装配类小微的流水线价值流分析与精益改善研究

在"企业集团小微化"背景下,针对装配类小微的生产现状,构建融合DMAIC(Define,Measure,Analysis,Improve,Control)过程的价值流分析模型(DMAICVSM),并在建立价值流成熟度模型的基础上,利用BP神经网络进行价值流成熟度评定.以当前价值流成熟度为改进起点,以未来价值流成熟度为改进目标,量化改进空间并规划成熟度进化路线,达成对装配线的持续改进.结合某装配类小微的生产实际,验证了DMAIC-VSM的可行性.     

企业精益改造的道路

本文探讨了成组精益生产的概念,对过去阶段利用成组技术进行技术改造进行了反思,提出在当前对企业进行内涵式精益改造的方法与措施。     

企业CD段流水线的瓶颈分析与平衡改善

在生产线平衡原理及改善方法的基础上,以工作测定为依据,分析了企业CD段流水线的工作能力及其平衡状况,针对整条流水线的瓶颈,结合生产线实际情况提出了可行的持续改进方案,并对改进前后的方案进行了对比分析,达到了降低瓶颈工位工作时间、提升流水线平衡性、提高产能的目的,实际效果明显.     

基于JIT的流水线生产效率提升方法研究

以某线缆自动生产线为研究对象,针对生产线不均衡、在制品库存量大、生产效率不能满足客户需求等问题,提出了基于JIT的改善方案。灵活运用山积表、物与信息流动图等工具对生产线进行分析,改善后生产线平衡率由原来的70.97%提高到83.3%,并将看板方式引入该生产线,实现拉动生产,生产过程周期(Lead Time)由原来的19.1天降低到7.6天。     

基于市场需求变化的流水线最佳生产节拍选择

以精益思想为指导,以选择最佳流水线生产节拍为目标,建立了单台相关制造成本模型,并以其为基础,面对市场的实际需求变化,提出了装配线设计阶段最佳生产节拍的选择方法,以及面对市场波动时改线方案的选择方法。通过实例对研究进行了验证。     

ProModel的服装缝制流水线仿真及应用

对S公司的服装缝制流水线编排情况进行研究,建立了基于ProModel的仿真模型.将仿真模型运行情况与实际情况进行对比,确定模型的有效性,并运用该模型运行结果分析实际流水线生产情况,有针对性地提出改进措施并仿真,根据仿真结果对流水线进行了优化.结果表明,在考虑和处理诸如回修、搬运等因素的影响时,仿真方法相比手工编制方法具有明显的优势,有利于企业更有效地提高流水线的生产效率和实现对生产进度的准确把握.     

浅谈桁架结构超声波检测方法研究

随着当代建筑技术日新月异,空间管桁架结构在当代建筑中使用率越来越高。采用超声波检测的手段对焊缝进行质量检验是确保工程质量的重要环节。本文从外部焊缝缺陷、内部焊缝缺陷等方面对钢结构超声波探伤做了初步探讨。     

基于流水线的FFT快速计算方法与实现技术

针对目前CDMA快速码捕获系统对捕获速度要求越来越高,在分析快速傅里叶算法理论的基础上,结合FPGA(Field Programmable Gate Array)的独特硬件结构,提出一种基于流水线的FFT(Fast Fourier Transform)快速实现方法,并对该方法进行了matlab仿真、ISE仿真和FPGA实验.研究结果证明:相比于传统的FFT实现方法,在保证计算精度的基础上,该方法实现了FFT计算数据的连续输入与输出.减小了捕获时延,缩短了至少1/3的计算时间,在100 MHz时钟时,完成4096点的FFT运算只需要42.05μs,为高速信号处理系统提供了一种更好的时频转换方法.     

某高层建筑双层钢桁架整体提升施工技术

本文以某工程2号塔楼西侧钢桁架整体提升施工为例,通过在每片桁架立面设置两件临时斜撑,上弦杆端头设置水平横撑,使主桁架形成“整体稳定体系”,同时整个钢桁架形成刚性整体结构,解决了钢桁架整体提升的同步协调性问题,提高了施工效率,保证了施工质量和安全。     

基于位置加权法的包装流水线平衡

目的研究某企业电动铅笔刨包装生产线工序优化与生产线平衡。方法应用工业工程分析方法,对企业的原生产线及流程进行改造,根据电动铅笔刨包装生产线的生产工艺特点,运用生产流水线平衡的位置加权法合理调整生产工序,同时对作业内容、作业人员和设备及设施布置进行重新分配和调整。结果与原生产线方案相比较,平衡后电动铅笔刨包装生产线流水线平衡率提高了31%,流水线作业人员减少4人,提高了订单交付水平,生产线布局保证了生产过程的流畅性,满足了计划产量生产要求。结论采用位置加权法,结合工序优化、分解与合并,可以获得较好的生产流水线平衡效果。     

A framework for the continuous performance improvement of manned assembly lines

This paper proposes a framework for the continuous performance improvement of manned assembly lines for major appliances. The suggested framework consists of two main activities: (1) assembly work process improvement, including time and motion study and (2) improvement of line balance efficiency. Although there have been numerous studies on this topic, most of them deal with partial issues rather than the continuous performance improvement of the whole assembly line, which this paper addresses. To develop the framework, we categorised a manned assembly line into five analysis levels, (workstation, worker, operation cycle, work element and unit motion), and identified user requirements on each level. Among these five analysis levels, the workstation level supports line balancing, while the other four (worker, operation cycle, work element and unit motion) address work process improvement. The proposed framework has been implemented and tested with various examples from Korean assembly line based manufacturers.     

A priority rule-based constructive heuristic and an improvement method for balancing assembly lines with parallel multi-manned workstations

Assembly lines of big-size products such as buses, trucks and helicopters are very different from the lines studied in the literature. These products’ manufacturing processes have a lot of tasks most of which have long task times. Since traditional assembly line models including only one worker in each station (i.e. simple assembly lines) or at most two workers (two-sided assembly lines) may not be suitable for manufacturing these type of products, they need much larger shop floor for a number of stations and long product flow times. In this study, an assembly line balancing problem (ALBP) with parallel multi-manned stations is considered. Following the problem definition, a mixed integer programming formulation is developed. A detailed study of priority rules for simple ALBPs is also presented, and a new efficient constructive heuristic algorithm based on priority rules is proposed. In order to improve solutions found by the constructive heuristic, a genetic algorithm-based solution procedure is also presented. Benchmark instances in the literature are solved by using the proposed mathematical programming formulation. It has been seen that only some of the small-size instances can be solved optimally by this way. So the efficiency of the proposed heuristic method is verified in small-size instances whose optimal solutions are found. For medium- and big-size instances, heuristics’ results and CPU times are demonstrated. A comparative evaluation with a branch and bound algorithm that can be found in the literature is also carried out, and results are presented.     

Using distributed search methods for balancing mixed-model assembly lines in the automotive industry

Currently, modern companywide PC networks usually possess significant unused calculation capacity. Since the connected personal computers are mainly used for office applications, considerable off-peak times occur. Consequently, in order to solve planning problems more efficiently, it is promising to apply distributed search procedures that make use of those available off-peak times. This applies in particular to complex problems where insights into the structure of the solution space are lacking. The paper at hand illustrates the application of distributed search methods to automotive assembly line balancing. Modern mass customization programs in the automotive industry frequently comprise more than a billion theoretical variants. Since this causes an oscillating capacity demand at the line, deliberately designing the layout of a mixed-model assembly line is of significant importance. The paper at hand provides a new mixed-model assembly line balancing approach that integrates specific aspects relevant for the automotive industry. However, by integrating several -hard subproblems like a detailed personnel planning or a flexible process planning of each task, the resulting model has significant complexity. Consequently, in order to find appropriate line layouts in reasonable time, specifically designed distributed solution approaches are provided and evaluated. Among these approaches, particularly the use of a specific clustered Tabu Search algorithm attains promising results. By making use of an adaptive dynamic load balancer, substantial improvements of the solution quality can be obtained even under unfavorable circumstances like oscillating background loads in the PC network.     

Balancing mixed-model assembly lines with adjacent task duplication

When a mixed-model assembly line (MAL) is balanced, it is generally assumed that the variants of a task over different models should be assigned to an identical station. In this study, this restriction is relaxed and the variants of a task over different models can be duplicated on two adjacent stations (referred to as adjacent task duplication) to improve the MAL’s efficiency. The adjacent task duplication incurs few additional training and tool duplication costs as each task is duplicated on at most two stations. Moreover, for each task, the assembly part storage is not duplicated as it can be shared by the two adjacent stations. The mathematical model of this problem is formulated and some important properties are characterised. A branch, bound and remember algorithm is then developed to solve the problem. The performance of the proposed algorithm is tested on 900 representative instances, of which 889 instances are optimally solved. The experimental results show that the use of the adjacent task duplication policy effectively reduces the number of stations, especially when the WEST ratios are small.     

Balancing two-sided assembly lines with sequence-dependent setup times

Two-sided assembly lines are often designed to produce large-sized products, such as automobiles, trucks and buses. In this type of production line, both left-side and right-side of the line are used in parallel. In all studies on two-sided assembly lines, sequence-dependent setup times have not yet been considered. However, in real life applications, setups may exist between tasks. Performing a task directly before another task may influence the latter task inside the same station, because a setup for performing the latter task may be required. Furthermore, if a task is assigned to a station as the last one, then it may cause a setup for performing the first task assigned to that station since the tasks are performed cyclically. In this paper, the problem of balancing two-sided assembly lines with setups (TALBPS) is considered. A mixed integer program (MIP) is proposed to model and solve the problem. The proposed MIP minimises the number of mated-stations (i.e., the line length) as the primary objective and it minimises the number of stations (i.e., the number of operators) as a secondary objective for a given cycle time. A heuristic approach (2-COMSOAL/S) for especially solving large-size problems based on COMSOAL (computer method of sequencing operations for assembly lines) method is also presented. An illustrative example problem is solved using 2-COMSOAL/S. To assess the effectiveness of MIP and 2-COMSOAL/S, a set of test problems are solved. The computational results show that 2-COMSOAL/S is very effective for the problem.     

Redundant configuration of robotic assembly lines with stochastic failures

One of the main challenges in the operation of robotic assembly lines is the occurrence of failures. Due to the connection of the stations via a material handling system, failures at one station often result in throughput losses. To some extent, these throughput losses can be reduced by installing buffers between the stations. However, the installation of buffers requires considerable investments and scarce factory space. Due to the advances of manufacturing technologies that form the foundation of ‘Industry 4.0’, new solutions to reduce failure-related throughput losses open up. One solution is a redundant configuration, in which downstream (backup) stations automatically take over the operations of failed stations during repair time. The throughput loss in these situations depends on the allocation of operations and the assignment of backup stations. Existing approaches in the literature that consider redundancies in the configuration of automated lines neglect the resulting production rate. Instead, the lines’ level of redundancy is used as a surrogate measure for optimisation. We present a genetic algorithm for the redundant configuration of robotic assembly lines with stochastic failures to maximise the production rate of the line. In a numerical analysis, it is demonstrated that this approach allows for productivity improvements.     

Analysis of truss structures using distributed object-oriented methods

Objected-oriented analysis methods are developed for distributed finite element analysis of truss structures. The method is based on distributed solution of finite element equations using the substructuring method. Objects for static analysis of truss structures are identified and presented in a pseudocode form. The developed techniques are implemented in a network of workstations. A software tool called the IDL-C++ (RPC) compiler has been developed to aid the programmer in constructing distributed object applications. The speedup/performance for moderate size problems is presented to illustrate the present approach for truss analysis using distributed object-oriented methods.     

Free-transfer lines with unreliable assembly stations and small buffers

This paper describes the arrangement in series of assembly stations that are linked by storage places. The distribution of the stations and of the number of places in the stocks affects the efficiency of the assembly. The results of the continuous model show that grouping stations by two or three does not improve the effectiveness of the line when the number of places is limited. On the other hand, the discrete synchronous model proved that it is profitable to group stations when a low capacity of storage is experienced; these results have been confirmed using a simulation software which processes the components in a discrete manner.     

Sequencing mixed-model assembly lines operating with a heterogeneous workforce

We study the problem of sequencing mixed-model assembly lines operating with a heterogeneous workforce. The practical motivation for this study comes from the context of managing assembly lines in sheltered work centres for the disabled. We propose a general framework in which task execution times are both worker and model dependent. Within this framework, the problem is defined and mathematical mixed-integer models and heuristic procedures are proposed. These include a set of fast constructive heuristics, two local search procedures based on approximate measures using either a solution upper bound or the solution of a linear program and a GRASP metaheuristic. Computational tests with instances adapted from commonly used literature databases are used to validate the proposed approaches. These tests give insight on the quality of the different techniques, which prove to be very efficient both in terms of computational effort and solution quality when compared to other strategies such as a random sampling or the solution of the MIP models using a commercial solver.     

Research on a JIT scheduling problem in parallel motorcycle assembly lines considering actual situations

After the research of schedule problem of one kind of flexible motorcycle assembly lines, a kind of parallel conveyor belt flow shop schedule model using JIT (just-in-time) is given. The impacts of the different max process paces of different work pieces in different stations are considered. Besides, some actual situations, including unstable information and structural constrain, are also considered. Then a kind of improved artificial fish swarm algorithm based on polar coordinate coding is presented to optimise this schedule model. Lastly, this model is tested with the real data from two motorcycle assembly lines, and the result shows that the total production fee is reduced.