Classification and modeling for in-plant milk-run distribution systems

Material handling is one of the most important issues that should be taken into account for eliminating waste and reducing the cost. It is one of the seven wastes defined in the concept of lean manufacturing. In this study, for a lean material handling system under the lean manufacturing conditions such as pull-based and repetitive manufacturing, a system consisting of periodically moving vehicles in certain routes is taken into consideration. This system is also called milk-run distribution system. Application of milk-run distribution systems in plants standardizes the material handling system and eliminates the waste. Although there are huge numbers of studies related with inbound and outbound logistics, there are few studies especially related with milk-run applications in the manufacturing area. Within this study, based on the observations in real manufacturing environment and limited literature, the milk-run distribution problem in the plants is categorized and explained. For one of the main categories, modeling is performed. The objective of the developed models is to minimize the number of vehicles and the distance traversed. A numerical example inspired by real applications is presented for showing the applicability of the developed models.     

Design of a just-in-time periodic material supply system for the assembly lines and an application in electronics industry

The purpose of the paper is the development of a mathematical model and a heuristic approach where the routes are constructed and the service period is determined for the design of an internal milk-run material supply system. The material supply by this system occurs on a just-in-time basis from a central warehouse to several stations of an assembly line. The objective of the proposed mathematical model is the minimization of the total material handling and inventory holding cost. Besides, the proposed heuristic approach intends to construct routes based on an initial service period value and attempts to improve the solution by considering different period values. The most suitable solution is decided on the basis of the least total material handling and WIP/inventory holding cost. The application of the proposed heuristic in a TV assembly plant demonstrates the utility of it to the real practice.     

A mathematical programming approach to simultaneous unit-load and fleet-size optimisation in material handling systems design

This paper develops a model for simultaneously determining the optimal performance-based unit-load and fleet sizes for material handling vehicles serving work stations in a manufacturing system. The mathematical programming model maximises the number of units transported by the material handling vehicle during a given production cycle. The optimisation model simultaneously specifies the unit-load and fleet sizes, based on material transportation requirements and system characteristics.     

An new approach for the automatic analysis and control of material handling systems: integrated layout flow analysis (ILFA)

In the majority of small and medium sized enterprises (SEMs), the direct costs of material handling cannot be clearly measured. There are several reasons for this, including the large number of product types, complexity of their production cycle, and continuous change in markets. Therefore, production managers require flexible tools to create a suitable material handling system model which explicitly and rapidly calculates the indices required as these are traditionally neglected or laboriously approximated, (i.e., time and cost in material flow inside the factory, storage area requirements, and MH utilization percentage). This paper proposes an integrated approach to analyzing and controlling material handling operations in an industrial manufacturing plant from a “full quantitative” point of view. The model presented unites quite different fields of research into a unique methodology. This material handling model rapidly and automatically provides production managers with extensive and significant information. As a result, integrated layout flow analysis interrelates systematic layout planning with operational research algorithms and visual interactive simulation, using a complete software platform to implement them. This integrated layout flow analysis approach focuses on determining the space requirement for manufacturing department buffers, the transportation system requirements, the performance indices, and the time and cost of material flows spent in the layout and in MH traffic jams.     

飞机复合材料部件装配调度算法研究

以优化飞机复合材料部件装配顺序、缩短部件装配时间为目标,构建了复合材料部件装配调度模型,提出了一种启发式算法与禁忌搜索算法相结合的调度算法（HTA-AJSP）,并对其进行了优化,通过采用变邻域搜索和禁忌规则,很好地避免了算法搜索陷入局部最优。通过分析与实例验证,并与启发式算法和局部搜索算法进行比较,所提出的算法在产品装配调度优化问题上取得了比较满意的效果,缩短了装配周期,提高了装配效率。     

飞机复合材料部件装配调度算法研究

以优化飞机复合材料部件装配顺序、缩短部件装配时间为目标,构建了复合材料部件装配调度模型,提出了一种启发式算法与禁忌搜索算法相结合的调度算法(HTA-AJSP),并对其进行了优化,通过采用变邻域搜索和禁忌规则,很好地避免了算法搜索陷入局部最优。通过分析与实例验证,并与启发式算法和局部搜索算法进行比较,所提出的算法在产品装配调度优化问题上取得了比较满意的效果,缩短了装配周期,提高了装配效率。     

CMS scheduling problem considering material handling and routing flexibility

Cell manufacturing as an application of group technology increases the flexibility and efficiency of the production. Cell scheduling problem, one of the subjects in cell manufacturing, has not been widely studied by researchers compared with other problems in cell manufacturing. In spite of great importance of material handling in cell scheduling, it has not been paid enough attention by researches. In this paper, a new mathematical model for cell scheduling problem considering material handling time and routing flexibility is proposed. The proposed model belongs to the mixed-integer nonlinear programs (MINLP). A linearization procedure is proposed to convert the MINLP to an integer program (IP) in order to develop more powerful optimization tools. Furthermore, a simulated annealing-based heuristic is developed to solve the large-size problems.     

AGV schedule integrated with production in flexible manufacturing systems

Flexible manufacturing systems (FMS) comprise, automated machine tools, automated material handling, and automated storage and automated retrieval systems (AS/RS) as essential components. Effective sequencing and scheduling of the material handling systems (MHS) can have a major impact on the productivity of the manufacturing system. The material handling cannot be neglected while scheduling the production tasks. It is necessary to take into account the interaction between machines, material handling systems and computer. In this context, this paper attempts to link the operation of automated guided vehicles (AGV) with the production schedule and suggests a heuristic algorithm that employs vehicle dispatching rules (vdr) for conflict resolution. The vdrs considered in this paper are: shortest operation time (SPT), longest operation time (LPT), longest travel time (LTT) and shortest travel time (STT). The performance of the vdrs in the proposed heuristic is compared with makespan criteria. The results show that the STT provides the best solutions compared to other vdrs.     

装载机结构件装配线价值流分析与改善研究

基于工程机械行业装载机生产商S公司车间的实际生产情况,对其一结构件分装线进行分析,绘制了当前状态的价值流图。根据此图,找出分装线所存在的制约生产的主要问题,并结合工业工程和精益生产的方法改进装配工艺路线,优化生产布局,绘制了未来状态的价值流图。通过这些改善,缩短了产品生产周期,提高了生产效率,减少了物料搬运距离,给公司带来了良好的经济效益。     

多品种跨批量企业混合布局方式下的精益配送模型研究

多品种跨批量企业生产具有产品品种繁多、工艺复杂、产量多变等特点,缺乏拉动式准时生产的条件,在生产过程中容易存在半成品大量积压、产品生产周期过长等问题。针对这一问题,介绍一种不同于拉动式生产的工位物料的准时配送方法,利用混合布局方式,结合几个精益配送技术模块,提出了多品种跨批量企业的精益生产物料配送模型,使生产时的原材料和半成品在工位间高效流转,缩短产品生产周期,提高生产效率。     

Investigation of self-excited combustion instabilities in two different combustion systems

The objective of this paper is to characterize dynamic pressure traces measured at self-excited combustion instabilities occurring in two combustion systems of different hardware. One system is a model lean premixed gas turbine combustor and the other a fullscale bipropellant liquid rocket thrust chamber. It is commonly observed in both systems that low frequency waves at around 300Hz are first excited at the onset of combustion instabilities and after a short duration, the instability mode becomes coupled to the resonant acoustic modes of the combustion chamber, the first longitudinal mode for the lean premixed combustor and the first tangential mode for the rocket thrust chamber. Low frequency waves seem to get excited at first since flame shows the higher heat release response on the lower frequency perturbations with the smaller phase differences between heat release and pressure fluctuations. Nonlinear time series analysis of pressure traces reveals that even stable combustion might have chaotic behavior with the positive maximum Lyapunov exponent. Also, pressure fluctuations under combustion instabilities reach a limit cycle or quasi-periodic oscillations at the very similar run conditions, which manifest that a self-excited high frequency instability has strong nonlinear characteristics.     

Simultaneous scheduling of machines and vehicles in an FMS environment with alternative routing

Scheduling of flexible manufacturing systems is a well-known NP-hard problem which is very complex, due to additional considerations like material handling, alternative routing, and alternative machines. Improvement in the performance of a flexible manufacturing system can be expected by efficient utilization of its resources, by proper integration and synchronization of their scheduling. Differential evolution is a powerful tool which proved itself as a better alternative for solving optimization problems like scheduling. In this paper, the authors addressed simultaneous scheduling of both machines and material handling system with alternative machines for the makespan minimization objective. The authors proposed a machine selection heuristic and a vehicle assignment heuristic which are incorporated in the differential evolution approach to assign the tasks, to appropriate machine and vehicle, and to minimize cycle time.     

管子加工车间物料搬运系统的优化设计

为了改善船舶企业管子加工车间的物料搬运系统,加大物料搬运能力,降低生产物流成本,提高生产效率,缩短船舶制造的生产周期,以CQ企业管子加工车间为背景,通过现场勘查和定量分析企业管子加工车间搬运现状,结合生产材料的特性和生产设施的布置,使用IE（industrial engineering）现场管理、定置管理、看板管理、6S管理等技术,将系统中人、机、物料和方法重新整合,使物料集装单元化,改善了物料搬运路线,减少了物料搬运路程,设计出专用的物料柜和托盘架,高效、简单、精益化的适合船舶制造企业管子加工车间的物料搬运方案。     

基于斯坦克尔伯格博弈的入厂物流利益协调问题

为探讨入厂物流的利益协调问题,提出了由一个制造商和两个零部件供应商组成的两阶供应链.以零部件供应商库存成本和制造商运输成本最小化为目标,以博弈论为基础,建立了由制造商为主方,零部件供应商为从方的两阶斯坦科尔伯格主从博弈模型.制造商采取共同订货期为基础订货和循环取货的方式,并通过相应激励来诱使供应商参与合作.该供应链协调策略实现了两阶供应链库存一配送的联合优化.通过求解斯坦克尔伯格博弈模型,得出了最优的共同订货期.订货期倍数和激励奖金的数值解.最后给出了算法和仿真分析.仿真分析讨论了相关参数变化对制造商成本、零部件供应商成本和系统总成本的影响.     

A constructive heuristic for the integrated scheduling of machines and multiple-load material handling equipment in job shops

This paper extends the traditional job shop scheduling problem (JSP) by incorporating the routing and scheduling decisions of the material handling equipment. It provides a generic definition and a mixed integer linear programming model for the problem considering the case of heterogeneous multiple-load material handling equipment. A constructive heuristic is developed for solving the problem. This heuristic is based on the well-known Giffler and Thompson’s algorithm for the JSP with modifications that account for the routing decisions of the material handling equipment and their effect on the start times of the manufacturing operations. Different dispatching rules are integrated into the heuristic, and experiments are conducted to study their effect on the makespan along with the determination of the computational time requirements of the developed heuristic.     

基于价值流图的车载面板车间优化

价值流图是一种实施精益生产的工具,但是因价值流图不能详细描述生产系统的动态行为,导致其在精益生产应用方面存在局限性,通过结合仿真技术能够克服价值流图的静态局限性.针对D公司车载面板车间,首先运用价值流图识别车间存在的问题,并制定改善设计方案;接着,建立改善后的车间仿真模型,并以基本存储定量在制品控制策略(Base St...     

Optimal production policy for a manufacturing system with volume flexibility in a supply chain under lumpy demand

A batch production system with volume flexibility in a supply chain where a manufacturer procures raw materials and/or component parts from multiple suppliers in a lot and processes them into a single product, is considered in this research. First of all, a decision-making model is developed for an optimal production rate selection in the volume-flexibility production system, where a single type of finished products is delivered periodically in fixed quantities within a fixed interval of time. In this model, the production rate is perceived as a decision variable and unit production cost becomes a function of production rate. This model takes into account not only inventory costs of raw materials and finished goods, but production costs as well. Then, a pragmatic computation approach is presented to solve the proposed model for special unit-production-cost functions. It is used to determine an optimal production rate, and thus to decide an optimal ordering policy for procurement of raw materials from suppliers and an optimal manufacturing batch size. Some observations are made for optimal production rate analysis. Finally, a numerical study is conducted to illustrate the solution and a set of data with ten problems is tested and compared.     

A Petri net-based heuristic for simple assembly line balancing problem of type 2

In this paper, a Petri net-based heuristic is presented to solve simple assembly line balancing problem type-II (SALBP-2). Petri net is a mathematical and graphical tool to model and analyze for discrete event systems. SALBP-2 minimizes cycle time for given number of workstations. The presented heuristic determines available tasks and assign task to current workstation by using reachability analysis, one of the main properties of Petri nets, and token movement. Solution of SALBP-2 is implemented by iteratively solving the problem for several trial cycle time. If the cycle time is infeasible for given number of workstations, the heuristic increases the cycle time by a value until finding a feasible solution. To improve the solution, a binary search procedure is implemented between the first feasible solution and the last infeasible solution. Three versions of the heuristic are developed by integrating with forward, backward, and bidirectional procedures. All of them are coded in MATLAB, and their efficiencies are tested on benchmark datasets with 302 instances. Also a comparison study is made with a direct procedure and five heuristics based on differential evolution algorithm. Test and comparison results show that the proposed heuristic obtains good results for SALBP-2. Its performance is superior especially in large assembly lines.     

Learning curve constraint cell automaton model for the lean production of CFRP airframe components

A new model is proposed for the lean production of carbon fiber reinforced plastic (CFRP) airframes. Our method improves the production rate by determining the ideal human-capital balance and inventory density on the factory line. The proposed model is derived as a two-step process: First, an analytical solution for the learning rate shift with a human-capital ratio is obtained by merging the Wright learning curve model into the Cobb-Douglas production function. Second, the solution is factored by an asymmetric simple exclusion process (ASEP) cell automaton model to assess whether the inventory density negates the theoretical learning effect. Recent moves toward lean production mean that aerospace CFRPs have a limited shelf life, minimizing buffer periods under metastable and stable production in the time discrete ASEP model. The shift from metastable to stable changes the production rate. Combined with the fact that ASEP is known to drastically reduce throughput if the production steps are not harmonized, the shipment probability p at each step becomes less than 1. Therefore, the human learning effect, which can alter the shipment rate, must be controlled so that p=1 at each production step. This paper describes the analytical aspects of the apparent learning rate to determine adequate values for the human and capital resources, and thus harmonize the learning rates of the production steps. The analytical model shows that factory planning dominates the production rate of CFRP aerospace components. The model is applied to Boeing 787 production data, and it is found that a reduction in inventory density could improve the apparent delivery rate up to the maximum of the human potential.     

Fractional cell formation in group technology using modified ART1 neural networks

Group technology (GT) is a manufacturing philosophy that attempts to reduce production cost by reducing the material handling and transportation cost. The GT cell formation by any known algorithm/heuristics results in much intercell movement known as exceptional elements. In such cases, fractional cell formation using reminder cells can be adopted successfully to minimize the number of exceptional elements. The fractional cell formation problem is solved using modified adaptive resonance theory1 network (ART1). The input to the modified ART1 is machine-part incidence matrix comprising of the binary digits 0 and 1. This method is applied to the known benchmarked problems found in the literature and it is found to be equal or superior to other algorithms in terms of minimizing the number of the exceptional elements. The relative merits of using this method with respect to other known algorithms/heuristics in terms of computational speed and consistency are presented.