Solving facilities location problem in the presence of alternative processing routes using a genetic algorithm

Facilities location problem deals with the optimization of location of manufacturing facilities like machines, departments, etc. in the shop floor. This problem greatly affects performance of a manufacturing system. It is assumed in this paper that there are multiple products to be produced on several machines. Alternative processing routes are considered for each product and the problem is to determine the processing route of each product and the location of each machine to minimize the total distance traveled by the materials within the shop floor. This paper presents a mixed-integer non-linear mathematical programming formulation to find optimal solution of this problem. A technique is used to linearize the formulated non-linear model. However, due to the NP-hardness of this problem, even the linearized model cannot be optimally solved by the conventional mathematical programming methods in a reasonable time. Therefore, a genetic algorithm is proposed to solve the linearized model. The effectiveness of the GA approach is evaluated with numerical examples. The results show that the proposed GA is both effective and efficient in solving the attempted problem.     

高速列车复合材料地板振动性能分析

为分析不同复合材料高速列车地板减振性能的差异,对其进行力学性能测试,分别采用多层叠混合模型及单层模型计算复合结构材料的等效参数并验证.建立包含内装地板的高速列车车体有限元模型;基于实车线路测试结果,以车体底架振动加速度信号作为地板瞬态响应激励,计算复合地板材料结构的瞬态振动响应及振动传递率,得到不同复合材料地板的振动特性.研究结果表明：桦木芯材优于桤木芯材;外层面板厚度的增加使得地板的减振性能增强,但过大会导致减振性能下降;不锈钢面板比铝合金面板地板结构固有频率低且质量较大,不利于车体轻量化设计.     

Synthesis of waffle plates in the post buckled domain

Typical of many structural elements, plates retain a considerable amount of strength and stiffness in the post-buckled domain. Utilizing the latent strength and stiffness of the plate, this paper reports on the synthesis of metal and composite waffle plates under mechanical and thermal loads with weight as the objective function. The weight of the waffle plate is reduced as the out-of-plane displacement of a panel of the waffle plate is increased. Several examples under various mechanical and thermal loads are presented to illustrate the synthesis of waffle plates in the linear post-buckled domain.     

Manufacturing planning and predictive process model integration using software agents

Intelligent agents provide a means to integrate various manufacturing software applications. The agents are typically executed in a computer-based collaborative environment, referred to as a multi-agent system. The National Institute of Standards and Technology (NIST) has developed a prototype multi-agent system supporting the integration of manufacturing planning, predictive machining models, and manufacturing control. The agents within this platform have access to a knowledge base, a manufacturing resource database, a numerical control programming system, a mathematical equation solving system, and a computer-aided design system. Intelligence has been implemented within the agents in rules that are used for process planning, service selection, and job execution. The primary purposes for developing such a platform are to support the integration of predictive models, process planning, and shop floor machining activities and to demonstrate an integration framework to enable the use of machining process knowledge with higher-level manufacturing applications.     

Modular supervisory control for multi-floor manufacturing processes

Due to space availability limitations and high land costs, there is an increasing development of multi-floor manufacturing (MFM) systems in urban and industrial areas. The problem of coordination in a multi-floor manufacturing process, in the Ramadge Wonham framework, is introduced. The manufacturing chain of each floor and the elevator system are modeled in the form of finite deterministic automata. The models of the multi-floor manufacturing process are parametric with respect to the number of floors and the number of manufacturing machines on each floor. The coordination desired performance is formulated in the form of desired regular languages in analytic forms. The languages are realized by appropriate supervisors in the form of finite deterministic automata. The models of the supervisors are also parametric with respect to the number of floors and the number of manufacturing machines on each floor. The total control of the coordination of the multi-floor manufacturing process is accomplished via a modular supervisory control architecture. The complexity of the supervisors as well as the complexity of the total modular supervisory architecture are determined in analytic forms with respect to the number of floors and the number of manufacturing machines on each floor. The special case of a two floor manufacturing process is presented as an illustrative example.     

Optimum design of stiffened structures with constraint on the frequency in the presence of initial stresses

Structural optimization often leads to simultaneity of two or more failure modes. The interaction between failure modes must be included in the constraint set for a safe design. In this paper, stiffened cylindrical panels and waffle plates are designed with constraints on static instabilities, natural frequencies and initially stressed vibration frequencies. The interaction between instability and the natural frequency of the structure is considered. The erosion of structural safety when instability and free vibrations are assumed to be independent of each other is shown. Numerical examples are included to illustrate the interaction phenomenon.     

A macroelement for waffle slab analysis

Behaviour of a waffle slab under transverse loading is investigated through a series of three-dimensional finite element analyses, and modal analysis of a deformed waffle slab cell. “Macroelement” concept is introduced, taking an advantage of the repetitive nature of waffle slab cells and the fact that only few deformation modes participate significantly in sustaining transverse loads. Less significant deformation modes are removed with little consequence by appropriate kinematic constraints. The result is a macroelement cell with fewer degrees-of-freedom.The macroelement is shown to retain all the dominant deformation modes of a waffle slab cell. Results from tested example show good performance of the proposed macroelement with considerable amounts of computer time and storage saved.     

Effective selection and allocation of material handling equipment for stochastic production material demand problems using genetic algorithm

This paper addresses the stochastic production demand problem in a manufacturing company. The objective of this research is to minimize the waiting time of production workstations and reduce stochastic production material problems through coordinating pickup and delivery orders in a warehouse. RFID technology is adopted to visualize the actual status of operations in production and warehouse environments. A mathematical model is developed to address this problem and a meta-heuristic algorithm using genetic algorithm (GA) is also developed to improve performance. Computational experiments are undertaken to examine the performance of the algorithm when dealing with congestion in cases of heavy and normal demand for production material. The overall result shows that the algorithm efficiently minimizes the total makespan of the production shop floor.     

高速列车浮式地板振动响应有限元分析

针对采用试验方法开发高速列车浮式地板耗时耗力,且试验规模小,不能反映整车的振动效果的问题,基于有限元法进行高速列车振动响应分析.对三明治夹芯理论、蜂窝板理论和等效板理论进行比较,确定采用等效板理论数值模拟某浮式地板中的蜂窝板;利用橡胶材料的超弹性理论拟合橡胶材料参数;建立完整模型模拟实际工况下浮式地板的振动响应,得到浮式地板的隔振效果.结果表明此浮式地板的隔振效果约为90%,满足设计要求.     

Model for establishing theoretical targets at the shop floor level in specialty chemicals manufacturing organizations

The work in this paper introduces a model that focuses on three issues at the shop floor of specialty chemicals manufacturing. The three issues are cycle time of the process, production yield, and economic production capacity. This is in order to define theoretical performance targets that enable the process to operate with the highest possible output and minimum waste in terms of time, material, and resource. The basis for the proposed model is that the theoretical targets would be referenced alongside the actual process and results of will be compared to define performance gaps and identify improvement opportunities. Results from work in this paper will support benchmarking process, performance measurement, and also, the applicability of lean manufacturing on the shop floor of specialty chemical plants. This work has also demonstrated the proposed model as new effective tool to measure and benchmark performance of process plants.     

A manufacturing XML schema definition and its application to a data management system on the shop floor

Digitization for sharing knowledge on the shop floor in the machinery industry has been given much attention recently. To help engineers use digitization practically and efficiently, this paper proposes a method based on manufacturing case data that has a direct relation to manufacturing operations. The data are represented in XML schema, as it can be easily applied to Web-based systems on the shop floor. The definitions were made for eight manufacturing methods including machining and welding. The derived definitions consist of four divisions of metadata, work-piece, process and evaluation. Three divisions except for the “process” division are common to the manufacturing methods. The average number of elements for a manufacturing method is about 200. The represented schema is also used to convey knowledge such as operation standards and manufacturing troubleshooting on the shop floor. Using the definitions, a data management system is developed. It is a Web-based Q&A system, in which the engineers specify the manufacturing case data mainly by selecting from the candidates. Then, the system fills in the blank portions and/or shows messages to help complete the case data. The proposed method is evaluated through practical scenarios of arc welding and machining.     

Task-driven e-manufacturing resource configurable model

Manufacturing resource configuration (MRC) plays a very important role in an e-Manufacturing system. Higher requirements for optimal configuration under online resource visibility and traceability have led to two main challenges. One is that more features of manufacturing tasks affecting the optimization results should be taken into consideration when establishing the MRC mathematical model for a manufacturing cell. The other is that manufacturing information should be given equal attention as MRC to realize real-time visibility and traceability of the resulting manufacturing cells. This paper presents a comprehensive mathematical model which considers more practical features of manufacturing tasks (e.g. batch volume and alternative processing routes) for manufacturing cell formation. This model adopts a fuzzy clustering method to group the manufacturing tasks and machines. Moreover, it is enabled by a smart equipment model to realize the configurable model of real-time manufacturing information and corresponding visualization and tracing methods. A case study is given to demonstrate the proposed models and methods.     

Dynamic planning model for determining cutting parameters using neural networks in feature-based process planning

Although feature-based computer-aided process planning plays a vital role in automating and integrating design and manufacturing for efficient production, its off-line properties prohibit the shop floor controllers from rapidly coping with unexpected production errors. The objective of the paper is to suggest a neural network-based dynamic planning model, by which the shop floor controllers determine cutting parameters in real-time based on shop floor status. At off-line is the dynamic planning model constructed as a neural network form, and then embedded into each removal feature. The dynamic planning model will be executed by the shop floor controllers to determine the cutting parameters. A prototype system is constructed to validate whether the dynamic planning model is capable of determining dynamically and efficiently the cutting parameters for a particular set of shop operating factors. Owing to the dynamic planning model, the shop floor controller will increase flexibility and robustness by rapidly and adaptively determining the cutting parameters in unexpected errors occurring.     

A cost benefit analysis for industry 4.0 in a job shop environment using a mixed integer linear programming model

As the manufacturing industry is approaching implementation of the 4th industrial revolution, changes will be required in terms of scheduling, production planning and control as well as cost-accounting departments. Industry 4.0 promotes decentralized production and hence, cost models are required to capture costs of products and jobs within the production network considering the utilized manufacturing system paradigm A new mathematical cost model is proposed for assessing the cost-benefit analysis of introducing Industry 4.0 elements to the manufacturing facility, specifically, integrating and connecting external suppliers as strategic partners and establishing an infrastructure for communicating information between the manufacturing company and its strategic suppliers. The mathematical model takes into consideration the bi-directional relationship between hourly rates and total hours assigned to workcentres/activities in a certain production period. A case study, from a multinational machine builder, is developed and solved using the proposed model. Results suggest that though an additional cost is required to establish infrastructure to connect suppliers, the responsiveness and agility achieved resulting from uncertainty outweighs the additional cost.     

考虑同质设备不同加工能力的模块化制造单元资源配置优化

针对传统制造单元易出现在制品的积压、加工效率低下的问题,提出一种模块化制造单元资源配置模型及算法。按照模块化思想进行制造单元划分,为了保证单元内部均衡,工作站内可配置若干个同类设备。考虑到同类设备之间的加工效率不同,建立以总加工成本最小及制造单元内与单元间的均衡为目标的数学模型,应用模拟植物生长算法进行求解。最后通过算例验证了模型与算法的有效性。     

Virtual machine tools and virtual machining—A technological review

Virtual manufacturing systems provide a useful means for products to be manufactured ‘right the first time’ without the need of physical testing on the shop floor. Earlier research was mostly on developing a virtual manufacturing environment. Over the years, simple graphical prediction and simulation gave way to complex multi-science predictions. Virtual systems such as Virtual Machine Tool, Virtual Machining, Virtual Assembly, Virtual Tooling and Virtual Prototype have been developed to support virtual manufacturing. Different systems and approaches have different targeted applications. This paper aims to provide a comprehensive review of existing virtual systems. Their focuses and approaches (i.e. virtual reality, Web-based techniques, mathematical modelling, hardware interactions and STEP-NC-based methodologies) are discussed in detail. To better understand the systems, we have categorized them into different groups according to their application domains. Discussions and concluding remarks are given based on the review.     

Evolving CBR and data segmentation by SOM for flow time prediction in semiconductor manufacturing factory

Flow time of semiconductor manufacturing factory is highly related to the shop floor status; however, the processes are highly complicated and involve more than 100 production steps. Therefore, a simulation model with the production process of a real wafer fab located in Hsin-Chu Science-based Park of Taiwan is built for further studying of the relationship between the flow time and the various input variables. In this research, a hybrid approach by combining Self-Organizing Map (SOM) and Case-Based Reasoning (CBR) for flow time prediction in semiconductor manufacturing factory is developed. And Genetic Algorithm (GA) is applied to fine-tune the weights of features in the CBR model. The flow time and related shop floor status are collected and fed into the SOM for clustering. Then, a corresponding SGA-CBR method is selected and applied for flow time prediction. Finally, using the simulated data, the effectiveness of the proposed method (SGA-CBR) is shown by comparing with other approaches.     

Digital vibration threshold testing and ergonomic stressors in automobile manufacturing workers: a cross-sectional assessment

Upper extremity musculoskeletal disorders (UEMSDs) comprise a large proportion of work-related illnesses in the USA. Physical risk factors including manual force and segmental vibration have been associated with UEMSDs. Reduced sensitivity to vibration in the fingertips (a function of nerve integrity) has been found in those exposed to segmental vibration, to hand force, and in office workers. The objective of this study was to determine whether an association exists between digital vibration thresholds (VTs) and exposure to ergonomic stressors in automobile manufacturing. Interviews and physical examinations were conducted in a cross-sectional survey of workers (n = 1174). In multivariable robust regression modelling, associations with workers' estimates of ergonomic stressors stratified on tool use were determined. VTs were separately associated with hand force, vibration as felt through the floor (whole body vibration), and with an index of multiple exposures in both tool users and non-tool users. Additional associations with contact stress and awkward upper extremity postures were found in tool users. Segmental vibration was not associated with VTs. Further epidemiologic and laboratory studies are needed to confirm the associations found. The association with self-reported whole body vibration exposure suggests a possible sympathetic nervous system effect, which remains to be explored.     

A process-driven computing model for reconfigurable semiconductor manufacturing

Reconfigurability is essential for semiconductor manufacturing systems to remain competitive. Reconfigurable systems avoid costly modifications required to change and adapt to changes in product, production and services. A fully automated, collaborative, and integrated while reconfigurable manufacturing system proves cost-effective in the long term and is a promising strategy for the semiconductor manufacturing industry. However, there is a lack of computing models to facilitate the design and development of control and management systems in a truly reconfigurable manner. This paper presents an innovative computing model for reconfigurable systems and controlled manufacturing processes while allowing for the integration of modern technologies to facilitate reconfiguration, such as radio frequency identification (RFID) and reconfigurable field programmable gate array (FPGA). Shop floor manufacturing activities are modeled as processes from a business perspective. A process-driven formal method that builds on prior research on virtual production lines is proposed for the formation of a reconfigurable cross-facility manufacturing system. The trajectory of the controlled manufacturing systems is optimized for on-demand production services. Reconfigurable process controllers are introduced in support of the essential system reconfigurability of future semiconductor manufacturing systems. Implementation of this approach is also presented.     

避免死锁调度的数学建模与求解

通过引入"资源分配函数"的概念建立了以最短加工时间为目标函数的制造系统避 免死锁调度的数学模型,给出了该模型在两进程情况的最优解算法和多进程情况的可行解 算法.