A Decision-Information-Synchronisation perspective on the performance of FMS

The performance of a Flexible Manufacturing System (FMS) largely depends on how the control system can control the flow of entities in the system. The control system takes control decisions based on the information provided as an input to the decision-making process. Therefore, it is important that the decision-making process and information systems operate in a synchronised manner with respect to the FMS characteristics. This can also be referred to as a Decision-Information-Synchronisation (DIS) operating zone implemented in the control system. To study the DIS in the present research, three types of visibility for decision-makers in FMS shop-floor control have been identified: (1) no local visibility, (2) physical local visibility and (3) physical and information local visibility of decision-maker/operator. These alternative visibilities and automation levels of decision and information system provide the hybrid environments of FMSs control. The current paper presents an approach to identify the DIS operating zone of FMS with suitable visibility of decision-maker and automation level. Simulation results show that under non-real-time control (low automation level in decision and information system) with physical local visibility, the FMS system performs comparable with the real-time control (high automation level in decision and information system) when routing flexibility levels are presented. Under the current global competitive environment, this study helps industrial managers determine a suitable level of visibility and automation in planning an FMS control system in order to obtain the desired performance at the lower cost.     

The effect of routing flexibility on a flexible system of integrated manufacturing

Flexible manufacturing systems (FMSs) have gained consideration due to their ability to produce customised and an increasing variety of products with shorter life cycles. A considerable amount of research has been done on manufacturing flexibility from different angles. There are many different types of manufacturing flexibility being reported in the literature, and routing flexibility is one of them. The paper focuses on the study of routing flexibility in a flexible system of integrated manufacturing (FSIM) from the view of real-time control strategies. However, flexibility incurs cost hence a judicious decision is required for implementing the right level of flexibility under a different operating environment. The paper studies the impact of routing flexibility and control strategies on the performance of FSIM. The application of discrete event simulation and Taguchi's method is applied to study the various factors contributing to FSIM performance and identifies the vital parameters for improving performance. Furthermore, the most significant factor is determined by using the analysis of variance (ANOVA). The result shows that increasing routing flexibility cannot be treated as a key role in system improvement. It is also found that there is the influence of control strategies on the performance of FSIM. Finally, it is observed that, the impact on the system performance due to the system load condition is the largest, and that of the number of pallets is the smallest.     

柔性制造系统检测监控系统的研究

根据柔性制造系统的实际需要，研制了一个ＦＭＳ运行状态检测监控系统，介绍了该系统的功能与结构，论述了系统与ＦＭＳ的集成方法，讨论了系统的工作流程及对ＦＭＳ故障的处理策略。     

FMS统一建模技术与方法

针对ＦＭＳ的组成结构及控制特点，提出了一种层次递阶的统一建模方法。以面向对象建模技术和方法为主线，通过消息传递驱动机制使各层递阶模型有机集成为统一的整体，并与实际系统中各个层次及其关系相对应，从而准确，方便地描术字ＦＭＳ的规划设计、调度控制、运行及仿真等各个过程。     

Using data continualization and expansion to improve small data set learning accuracy for early flexible manufacturing system (FMS) scheduling

Knowledge derived from limited data gathered in the early manufacturing stages is usually too fragile for a flexible manufacturing system (FMS). Unfortunately, production decisions have to be made quickly in a competitive environment. In a previous study, a strategy using continuous data and domain external expansion methods under a known data domain range was proposed to solve the so-called small data set learning problem in FMS. The present paper goes further in seeking a quantitative method to determine the range of domain external expansion under unknown domain bounds. The research considers the data bias phenomenon that often occurs in small data sets and provides a method for its adjustment. Beyond this, the study also compares the learning results among three types of membership functions (Bell, Trapezoid, Triangular) for data fuzzification. The results show that the proposed approach can advance the learning accuracy of a broad range of applications.     

A review of manufacturing flexibility: systematising the concept

The present work is an attempt to contribute to the conceptual systematisation of the manufacturing flexibility types by synthesising the vast literature available after a systematic review. We classified the papers in two perspectives (hierarchical and strategic), and engaged in a systematic process of standardisation of the definitions and names of various flexibility types leading to a better understanding of them. This process allowed us to clearly show: (a) the existence of a broader consensus in the field than expected; (b) that problems are limited to concrete aspects related to the level of analysis or the scope of certain flexibility types; (c) the possibility of a theoretical integration between the two perspectives which would permit a standardisation of the names and definitions for the flexibility types which make up the manufacturing flexibility construct.     

A method for comparing flexibility performance for the lifecycle of manufacturing systems under capacity planning constraints

The objective of this work is to describe a method for comparing the flexibility performance of manufacturing systems, in an uncertain environment, under lifecycle considerations and capacity planning constraints. The manufacturing systems costs are estimated over a time horizon and for a large variety of possible market scenarios. In order for the lifecycle cost values to be comparable among different systems, their values are calculated with the use of a special purpose algorithm. Statistical analysis of the estimated cost values is then employed for assessing the flexibility of each manufacturing system. The method is applied in an industrial case for checking, also from a flexibility point of view, the investment on a production system, using real life industrial data.     

Managing demand variability using requisite variety for improved workflow and operational performance: the role of manufacturing flexibility

In this study, we use the law of requisite variety to investigate the effect of manufacturing flexibility on workflow and operational performance. After developing a requisite variety construct using a parsimonious conceptualisation of manufacturing flexibility, we test our research model with data collected from US manufacturers. The results of the analysis using structural equation modelling support our hypotheses. Our study makes three important contributions. First, we provide a more complete understanding of manufacturing flexibility and its relationship to operational performance. By empirically testing our model, we develop support for manufacturing flexibility as a workflow regulator which provides an organisation with the necessary variety in its response-repertoire to effectively manage demand variability. Second, our analysis of our requisite variety construct allows us to better understand the complex relationship between manufacturing flexibility and efficiency. Our findings suggest that the trade-off between manufacturing flexibility and efficiency can be attenuated. Third, we provide evidence to show that manufacturing flexibility positively influences performance by increasing the speed of material flow and improving organisational efficiency.     

The influence of manufacturing flexibility on the interplay between exploration and exploitation: the effects of organisational learning and the environment

This paper analyses whether the firm can combine exploration and exploitation and seeks to determine whether implementing manufacturing flexibility will facilitate the development of either of these two terms or both simultaneously. This relationship was measured in 231 Spanish production firms. The results obtained show that: (1) firms develop exploration of new knowledge at the same time as they exploit their abilities; (2) manufacturing flexibility encourages the development of both exploration and exploitation; (3) this relationship is even more significant if we take into account dynamism of the environment and organisational learning.     

An ISM approach for modelling the enablers of flexible manufacturing system: the case for India

The volatile condition of today's market is forcing the manufacturing managers to adapt the flexible manufacturing systems (FMS) to meet the challenges imposed by international competition, ever changing customer demands, rapid delivery to market and advancement in technology. There are certain enablers, which help in the implementation of FMS or in the transition process from traditional manufacturing systems to FMS. The utmost need is to analyse the behaviour of these enablers for their effective utilization in the implementation of FMS. The main objective of this paper is to understand the mutual interaction of these enablers and identify the ‘driving enablers’ (i.e. which influence the other enablers) and the ‘dependent enablers’ (i.e. which are influenced by others). In the present work, these enablers have been identified through the literature, their ranking is done by a questionnaire-based survey and interpretive structural modelling (ISM) approach has been utilized in analysing their mutual interaction. An ISM model has been prepared to identify some key enablers and their managerial implications in the implementation of FMS.     

高级Petri网及FMS的动态建模和仿真

给出了一种柔性制造系统模型，它能模仿和跟踪车间中散件调度计划的执行过程。模型由一类新的高级Ｐｅｔｒｉ网组成，它定义了着色令牌，时化变迁和谓词变迁，抽象了物理对象的主要属性和它们间的基本关联。通过数据库描述令牌属性，规则库描述变迁，构成了一种结构紧凑，信息丰富，可反映多个工作进程的高级Ｐｅｔｒｉ网模型。     

A simulation analysis of factors influencing the flexibility of cellular manufacturing

The performance of cellular manufacturing (CM) systems in a variable demand and flexible workforce environment has been examined using simulation modelling. Discrepancies between academicians and practitioners’ findings with respect to flexibility and uneven machine utilization in CM systems are discussed. The views of two parties were incorporated in simulation models to rectify the existing discrepancies. While the results of this study confirm the previous findings of academicians regarding the deterioration of the performance of CM in a variable product mix situation, it appears that those results may be significantly influenced by considering a flexible workforce. The simulation results show that the practice of using flexible crossed-trained operators can improve the flexibility of CM in dealing with an unstable demand and can reduce load imbalance inherent in machine dedication in manufacturing cells.     

Agent-based modelling of movement rules in DRC systems for volume flexibility: human factors and technical performance

This research applies agent-based modelling (ABM) to study volume flexibility in a dual resource constrained (DRC) assembly flow shop environment. The simulation experiment evaluated system and human effects of varying DRC system staffing levels according to design (i.e., workforce, distance and buffer capacity), sensitivity (i.e. coefficient of variation) and operating (i.e. when rule and where rule) factors. Results showed that the rule by which workers are assigned to workstations affects WIP and flow time performances more than production rates. Furthermore per-worker productivity was found to increase, compared to the fully staffed system, particularly where the downstream movement rule was applied. Using the downstream rule when changing stations after completing current tasks reduced flow time (?15%) and WIP (?10%). If another where rule is chosen then it may be preferable for workers to move only after completing all jobs in the station (decentralised rule). For utilisation rates and mean hourly switching of work (human effects), the model shows complex relationships depending on almost all evaluated factors. The novel ABM approach used here enabled the evaluation of emergent system behaviours and showed potential to help firms understand both human and performance effects of operational choices in efforts to achieve volume flexibility.     

Prioritising the types of manufacturing flexibility in an uncertain environment

Researchers have stressed that manufacturing system flexibility research requires a quantitative model allowing a manufacturing system to prioritize its flexibility dimension and promote the performance of the manufacturing system. A quantification model presented in the present research is demonstrated to assess the degree of environmental uncertainty and illustrates a method for delivering the requirement of flexibility improvement for the manufacturing system so that the company is able to prioritize the types of manufacturing flexibility which a manufacturing system requires in an uncertain environment. Quantitative approaches including quality function deployment (QFD), analytical hierarchy process (AHP), and grey relational analysis (GRA) have been employed to find a means for improving the flexibility of a manufacturing system to cope with environmental uncertainty. QFD is the focal approach for the deployment of the integrated structure of the research. AHP is applied to explore the relative weighted importance of environmental uncertainty factors, while GRA is used to find out the relationships between manufacturing flexibility and environmental uncertainty. A combination of these approaches reveals a useful tool for managers to prioritize the types of flexibility which a manufacturing system requires for coping with an uncertain environment. In particular, the present research studied the manufacturing flexibility requirements of a food company in Taiwan.     

Intelligent decision support system for the adaptive control of a flexible manufacturing system with machine and tool flexibility

This paper describes an intelligent decision support system (IDSS) for real time control of a flexible manufacturing system (FMS). The controller is capable of classifying symptoms in developing the control policies on FMSs with flexibility in operation assignment and scheduling of multi-purpose machining centres which have different tools with their own efficiency. The proposed system is implemented by coupling of rule-based IDSS, simulation block and centralised simulation optimiser for elicitation of shop floor control knowledge. This posteriori adaptive controller uses a new bilateral mechanism in simulation optimiser block for offline training of IDSS based on multi-performance criteria simulation optimisation. The proposed intelligent controller receives online information of the FMS current state and trigger appropriate control rule within real-time simulation data exchange. Finally the FMS intelligent controller is validated by a benchmark test problem. Application of this adaptive controller showed that it could be an effective approach for real time control of various flexible manufacturing systems.     

An impact of manufacturing flexibility and technological dimensions of manufacturing strategy on improving supply chain responsiveness: Business environment perspective

The main objective of this research is to investigate the impact of manufacturing flexibility and technological dimensions of manufacturing strategy on responsiveness in the supply chain. Based on the theoretical background of dynamic capability, this study also examines the role of the business environment on the relationship between manufacturing flexibility and supply chain responsiveness. 144 structured surveys were collected and the partial least squares of structural equation modelling approach were utilised for data analysis. The result establishes relationships among various dimensions of manufacturing flexibility. Although the technological dimensions in manufacturing strategy of such advanced manufacturing technology (AMT) and e-procurement do not have any direct impact on new product and market flexibility, they increase supply chain responsiveness, which helps to react quickly against supply chain disruptions. More importantly, the business environment has a moderating effect on the relationship between market flexibility and supply chain responsiveness.     

Manufacturing process analysis with support of workflow modelling and simulation

Process analysis is recognized as a major stage in business process reengineering that has developed over the last two decades. Manufacturing process analysis (MPA) is defined as performance analysis of the production process. A manufacturing process analysis framework is outlined with emphasis on linking a company's strategy to operational process. Two issues, namely process modelling and simulation based analysis, are investigated. A compound workflow model (CWM) is proposed to provide graphic presentation of the production process that can be easily understood. Also it can be used directly by simulation to study the impacts of scheduling policy and analyse the process performance. A two-stage simulation analysis method is provided to quantitatively and efficiently define cause-and-effect relations to identify drivers for improvement. The manufacturing environment, PSC (production planning, scheduling and control) factors and the process structure are three main concerns considered in the simulation. An example is discussed in the final part of the paper.     

A methodology for cutting-tool management through the integration of CAPP and scheduling

Tool management is an important element in the efficiency of flexible manufacturing systems. This paper improves manufacturing flexibility through integrated computer-aided process planning and scheduling with tool management. A new methodology for cutting-tool management is introduced, based on the use of alternative tools. In the methodology proposed, computer-aided process planning singles out all possible tool alternatives for each operation. The tool manager is designed to solve interferences between tool alternatives to make them compatible with scheduling. Interferences occur when the same tools are simultaneously needed in various machining operations. We propose a method to reduce tool alternatives. Thus, interferences disappear, and a collection of tool alternatives compatible with the scheduling of the system is obtained for machining operations. Tool management can use these sets of tools to plan tool changes that are necessary to face tool wear and to react to perturbations in the production system. To prove the response of our proposal, computational experiments are performed on randomly generated test problems.     

Isophote-based ruled surface approximation of free-form surfaces and its application in NC machining

This paper presents a method to approximate free-form surfaces using piecewise ruled surface and its application in five-axis NC machining. New concepts of isophote, iso-inclination curve and iso-inclination angle are introduced to facilitate the generation of the piecewise ruled surfaces. The resulting ruled surfaces are adaptive to the surface features, such as peaks and valleys. Adjusting the isoinclination angle controls the error of this approximation. The application of the isophote-based ruled surface approximation in five-axis NC machining is also studied. The tapered tools are suggested to cut the ruled surfaces. Methods for selecting appropriate tools and generating tool paths are presented. The present case studies show that the new approach may lead to the integration of rough, semi-finish and finish machining of free-form surfaces.     

Modelling maintenance effects on manufacturing equipment performance: results from simulation analysis

Equipment maintenance and system reliability are important factors affecting the organisation’s ability to provide quality and timely services to customer. While maintenance remains an important function to manufacturing, it is only recently that attempts have been made to quantify its impact on equipment performance. In this research, an approach of linking maintenance with equipment performance is developed using simulation modelling. The modelling approach involves defining probabilistic models and assumptions affecting system performance, such as: the probabilistic model for the initial failure rate/intensity of the equipment; the probabilistic model for the system deterioration and corresponding effect; the probabilistic model for the random times of corrective maintenance (CM) and preventive maintenance (PM) that takes into the account the types of maintenance plans/policies and the potential dependency between CM and PM times; and the probabilistic model for the random effects of CM and PM on the reliability of the equipment. Using a continuous manufacturing equipment, the model is used to analyse the impact of deterioration, failures and maintenance (policies, timing and efficiency) on equipment performance. It is shown that modelling the effect maintenance provides a basis of evaluating maintenance efforts with the potential application in performance evaluation and decision support while investigating opportunities for manufacturing equipment performance improvement.