nevertheless, literature analyzing the dynamic behavior remains scarce. The paper narrows this gap by studying a generic first-come first-serve assembly system, consisting of two generally distributed component input streams. The field of probability theory serves as a means to derive good approximations for the waiting time of the components to form a kit and the inter-arrival time of the kits at the assembly station. Apart from providing insight in generally accepted managerial principles, this analysis also constitutes a required step in obtaining the performance of an open queuing network including assemblies.     

On lemons and indigestibility: resource assembly through joint ventures

We revisit the relationship between two theoretical perspectives on joint ventures—the asymmetric information view and the indigestibility view. The former emphasizes the ex ante valuation challenges firms confront in combining resources, while the latter attends to ex post transaction costs arising from the extraction and integration of indivisible resources. We argue that these two views are complementary, rather than competing, in explaining the usefulness of joint ventures. We also suggest that the perspectives are overlapping inasmuch as resource indivisibility contributes to asymmetric information. Copyright © 2000 John Wiley & Sons, Ltd.     

同舟共济共谋发展 澄海玩具协会四届二次会员大会隆重举行

2009年3月27日下午，汕头市澄海区玩具协会在澄海花园酒店举行“澄海玩具协会四届二次会员大会”，出席大会的有澄海玩具协会全体会员代表、名誉会长和顾问，“中国玩具礼品城——澄海展示交易中心”的常年展商列席，汕头市澄海区常务副区长柯茂出席，并代表区委、区政府作重要讲话，澄海玩具协会会长郭卓才作工作报告，澄海玩具协会副会长介绍新增副会长名单和宣布聘请副秘书长，澄海展览中心总经理王文璧介绍第11届澄海玩具博览会和常年展的优惠措施，天瑞（中国）仪器有限公司介绍玩具检测仪器，广东省玩具协会介绍“澄海国际玩具品牌推介方案”，澄海玩具协会秘书长蔡杰臣支持会议。     

Design of the optimal feeding policy in an assembly system

This paper describes an innovative and integrated approach to component management optimization within a production/assembly system. In a mixed-models assembly process the handling of parts and components for each work station represents a substantial variable that can greatly affect job duration and efficiency. This paper is strictly related to Assembly to Order/Manufacturing to Order (ATO and MTO) systems, where lead time has to be very short and flexibility is at its maximum level. In Assembly to Order (ATO) or Make to Order (MTO) systems, the production is increasingly getting more customized in response to the demand, thanks to the progresses reached in both manufacturing and information technologies. It is becoming increasingly possible to assemble or make products specifically in response to the requests of either end customers or retailers. As a consequence of such customization, the design of the whole system must take into direct account several elements: parts warehouses location, feeding policies and feeding systems. In some cases the collection of parts and components required picking activities, in other the movement of entire units load.In several instances experts have analyzed the problems about material centralization/decentralization, storage policies and assembly feeding problem in different and independent ways, while the problem needs an integrated approach. While many researches regarding components allocation problems in ATO and MTO systems, did not consider feeding policies, material picking, packing activities and vehicles optimization, this paper cover focuses on filling such gap using an integrated framework that considers both aspects of the problem: the centralization/decentralization of components in order to minimize the total storage costs and the right feeding policies.Feeding problems in assembly lines are some of the most important aspects to consider during the analysis and design of an assembly system, to allow the maximization of efficiency and flexibility. To reach such goals, a multi-factorial analysis has been carried out during this experiment and will validate the introduced framework. An industrial application of the introduced framework is illustrated to explain its real significant production implication.     

铜材料在输电线路防雷接地中的应用

针对处于沿海盐碱地质等地区的输电线路接地电阻易受腐蚀的问题,提出采用一种新型镀铜接地装置作为输电线路接地电阻的新方法,并应用于生产实际中。通过分析新材料在接地系统中应用的各项效益指标,并与之前传统的接地电阻进行对比,可知利用镀铜作为接地电阻材料,能有效地减少由于雷击而接地电阻不满足要求造成输电线路跳闸的故障,为电力系统的安全稳定运行提供可靠保障。     

Backup strategy for robots’ failures in an automotive assembly system

Automotive assembly lines are often characterized by robots’ failures that may result in stoppages of the lines and manual backup of tasks. The phenomena tend to impair throughput rate and products’ quality. This paper presents a backup strategy in which working robots perform tasks of failed robots. The proposed Mixed-Integer Linear-Programming based approach minimizes the throughput loss by utilizing the robots’ redundancy in the system. Two algorithms are developed to comply with stochastic conditions of a real-world environment. The performance of these algorithms is compared with several heuristics, and the downstream-backup based algorithm is found superior to all other methods.     

Ant colony optimization for the single model U-type assembly line balancing problem

An assembly line is a production line in which units move continuously through a sequence of stations. The assembly line balancing problem is defined as the allocation of tasks to an ordered sequence of stations subject to precedence constraints with the objective of optimizing a performance measure. In this paper, we propose ant colony algorithms to solve the single-model U-type assembly line balancing problem. We conduct an extensive experimental study in which the performance of the proposed algorithm is compared against best known algorithms reported in the literature. The results indicate that the proposed algorithms display very competitive performance against them.     

避免键联接产生装配干涉的公差设计方案

分析了键联接进行装配时产生干涉的具体情况,介绍了保证键联接顺利装配的2种公差设计方案,并对各方案的含义、图样标注和应用特点进行了介绍。     

Scheduling a multi-stage fabrication shop for efficient subsequent assembly operations

Consideration is given to scheduling the operation of a multi-stage fabrication shop producing the component parts of a major commercial refrigerators producer. The objective of this scheduling problem is the determination of both production sequences and lot quantities at each stage so as to meet production targets and ensure continuous operation of subsequent assembly stations. After describing the problem within its natural context, we present an algorithm for the dynamic scheduling of the fabrication shop. This applies general planning principles adapted to the needs of the environment under consideration and makes use of existing heuristic rules for arriving at sequencing decisions. Although in no sense optimal, the algorithm can provide good feasible solutions to a previously not formally analysed problem. After being incorporated into a systematic computer-aided scheduling procedure, the algorithm has been actually implemented, demonstrating considerable improvements over previous fabrication shop scheduling practice.     

U-shaped production lines: A review of theory and practice

Most writers describe the U-shaped production line as the special type of cellular manufacturing used in just-in-time (JIT) production systems. JIT is defined to be an umbrella term for a number of techniques whose purpose is to improve product quality and cost by eliminating all waste in the production system. The U-line arranges machines around a U-shaped line in the order in which production operations are performed. Operators work inside the U-line. One operator supervises both the entrance and the exit of the line. Machine-work is separated from operator-work so that machines work independently as much as possible. Standard operation charts specify exactly how all work is done. U-lines may be simple or complex. U-lines are rebalanced periodically when production requirements change. The U-line satisfies the flow manufacturing principle. This requires operators to be multi-skilled to operate several different machines or processes. It also requires operators to work standing up and walking. When setup times are negligible, U-lines are operated as mixed-model lines where each station is able to produce any product in any cycle. When setup times are larger, multiple U-lines are formed and dedicated to different products. 114 US and Japanese U-lines are examined in this study. The average U-line has 10.2 machines and 3.4 operators. About one-quarter of all U-lines are manned by one operator and so run in chase mode. The reported benefits are impressive. Productivity improved by an average of 76%. WIP dropped by 86%. Leadtime shrunk by 75%. Defective rates dropped by 83%.     

A method for reducing inter-departure time variability in serial production lines

The inter-departure time variability is an important measure in production lines. Higher variability means added work-in-process and less predictability in output. It can be a primary obstacle towards achieving on-time delivery. The effects of line parameters (e.g., line length or buffer capacity) on inter-departure time variability have been studied in recent years but no method has been proposed for its reduction. In this paper, such a strategy is proposed and studied via simulation. Results indicate that significant reductions (of more than 20%) in inter-departure time variability can be achieved for as little as 0.5% increase in the mean inter-departure time or without any increase at all, for a majority of the line parameter values experimented. This was found to be the case for symmetrical (uniform) processing time distributions as well as for asymmetrical skewed (exponential) distributions. Similar results have also been obtained in the application of the proposed strategy for the case when one station has a higher variance than the others. Therefore, in situations where output predictability is more of a problem than capacity, this strategy constitutes an effective alternative.