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Nowadays, batch wise processing industry operates on a very dynamic market. To a certain extent, batch production plants have the desired flexibility to respond to these dynamics as uncertainties in product demand or new ecological targets. However, because of this flexibility, the complexity of the management and manufacturing operation increases considerably. The management of the operation is so complex, that to guarantee the continuity of the plant on the longer term, well-structured information and clear decision-making focussed on continuous improvement are absolute requisites. In this paper, a decision support framework (DSF) will be discussed aimed at giving more insights in the connection between operational activities and objectives of the plant and supporting the continuous search for improvements in operational and managerial tasks in such a way that the continuity of the batch plant can be better guaranteed. The different parts of the framework are illustrated on the basis of a continuous case study in a paper plant. The DSF includes two models, a generic objective model and a generic activity model, that can easily be adapted to the specific situation in which they are used and that are very valuable to obtain a better overview of all relations among operational objectives and activities. Moreover, the management team is supported to select from the large set of operational objectives, the ones that can really contribute to a better overall performance of the plant. This method for selecting promising objectives is based on AHP (analytic hierarchy process). [ABSTRACT FROM AUTHOR]

Rigorous development of theory in operations management has been lacking. Although many theories have been proposed, they are often not developed in a format and depth that can be falsified, refined, or supported. This special issue includes three papers that illustrate rigorous development of theory for future testing using mathematical, simulation, or managerial approaches. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to investigate the dynamics of accumulation processes of strategic capabilities in manufacturing, i.e. cost, quality, delivery, and flexibility. By applying a dynamic view, concepts from the literature are tested and shortcomings are identified. Design/methodology/approach – The analysis was conducted with the help of an exploratory system dynamics model that represented a hierarchy of these accumulative capabilities. The exploratory model was parameterized with empirical data from a large international survey of manufacturing plants. Findings – The major finding of this paper is that results from a static analysis can be transferred into a dynamic model, which can be used to test allocation strategies of resources to strategic capabilities. Practical implications – The practical implications concern the distribution of managerial attention on the four capabilities and the consequences of different distributions. Originality/value – The value of this paper lies in the insights gained by the transformation of a verbal model into a quantified simulation model, and the learning resulting from simulation experiments. [ABSTRACT FROM AUTHOR]

Nowadays the lean philosophy's tool- and rule system has spread into the production- and service areas as well. This is because companies using the lean philosophy are able to reduce their wastes continuously, thus they can gain a significant competitive advantage. One of the most important tools of the lean philosophy is the SMED method that enables a reduction in the changeover time of manufacturing/production processes. The reduction of the changeover time has a role in changing numerous parameters of the manufacturing/production process, which can result in increased efficiency of the examined manufacturing/production processes. The algorithm of the SMED method has been determined but application of simulation investigational methods can be necessary in many cases for increased efficiency. The paper introduces the application possibilities of the simulation investigational methods in the SMED method, as well as the concept for an elaborated investigational method. [ABSTRACT FROM AUTHOR]

Since testing wide range of management decision in real-world production is absolutely impossible, discrete-event simulation has often been adopted to evaluate the manufacturing system performance. Performance of various layout alternatives can be studied using simulation. In this paper there are presented reasons to use simulation in order to evaluate manufacturing system performance. Paper presents a simulation approach to assessing the impact of management decision on a production process and the associated impact on costs and on potential gain. [ABSTRACT FROM AUTHOR]

The role of flexibility in manufacturing is becoming most important as the pressures due to variety of products are continuously increasing coupled with declining volumes and faster response to customers. This paper deals with implementation of manufacturing flexibility at the shop floor level of the industry under consideration. The main objective of this paper is to compare the performance of existing manufacturing system with that of flexibility based manufacturing system. To achieve the objectives simple demo simulation model of the existing and proposed manufacturing system is built and performance compared. Both these system are compared on the following performance measures i.e., total production and total production time. The introduction of flexibility causes a decrease in makespan time, with maximum reduction in the makespan time occurring when routing flexibility is increased from 0 to 1. Also total production of parts increases with the increase in the level of flexibility. [ABSTRACT FROM AUTHOR]

The characteristic of layered manufacturing is the incremental build-up which inevitably leads to the staircase effect. One method to reduce this effect is to optimise part orientation and to apply adaptive slicing procedures. Although layer thickness will be decreased in some regions, process efficiency can be kept to a reasonable level. This paper presents different approaches of adaptive slicing for laser-based applications in consideration of limited range of thickness variation to ensure the mechanical part properties. In contradiction to previous work, the number of applied layer thicknesses is limited due to the associated process parameters. In order to optimise the slicing process and to obtain the best results, this paper presents a practicable approach based on existing work to simulate adaptive slicing. To underline the potential of non-uniform slicing, illustrative examples will show possible improvements in the case of replacing the uniform slicing procedure. [ABSTRACT FROM AUTHOR]

Over the past quarter century, much effort has been devoted to the design and development of simulation modeling languages, and to methods for the development of simulation models themselves. Less effort, however, has been expended on the design of the experimental models upon which simulation studies are based. This paper describes a methodology for the determination of near optimal solutions considering experimental design and simulation modeling. Using this methodology, simulation scenarios are created and analyzed using an analysis of variance (ANOVA)-based experimental design. This paper also presents an application of this method in analyzing a manufacturing system design problem. [ABSTRACT FROM AUTHOR]

A manufactured home is completely built in a controlled factory environment. Despite a large share of the market, the manufactured housing industry has a long way to go towards streamlining its production process. The objective of this paper is to map the production process of a manufactured housing factory and to demonstrate via simulation how the process can be improved. The production process including assembly, feeder, and storage stations were mapped using data from several manufactured housing plants and in-depth case studies at two plants in northern Indiana. The case study plants were also used for collecting cycle-time data for developing the simulation model for the roofing process. Subsequently, four “what if” scenarios were conducted to illustrate potential improvements to the production process. The efforts presented in this paper are part of on-going research sponsored by the National Science Foundation under the Partnership for Advancement of Technology in Housing (PATH) initiative. [ABSTRACT FROM AUTHOR]

This paper provides an executable design framework for modelling and controlling holonic manufacturing processes and systems. This framework is based on reconfigurable manufacturing holonic modules. These holonic modules consist of holons represented using parameterised Petri Net modules. As the suggested modelling framework shares advantages of IEC 61499 and FCPN-std, it supports the design of complex holonic manufacturing processes/system and allows simulation and analysis under general manufacturing uncertainties. Self-organisation activity in a holonic manufacturing system is explained using an evolution concept. A holon's inner evolution is executed through cascading parameterised Petri Net modules. This evolution is used for capturing the dynamic characteristics of a manufacturing environment. Routeing and reconfiguration is fulfilled through configuration evolution. It is achieved using the suggested constraint-based fuzzy Q-learning algorithm. The provided framework and two evolution algorithms are considered an executable design framework for modelling and controlling holonic manufacturing system. [ABSTRACT FROM AUTHOR]

In the past two decades, simulating workpiece–fixture interactions has remarkably drawn the attention of academia. However, many aspects of the workpiece–fixture system, specifically workpiece–fixture contact condition, still enjoy research effort. For the efficient use of Automated Fixture Design (AFD) systems, verification of their outputs is required. This paper presents a workholding simulation approach that considers assessment of AFD system outputs regarding different workholding parameters. The effect of friction forces on workholding and part rigid body stability is considered. Besides, determining deformation and stress in the workpiece, locators and clamps are modelled and their elastic deformation and stress distribution are computed. A procedure based on the application of contact elements in finite-element method is developed to quantify the status of contact between the workholding elements and the workpiece. Clamping tightness is modelled and its effect on the workpiece–fixture system performance is quantified. The central component of the verification tool is the use of nonlinear finite-element analysis to model the frictional interactions in workpiece–fixture system. [ABSTRACT FROM AUTHOR]

A common manufacturing environment in many industries (such as the glass, steel, paper, costume jewelry, and textile industries) is a hybrid flow shop. This system has continuous-process machinery in the first stage of manufacturing and repetitive-batch equipment in the second. Little research has investigated this type of system. Scheduling managers of hybrid flow shops tend either to use existing job-shop rules or to devise their own rules. These approaches often are less than adequate for efficient scheduling. In this paper we extend the rule presented by Narasimhan and Panwalkar to include a general class of hybrid flow shops. This extension, called the generalized cumulative minimum-deviation (GCMD) rule, is compared under various operating conditions to three other sequencing rules: shortest processing time, longest processing time, and minimum deviation. The operating conditions are determined by the number of machines at both stages. The results of 7200 simulation runs demonstrate that the GCMD rule is better than the other rules in minimizing each of five chosen criteria. Thus, the GCMD rule can help managers to schedule hybrid flow shops efficiently to achieve various corporate objectives. [ABSTRACT FROM AUTHOR]

The notion of service times is of such fundamental importance in the analysis of queues that it has long been taken for granted. Intuitively, it is used to represent the time interval that a server is capable of completing a dispatched job. However, actual measurements of service times under simple queues in production lines have encountered practical difficulties, in spite of its seemingly deterministic nature. Previous studies have introduced concepts of effective process times to quantify service times. Besides notions of theoretical processing times, raw process times and queueing times, among others, are commonly used in various applications. Their existence causes confusion in the determination of service times and clarification of such terminologies is needed. A simple model is examined to quantify the various concepts and establish their interrelationships. This paper brings out new properties of effective process times with a dynamic dependence on utilization. Discrete event simulations are conducted to verify these properties and explain the phenomenon of indetermination of service times. Both theoretical prediction and simulation results show that unless the system is fully loaded, service time and effective process time are not equivalent and it cannot be measured directly from observations of effective process times. [ABSTRACT FROM AUTHOR]

Discrete event simulation (DES) has been widely applied to modelling and simulation of computer and engineering systems and is an active field of research that has now evolved from 2D to 3D discrete event simulation. This paper attempts to address several key issues in a successful implementation of DES models based on our own and the previous experiences of others. It describes the common basis, which forms the core for the application of modelling and simulation methodologies that are available to support manufacturing systems analysis, design and performance evaluation. Through a comprehensive literature survey, this paper summarises and compares the most widely used optimisation techniques for simulation of manufacturing systems; an overview of the recent and popular simulation languages and packages available for the modelling and simulation community and the classification of their utility for modelling and simulation of manufacturing systems is also given. Finally, this paper summarises and reports the latest development in the most exciting world wide web (www)-based simulation techniques that represent a future that may completely change the nature and future exploitation of modelling and simulation technology in industry. [ABSTRACT FROM AUTHOR]

Operation flexibility is one of the eight common types of flexibility that exist in flexible manufacturing systems. Dispatching rules are commonly used in loading the machines. This paper studies the effects of different levels of operation flexibility and various dispatching rules on the performance of a flexible manufacturing system. The system performance considered is mean flow time. Simulation results indicate that the mean flow time cannot be always improved by increasing the level of operation flexibility. Altering the dispatching rules seems to have a more significant effect on the mean flow time performance than changing the level of operation flexibility. [ABSTRACT FROM AUTHOR]

We present a two-phase approach to design and analysis of manufacturing cells based on simulated experimentation and response surface methodology using a general manufacturing-cell simulation model. The first phase involves factor-screening simulation experiments to identity design and operational factors that have a significant effect on cell performance as measured by a comprehensive annual cost function. In the second phase of experimentation, we construct simulation (response surface) metamodels to describe the relationship between the significant cell design and operational factors ( the controllable input parameters) and the resulting simulation-based estimate of expected annual cell cost (the output response). We use canonical and ridge analyses of the estimated response surface to estimate the levels of the quantitative input factors that minimize the cell's expected annual cost. We apply this methodology to an assembly cell for printed circuit hoards. Compared to be current cell operating policy. the simulation metamodel-based estimate of the optimum operating policy is predicted to yield average annual savings of approximately $425 000, which is a 20% reduction in annual cost. In a companion paper, we detail the structure and operation of the manufacturing-cell simulation model. [ABSTRACT FROM AUTHOR]

We present a general manufacturing-cell simulation model for evaluating the effects of world-class manufacturing practices on expected cell performance. The modular structure of the simulation provides the flexibility to analyze a wide variety of manufacturing cells. We formulate a comprehensive annualized cost function for evaluation and comparison of alternative cell configurations. A case study involving assembly of printed circuit hoards illustrates the potential benefits of using this tool for cell design and analysis. The simulation model is intended for use in a two-phase approach to cell design that is based on simulated experimentation and response surface analysis as detailed in a companion paper. [ABSTRACT FROM AUTHOR]

In this paper, a new control scheme is proposed for Phase-II monitoring of simple linear profiles in multistage processes. In this scheme, an approach based on the U transformation is first applied to remove the effect of the cascade property involved in multistage processes. Then, a single max-EWMA-3 control statistic is derived based on the adjusted parameter estimates for simultaneous monitoring of all the parameters of a simple linear profile in each stage. Not only is the proposed scheme able to detect both increasing and decreasing shifts but it also has the feature of identifying the out-of-control parameter responsible for the source of process shift. Using extensive simulation experiments, the performance of the proposed method is evaluated and is compared with the ones of some other available methods for both weak and strong autocorrelations. Moreover, the diagnostic performance of the proposed method is evaluated. The results show that the proposed scheme performs well and works better than the competing methods. The application of the proposed method is illustrated at the end using a numerical example. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, we study the effects of an imperfect production process on the optimal production cycle time. The system is assumed to deteriorate during the production process and produce some proportion of defective items. The optimal production cycle is derived, and is shown to be shorter than that of the classical Economic Manufacturing Quantity model. The analysis is extended to the case where the defective rate is a function of the set-up cost, for which the set-up cost level and the production cycle time are jointly optimized. Finally, we also consider the case where the deterioration process is dynamic in its nature, i.e., the proportion of defective items is not constant. Both linear, exponential, and multi-state deteriorating processes are studied. Numerical examples are provided to illustrate the derivation of the optimal production cycle time in these situations. [ABSTRACT FROM AUTHOR]

In the last decade, over two dozen simulation studies have focused on comparing cellular and functional layouts. The results reported by these studies vary widely, however. This remains true even when the key performance measure is flow time. These variations reflect the disparate manufacturing and operating environments, as well as differences in parts demands, set-up economies, overall loads and other factors. This work attempts to reduce the sources of variation due to different operating assumptions while retaining the variability associated with differences in part mix and demand characteristics. Instead of focusing on a single data source, this study uses a test bed of six problems extracted from the literature and ensures they share the same operational rules. The simulation results show that conversion to CMS can reduce flow times (relative to the job shop configuration) consistently across all data sets, provided the same operating rules and ranges for key parameter are used. We investigate the reduction in flow time while controlling for the key factors of set-up reduction, overall load on the system and batch size. We also assess the benefits of using transfer batches as a further factor in reducing flow time. Our overall conclusion is that set-up reductions in cells can overcome pooling losses, even under the conservative assumptions where batch size remains unchanged and the material transport times in the job shop are assumed to be negligible. [ABSTRACT FROM AUTHOR]

Two alternatives to the multivariate exponentially weighted moving average (EWMA) chart are considered. One of these alternatives is an arithmetic moving average control chart which is the arithmetic average of the sample means for the last k periods. The other alternative is a truncated version of the EWMA which truncates the EWMA after a fairly short period of time so that more emphasis is placed on the most current observation. Simulated average run length (ARL) results indicate that for some situations these alternatives charts outperform the multivariate EWMA chart. Some suggestions are made for designing charts to detect a specific shift and comparing the alternative charts. Some authors have noted that past in-control data may diminish the chart's ability to detect a shift in the process mean. To examine this, the scenario will be discussed when the process is in-control initially but goes out-of-control at some random time period. This is more like a realistic manufacturing setting, where the process is in-control initially, but after some time the process mean shifts to a new mean and in this paper it will be shown which control charts detect a shift faster using this scenario. [ABSTRACT FROM AUTHOR]

Learning curve theory has been an important consideration for capacity planning and bid preparation since the 1940's. Constraint theory is a relatively new approach to managing manufacturing systems. This paper examines the implications each of these theories has for the other. Several important relationships are identified using a deterministic simulation of a simple production line which is influenced by learning and the presence of a system constraint. The rate of improvement of several measures of system performance follows the learning rate, but because of the role played by the constraint, other measures of performance actually get worse. [ABSTRACT FROM AUTHOR]

Releasing mechanisms are the set of rules which determine when matured orders i.e. those confirmed orders for which materials and tools are available, are dispatched to the shop floor so that processing can commence. This paper presents a simulation in which three such mechanisms are compared with a scenario in which matured orders are automatically released. Two of the mechanisms assume that the set of jobs to be released is given and that capacity cannot be adjusted. In contrast, the third rule allows capacity to be adjusted both as new jobs enter the system and as they are released to the shop floor. The simulation study shows that the latter rule is the best releasing rule under delivery performance and workload measures, but is slightly worse under the workload balance measure. This high performance is achieved at a relatively low cost in terms of increased capacity. In comparison with a scenario in which mature orders are automatically released to the shop, the latter rule performs better under all criteria except the proportion of tardy orders. It is concluded that further research is needed to show whether order release mechanisms can improve all delivery criteria as well as workload criteria. [ABSTRACT FROM AUTHOR]

This research describes one example of how the failure to understand the relationships between the flexibility associated with all resources within an FMS can he critical to overall performance. The need for such understanding is clearly spelled out by Jaikumar (1986). This research illustrates that even in situations where the demands placed upon the system are very well defined, tooling resources, such as pallets., may constrain overall system flexibility and subsequent system performance. In this paper, we simulate the operational performance of an existing FMS designed to manufacture a relatively small set of agricultural equipment components (only eight part types) over a known planning horizon using general purpose pallets and dedicated pallets. The simulation model is run under experimental conditions that include levels of demand mix variability, number of each type pallet available to the system, and incremental loading time and scrap rate when general Purpose pallets arc used. In most cases, the results indicate a significant increase in system performance when using general purpose pallets. In general, while system performance decreases as the level of demand mix variability increases, relatively higher throughput is obtained using general purpose pallets except where the assumed incremental loading times and scrap rates associated with assembling the pallets arc highest. System performance also improves as additional pallets are made available. In addition, overall system investment is impacted as fewer general purpose pails are required to achieve a given level of performance compared to the use of dedicated pallets. [ABSTRACT FROM AUTHOR]

The design of assembly lines for mass production and, in particular, the task of assigning and balancing work elements between stations on an assembly line, has frequently relied Upon the assumption that the problem conditions defined at the balancing stage will eventually become the operating conditions throughout the life of the assembly line. In many assembly line operations. especially those involving mixed-model or multi-model production, the acceptance of this assumption of continuity of problem conditions can lead to the introduction of assembly line designs that subsequently prove inefficient under actual operational conditions. The case therefore arises for an approach capable of examining this likely variation between the estimated balancing conditions and actual operating conditions (i.e. an approach to assessing assembly line versatility). Furthermore, there would be a distinct benefit when the examination of line versatility is undertaken at the assembly line design stage. Within this paper a simulation model, part of an integrated balancing and evaluation system capable of achieving this task, is described. Use of the simulation software is demonstrated by examples drawn from a test programme of over 200 simulations and summary conclusions are drawn from use of this simulation approach. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to report. on research conducted to develop a simulation model which incorporates the basic MRP logic into the modelled production process. The objective of the modeling effort, is to provide information necessary for planning and controlling of the material and capacity requirements of a production process that includes stochastic processes. The modelling and analysis procedure exploits the fact that the structure of the production process can be logically modelled as a network flow process. The technique employed to facilitate the network modelling is Q-GERT (Graphical Evaluation and Review Technique) modelling and simulation language. A case application is presented to demonstrate a prototype model, followed by a report of the simulation results. The model is designed to provide answers and insights to the following questions: (I) how tong must each production centre operate to yield the specified quantities of finished products, (2) what is the expected lead time required to complete the production of finished products, (3) what. are the utilization rates for various processing stations, and/or percentage idle times due to lack of preprocess inventories, and (4) where do bottlenecks occur in the production process. as evidenced by large queues of materials or subassemblies prior to the machine centres. [ABSTRACT FROM AUTHOR]

Models for production smoothing generally assume that production can be adjusted to any desired level. However, there are industries where production must be carried out at given discrete levels, for example by the opening or closure of certain facilities or by the use of shift-working. The problem is to control the operation in a way that will minimize the cost of changes in the level of production. The method explored in this paper relies on inventory levels for control purposes to trigger a switch from one production level to another. Sample results from simulation runs are cited as examples. [ABSTRACT FROM AUTHOR]

This paper proposes a technique for estimating steady-state quantiles from discrete-event simulation models, with particular attention paid to cycle time quantiles of manufacturing systems. The technique is based on the Cornish-Fisher expansion, justified through an extensive empirical study, and is supported with mathematical analysis. It is shown that the technique provides precise and accurate estimates for the most commonly estimated quantiles with minimal data storage and low computational requirements. [ABSTRACT FROM AUTHOR]

A system for geometric and physical simulation of the ball-end milling process using solid modeling is presented in this paper. A commercially available geometric engine is used to represent the cutting edge, cutter and updated part. The ball-end mill cutter modeled in this study is an insert type ball-end mill and the cutting edge is generated by intersecting an inclined plane with the cutter ball nose. The contact face between cutter and updated part is determined from the solid model of the updated part and cutter solid model. To determine cutting edge engagement for each tool rotational step, the intersections between the cutting edge with boundary of the contact face are determined. The engaged portion of the cutting edge for each tool rotational step is divided into small differential oblique cutting edge segments. Friction, shear angles and shear stresses are identified from orthogonal cutting data base available in the open literature. For each tool rotational position, the cutting force components are calculated by summing up the differential cutting forces. The instantaneous dynamic chip thickness is computed by summing up the rigid chip thickness, the tool deflection and the undulations left from the previous tooth, and then the dynamic cutting forces are obtained. For calculating the ploughing forces, Wu's model is extended to the ball-end milling process [21]. The total forces, including the cutting and ploughing forces, are applied to the structural vibratory model of the system and the dynamic deflections at the tool tip are predicted. The developed system is verified experimentally for various up-hill and down-hill angles. [ABSTRACT FROM AUTHOR]

In this paper the impacts of two types of repetitive scheduling systems on the makespan in a two-stage hybrid flow shop, which consists of one machine in the first stage and multiple process lines in the second stage, are compared. First, we analyzed, through a simulation, how the makespan is affected by the setup frequency and sequencing rules for products under two types of scheduling systems: One is repetitive scheduling with only one batch per product family per scheduling cycle (basic cyclic scheduling system). The other is repetitive cyclic scheduling with various batches per product family per scheduling cycle (variable cyclic scheduling system). Second, we compared which scheduling system is superior under various manufacturing situations. The following points were noted. (1) The superior scheduling system can be shown by a two-dimensional diagram of the setup frequency and the imbalance in workload for processing among process lines in the second stage. (2) Variable cyclic scheduling is superior in comparison with basic cyclic scheduling when there is a large imbalance in the work- load to be processed among process lines in the second stage, or the workload in the second stage is larger than that in the first stage. The result of this research provides guidelines for selecting which scheduling system should be adopted. [ABSTRACT FROM AUTHOR]

In this paper, the design principles of a new knowledge-based on-line simulation (KBOLS) architecture for the purpose of integrating the supervisory decision making process with a shop floor control system is discussed. The requirements for implementing the KBOLS architecture in a computer integrated manufacturing environment are presented. The special features of the KBOLS architecture include a knowledge-based controller capable of interacting with the shop floor and a manufacturing simulator, a shared blackboard data structure for knowledge bases, and a learning module. The KBOLS architecture is implemented in a flexible manufacturing system for analyzing interruptions due to machine breakdowns and rush orders. [ABSTRACT FROM AUTHOR]

Numerous methodologies have been developed for the plant-wide control (PWC) of industrial processes. These methodologies can be classified into heuristics, optimization, mathematical, and mixed approaches. However, most of these methodologies do not involve the extensive usage of rigorous process simulators as part of the control system development. Also, in recent years, the focus has shifted toward the use of mixed approaches, which builds synergies between different techniques. As part of the continuing search for more effective PWC system design methods, an integrated methodology is proposed in this paper. This eight-level framework incorporates heuristics and optimization, together with the use of simulation throughout the procedure. The main intuitive feature of this framework is the identification of key controlled variables for optimal operation; this is achieved by detailed analysis of disturbances, computation of the new optimal set points by reoptimization, and cost breakdown analysis for throughput changes. Another important feature is the use of dynamic performance measures to aid in analyzing the effects of integration. This framework is then applied to the styrene monomer plant case study presented earlier [Vasudevan et al. Ind. Eng. Chem. Res.2009, 48, 10941–10961] to develop a viable control structure. The performance of the resulting control system is compared with the control system developed using the integrated framework of simulation and heuristics. While both the control structures are found to be stable and robust in the face of disturbances, the control structure developed in the present work performs significantly better, in terms of steady-state profit and the dynamic economic index based on deviation from the production target. [ABSTRACT FROM AUTHOR]

Abstract: Unexpected disturbances and local decisions almost always deteriorate the execution of manufacturing plans. Digital enterprise technologies are hard to use, due to the complexity of production and the frequently changing circumstances. One of the main goals of the research described in the paper is the automatic model building of the discrete-event simulation system, based on intelligent analysis of the huge amount of information incorporated in the production database. The developed solution supports shop-floor dispatching and shop-floor managers in making control decisions. [Copyright &y& Elsevier]

During a manufacturing operation, exceptions may occur dynamically and unpredictably. Their occurrence may lead to the degradation of system performance or, in the worst case scenario, may interrupt the production process. The research proposes a multi-agent architecture for the capacity reconfiguration problem in a reconfigurable manufacturing system (RMS). A policy to manage capacity exchange among manufacturing lines based on due date performance is proposed. The Multi-Agent architecture was built in a simulation environment developed in ARENA® package and it is compared with a dedicated manufacturing and flexible manufacturing systems. The simulations are conducted in several demand scenarios to test the approach in a static and dynamic context. The simulation environment developed can support the planner to decide among the different manufacturing systems by the evaluation of the manufacturing performance. The simulation results, in dynamic environment, showed that the proposed approach leads to similar performance to flexible manufacturing system. [ABSTRACT FROM AUTHOR]

The operation of complex production processes is one of the most important research and development problems in process engineering. A safety instrumented system (SIS) performs specified functions to achieve or maintain a safe state of the process when unacceptable or dangerous process conditions are detected. A logic solver is required to receive the sensor input signal(s), to make appropriate decisions based on the nature of the signal(s), and to change its outputs according to user-defined logic. The change of the logic solver output(s) results in the final element(s) taking action on the process (e.g., closing a valve) to bring it back to a safe state. Alarm management is a powerful tool to support the operators’ work to control the process in safe operating regions and to detect process malfunctions. Predictive alarm management (PAM) systems should be able not only to detect a dangerous situation early enough, but also to give advice to process operators which safety action (or safety element(s)) must be applied. The aim of this paper is to develop a novel methodology to support the operators how to make necessary adjustments in operating variables at the proper time. The essential of the proposed methodology is the simulation of the effect of safety elements over a prediction horizon. Since different manipulations have different time demand to avoid the evolution of the unsafe situation (safety time), the process operators should know which safety action(s) should be taken at a given time. For this purpose a method for model based predictive stability analysis has been worked out based on Lyapunov’s stability analysis of simulated state trajectories. The proposed algorithm can be applied to explore the stable and unstable operating regimes of a process (set of safe states), information that can be used for PAM. The developed methodology has been applied to two industrial benchmark problems related to the thermal runaway. [ABSTRACT FROM AUTHOR]

The work described in this article consists of the development of a simulation model in an Arena environment, based on a real case, and is aimed at a very specific class of production lines, with a four closed-loop network configuration. The purpose of the use of an Arena simulation environment was that of enabling the production engineer to evaluate the performance of the automobile assembly line, through the variation of different parameters, thus contributing to an improved specification, characterisation and definition of the most efficient control system. In this paper we analyze the influence of the speed of the intermediate buffers formed by conveyors in assembly line performance, which has still not been researched in specialist literature. In order to obtain the functions that describe the behaviour of the assembly system, the design of an experiments technique was used. [ABSTRACT FROM AUTHOR]

In Finite Element Analysis of the Roll Forming (RF) process of automotive component, there are two methods for numerical simulation. The first one is general analysis, and the second is a specific analysis. The general approach is a deeper investigation but takes a long time for simulation, while the specific approach uses many assumptions for RF, takes less computer time and can analyze many special processes quickly. This paper investigates many RF processes of automotive components by using both methods, in order to identify differences between them as well as build the foundation for using the combination of different methods in analyzing and designing RF process. A realistic application in analyzing and designing is developed and shows the good efficiency in comparison with the previous procedure. [ABSTRACT FROM AUTHOR]

Abstract: Manufacturers of machine tools face worldwide competition which is tightened by demands for total cost of ownership (TCO) contracts, requiring a guarantee of a certain availability of their products. This availability is naturally affected by wear of machine components. It depends on the use of the machine tool in daily operation and correlates with the occurring load spectrum. The real load spectrum, however, is widely unknown. When designing a machine tool, the future load application is estimated from the designer''s experience. The real loading from cutting operations and motion usually highly differs from these assumptions. Hence, multibody simulation in combination with controls and CNC simulation offers the possibility to investigate the realistic load spectra of several machine components when performing the simulated operation of a given CNC program. The load levels can be accounted for, and the overall wear time can be accumulated and allocated to wear regions on the components with respect to the stressing. Thus, the progress of component life consumption can be obtained by simulation, which is useful for the appropriate requirements towards the machine''s components at the point of the machine design. This paper will present a practical approach to the estimation of machine tool component life based on simulation. [Copyright &y& Elsevier]

A mathematical model is established based on a modified Reynolds equation in polar coordinates, and solved by the multi-grid method to demonstrate the performance of micro-texturing mechanical seal surface. Sample cases of cylinder-shaped, square-shaped and diamond-shaped micro-asperity are studied to show the performance of micro-texturing mechanical seals. The results show that geometry has a vital influence on the friction coefficient and leakage. Diamond-shaped micro-texturing asperities have better performance than the others. And the performance is sensitive to the area density than the micro-texturing depth. The numerical approach can be a useful engineering tool, analyzing and optimizing the performance of micro-texturing mechanical face seals. [ABSTRACT FROM AUTHOR]

Abstract: The development of future products requires designing, manufacturing, and testing components in a virtual environment before hardware parts are actually made. This paper presents a generalized process simulation and multi-constraint optimization strategy for five-axis grinding with cubic boron nitride (CBN) wheels to increase material removal rates while avoiding process problems such as damage to the machined surfaces and premature wheel failure. The wheel–workpiece engagement conditions under five-axis grinding are extracted from a CAM system by geometrically processing the NC program, the wheel geometry and the part geometry. The interpreted geometric contact data are used in combination with empirical grinding models to predict physical process parameters such as forces, power, heat flux, and temperature. These parameters are then used as the decision variables in a multi-constraint optimization to optimize process parameters such as workspeed to reduce cycle time. [Copyright &y& Elsevier]

Abstract: In this paper we analyze and evaluate the effects of some pre-defined process parameters on the performance of a manufacturing system. These parameters include two different plant layout types, namely functional layout (FL) and cellular manufacturing layout (CL), as well as scheduling rule, machine downtimes, batch sizes, and transporter (interstage transporters) capacities. First we employ simulation to evaluate the effects of these factors on the performance of the system and then conduct designed experiments to set the best levels for these factors. The performance evaluation function is defined in terms of the average flow time of all the part types through the manufacturing system. Arena 10.0 simulation software and SPSS 9.0 statistical package are used to measure the main effects and interactions between these factors. This work demonstrates that various manufacturing parameters should be considered jointly when designing or redesigning a facility because setting different levels for parameters can considerably affect the performance of a facility. [Copyright &y& Elsevier]

The introduction of new materials into industrial components can give benefits in terms of cost and performance. It may also allow faster or cheaper production methods. However, in order to maximise the benefits, work must be done to optimise the material for its required role and to configure the process for efficient production.In this paper, the main stages in a streamlined cast one-step forge manufacturing process are modelled. A 3D model is used to optimise the mould design and process parameters. This model can be adapted to cope with variations in material without the need to resort to trial-and-error prototyping. In this case, the use of an A514 alloy with the addition of an in situ formed TiB2 particulate is investigated. Constitutive data for the simulations is derived from a series of lab-scale experiments.The structure and performance relations are established for an automotive component and the combination of material optimisation and simulated processing steps are validated by the pilot scale production and testing of an automotive suspension control arm. [Copyright &y& Elsevier]

Describes a method for modelling a negotiation-production manufacturing system which is an abstraction of the behavior of make-to-order companies participating in business-to-business trading networks. Features and functions of the model; Use of Markov chains in modeling the negotiation-production system.

Rapid product/process realization and enterprise integration have been identified among the major imperatives for enabling the next generation manufacturing paradigm. This paper proposes a virtual factory modeling approach to support these imperatives. A virtual factory is defined as an integrated simulation model of major subsystems in a factory that considers the factory as a whole and provides an advanced decision support capability. It seeks to go beyond the typical modeling of one sub-system at a time, such as the manufacturing model, the business process model and/or the communication network model developed individually and in isolation. A basic virtual factory model of a semi-conductor backend factory has been developed for concept demonstration. Application examples are used to demonstrate the integration between business processes and manufacturing system performance. Future work will move further towards the development of the complete virtual factory and its industry applications. [ABSTRACT FROM AUTHOR]

In this paper an analytical approximation for the performance of non-homogenous asynchronous Flow Production Systems (FPSs) with finite buffers is presented. Generally distributed stochastic processing times as well as breakdowns and imperfect production are considered. The procedure explicitly accounts for simultaneous blocking and starving. The approximation is based on the decomposition of an M-station-line into M -- 1 two-station-lines which are analyzed with the help of a GI/G/ I /Nmax queueing model. Numerical comparisons with exact and simulation results for hypothetical as well as for real-life flow-lines indicate that the procedure provides accurate results. [ABSTRACT FROM AUTHOR]

Manufacturing process simulations typically execute on a single platform, and are language and operating system-specific. With the growth of agile enterprises, however, the need is emerging to perform manufacturing process simulations in a distributed fashion from remote locations. In addition, individual businesses are becoming more decentralized, with geographically dispersed manufacturing and design teams. For effective concurrent engineering, product and process design teams that are in different locations need direct access to simulation tools. In addition, small- and medium-sized businesses cannot afford high-end computers and software for computationally intensive process simulations. Hence, these businesses could greatly benefit from easy access to high-end systems located remotely. The World Wide Web provides an excellent medium for remote collaboration and computing. Manufacturing process simulations can be deployed over the World Wide Web for remote access to simulations. This paper discusses the different methods for integrating manufacturing process simulations with the Web. An implementation of a Web-based metalworking process simulation with defect prediction is also presented. © 1997 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]