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Purpose - This paper aims to develop path-planning techniques that support a general selective disassembly planner in a virtual reality environment. Design/methodology/approach - The paper presents an automatic selective disassembly planning and two path-planning techniques that support it. The first one is based on single translations, while the second is based on the generation of a random search tree. The methods used have been adapted and modified from available robotic path-planning methods for their use in disassembly path planning. Findings - The paper finds that the proposed techniques are applicable to the automatic generation of disassembly sequences. Research limitations/implications - The paper provides an automatic tool that can be integrated in simulation software for the analysis and validation of disassembly operation. Practical implications - Maintenance operations have a great impact in the security and life expectancy of any product. This is especially true for some applications such as aerospace that must pass rigorous security checking procedures. Geometric reasoning and virtual reality can help in reducing costs and design time by moving testing from physical mock-ups to virtual ones. Originality/value - The paper shows the integration of path-planning techniques in automatic disassembly-planning methods. [ABSTRACT FROM AUTHOR]

Interactive assembly based on virtual reality offers users an opportunity to interact with a virtual prototyping rather than a physical one and to validate assembly performance of products in a realistic way. Such evaluations could be available very early in the product development process ahead of any physical prototyping. The reduction or elimination of physical prototyping needed for assembly performance validation can substantially shorten the product development cycle and reduce development cost. Although virtual reality technology provides users an intuitive and immersive 3D interactive interface, it tends to be inaccurate because humans have difficulty in performing precise positioning tasks. Therefore, it is necessary to implement effective motion manipulation for assembly operations so that users can perform precise positioning efficiently in virtual assembly systems. This paper presents a constrained behavior management approach that realizes assembly relationship recognition, constraint solution and constrained motion for interactive assembly in a virtual environment. A constrained behavior manager (CBM) has been developed and applied in virtual assembly systems. Test cases confirm that constrained behavior manipulation proposed in this paper not only increases the efficiency of assembly relationship recognition, but also facilitates assembly interaction in a virtual environment. [ABSTRACT FROM AUTHOR]

The performance parameters of the manufacturing tasks (PPMT) are considered as the key parameters in constructing virtual enterprises (VE). It is difficult to determine the optimal or near-optimal values of PPMT. In this paper, the optimisation process in VE is perceived as a bidirectional optimisation process which consists of the forward and reverse process. By analysing the process, a reverse optimisation model based on vector norm theory is proposed and the target function is defined as a formula of the sum of the weighting Euclidean distance between two PPMT vectors. The existence of optimisation solution for the problem is investigated. Then an adaptive genetic algorithm based on natural number encoding is developed to solve the problem. A practical example is implemented to verify the validity of the proposed model and approach. The discussed results show that the optimal or near-optimal PPMT is helpful for the candidate enterprises selection in the process of constructing a VE. [ABSTRACT FROM AUTHOR]

Virtual reality (VR) can be described as a four-dimensional (4-D) simulation of the real world, including the 3-D geometry space, 1-D time and the immersive or semi-immersive interaction interface. VR applications in mechanical-related research areas are becoming popular, e.g. virtual layout design, virtual prototyping, Internet-based virtual manufacturing, etc. However, research in VR applications is facing conflicting requirements for high rendering quality and near real-time interactivity. This paper represents an Internet-based virtual machining system that builds an integrated VR scene, which combines images and models, to overcome the above conflicts. This research is divided into three parts: first, image mosaics techniques are used lo implement an Internet-based virtual workshop, which is an image-based virtual scene. The method of obtaining original sequential images, the principle of image mosaics to realize automatic seamless stitching, and projection transformation matrices to reconstruct a closed inward-facing space are presented. Secondly, a model-based virtual milling machine has been constructed with three detailed approaches: a category-based dynamic graph structure to support collision detection, a relation-oriented collision detection method to improve the efficiency of collision detection, and a dynamic modelling method to model a dynamic workpiece object. Finally, an Internet-based virtual milling system, which is the integration of the image-based virtual workshop and the model-based virtual CNC machine, is constructed using the reposition method to achieve visual consistency of the virtual objects and images. This system, which includes an integrated scene, combines the advantages of image-based VR and model-based VR. Consequently, this system has both high rendering quality and good real-time interactivity. [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]

Resin infusion (RI) process has been widely used for manufacturing composite parts. The variation of preform thickness brings great difficulty to the three-dimensional simulation of the filling stage. To accurately simulate the preform thickness change and resin flow during resin infusion, precise preform compaction models and dynamically changing geometry models need to be adopted. At present, resin flow is usually considered as two-dimensional and simple compaction models are employed to simplify the simulation, which degrades the prediction accuracy seriously. In this paper, general equations to describe the resin flow in the changing thickness cavity are developed, and the viscoelastic model is adopted which can fully express the dynamic characteristics of the preform compaction. To avoid solving the coupled resin flow/preform deformation equations directly, the volume of fluid method and the dynamic mesh model are employed to implement the tracking of the flow front and updating of cavity geometry model. The resin storage and release induced by porosity variations are adjusted by a master-slave element method to ensure mass conservation. Two simulation examples are carried out to demonstrate the capability of the above approach. The applicability of the approach on arbitrary complex domains and sequential injection strategy is also verified. [ABSTRACT FROM AUTHOR]

A dynamic model of a flexible manufacturing system (FMS) is considered based on the information characteristics of system infrastructure. According to the physical architecture and working requirements, a software framework for FMS modelling and simulation is proposed to describe the parallel flow of different work-pieces in the shop. The model is based mainly on the concepts of both object-oriented programming and high-level Petri net methods. A material transportation protocol is designed to realize the respective processing of routine orders of work-pieces within the main resources of the FMS shop. Using a specially designed protocol, a fully automated job shop FMS can be achieved. An FMS simulation tool that can show the dynamic process of all the system resources during task execution is finally introduced. [ABSTRACT FROM AUTHOR]

During powder based additive manufacturing processes, a component is realized layer upon layer by the selective melting of powder layers with a laser or an electron beam. The density of the consolidated material, the minimal spatial resolution as well as the surface roughness of the resulting components are complex functions of the material and process parameters. So far, the interplay between these parameters is only partially understood.In this paper, the successive assembling in layers is investigated with a recently described 2D-lattice Boltzmann model, which considers individual powder particles. This numerical approach makes several physical phenomena accessible, which cannot be described in a standard continuum picture, e.g. the interplay between capillary effects, wetting conditions and the local stochastic powder configuration. In addition, the model takes into account the influence of the surface topology of the previous consolidated layer on the subsequent powder layer.The influence of the beam power, beam velocity and layer thickness on the formation and quality of simple walls is investigated. The simulation results are compared with experimental findings during selective electron beam melting. The comparison shows that our model, although 2D, is able to predict the main characteristics of the experimental observations. In addition, the numerical simulation elucidates the fundamental mechanisms responsible for the phenomena that are observed during selective beam melting. [ABSTRACT FROM AUTHOR]

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Layered manufacturing has emerged as a highly versatile process to produce complex parts compared with conventional manufacturing processes, which are either too costly to implement or just downright not possible. However, this relatively new manufacturing process is characterized by a few outstanding issues that have kept the process from being widely applied. One such issue is the reduced part accuracy caused by the primitive method of generating the layer contours. Current practice generates the layer contours by simply intersecting a set of parallel planes through the computer model of the design part. The volumetric geometry of each layer is then constructed by extruding the layer contour by the layer thickness in the part building direction. This practice often leads to distorted part geometry due to the unidirectional bias of the extruded layers. This paper proposes a novel scheme to correct the systematic part distortion of layered manufactured parts resulting from the improperly generated layer contours. A new layer contour generation method utilizing the sectional projected data of a point cloud representation of the part surface is introduced. The systematic part distortion is reduced by extruding the outer boundary of the projected point data into the layer volumetric geometry. The boundary contour construction algorithm is able to adapt to changing density of the point set in order to keep the captured level of detail consistent. Specifically devised case studies were carried out to validate the proposed method. [ABSTRACT FROM AUTHOR]

In recent years significant worldwide research effort has been directed towards the computer representation of manufacturing decision-making logic, especially in its application to process planning. This paper describes the concept of a machine planner, which can provide detailed machine-specific planning information to aid both in process-planning decision making and NC code generation. Machine planning decisions are made by integrating manufacturing data, constraints and methods with solid model information. The problem of planning for different machine-tool types is considered, while concentrating on the machining of prismatic parts on 3-axis vertical machining centres in its current software implementation. The use and structure of pre-defined. parametric, manufacturing features in solid models is discussed. [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]

In order to realize autonomous manufacturing systems in environments characterized by high dynamics and high complexity of task, it is necessary to improve the control system modelling and performance. This requires the use of better and reusable abstractions. In this paper, we explore the metamodel techniques as a foundation to the solution of this problem. The increasing popularity of model-driven approaches and a new generation of tools to support metamodel techniques are changing software engineering landscape, boosting the adoption of new methodologies for control application development. [ABSTRACT FROM AUTHOR]

Virtual reality (VR) is a very helpful and valuable work tool for the simulation of manufacturing systems. It can be used in both industrial and academic/researcher fields allowing the system's behaviour to be learnt and tested. VR provides a low-cost, secure and fast analysis tool. It also provides benefits, which can be reached with many different system configurations. The work presented in this paper reviews some of the most recent developments that have been made in this way and proposes a general methodology for the creation of virtual environments applicable to manufacturing systems. The application samples of this procedure are focused on flexible manufacturing systems (FMS), in which the economic and safety problems are heightened. [ABSTRACT FROM AUTHOR]

This paper compiles selected predictive analytical and numerical tools which can be used to model and understand the mechanisms of importance at different stages during and immediately after extrusion-based 3D printing of cementitious materials. The proposed toolbox covers different aspects of the process including mixing, material transportation, layer deposition, mechanical behavior of the fresh printed structure, and its early curing. Specifically, the paper provides basic analytical methods that should be helpful for an initial, first-order analysis of a given printing process. These methods deliver, in turn, a first estimation of some material requirements and process parameters. Limitations of these analytical methods are also discussed. Furthermore, the paper presents a review of advanced numerical tools that can be used to simulate the steps in the printing process accurately. It is shown that these tools can serve to describe complex behaviors, help in designing process parameters, or optimizing the rheological response, even though further developments are still needed to capture fully the attendant physical mechanisms. [ABSTRACT FROM AUTHOR]

To cope with large fluctuations in the demand of a commodity, it is necessary for the manufacturing system to have rapid reactive ability. This requirement may be secured by performance measurement. Although manufacturing companies have used information systems to manage performance, there has been the difficulty of capturing real-time data to depict real situations. The recent development and application of the Internet of Things (IoT) has enabled the resolution of this problem. In demonstration of the functionality of IoT, we developed an IoT-based performance model consistent with the ISA-95 and ISO-22400 standards, which define manufacturing processes and performance indicator formulas. The development comprised three steps: (1) Selection of the Key Performance Indicators of the Overall Equipment Effectiveness (OEE), and the development of an IoT-based production performance model, (2) Implementation of the IoT-based architecture and performance measurement process using Business Process Modelling and (3) Validation of the proposed model through virtual factory simulation. We investigated the effect of the IoT-workability on the OEE, based on the final results of the simulation, both for the planned and actual productions. The simulation results showed that the proposed model represented the timestamp data acquired by IoT and captured the entire production process, thus enabling the determination of real-time performance indicators. [ABSTRACT FROM PUBLISHER]

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]

The ultimate goal of future manufacturing is to design, test, and manufacture parts in a virtual environment before they are sent to the shop floor While Part I of this paper presents the modeling of process simulation in a virtual environment, this second part presents computationally efficient algorithms for optimal selection of depth of cut, width of cut, speed, and feed while considering process constraints and variation of the part geometry along the tool path. The objective function is selected as the material removal rate (MRR), and optimization of milling processes is based on user defined constraints, such as maximum tool deflection, torque/power demand, and chatter stability. The MRR is maximized by optimal selection of cutting speed, feed rate, depth, and width of cut. Two alternative optimization strategies are presented. Preprocess optimization provides allowable depth and width of cut during part programming at the computer aided manufacturing stage using chatter constraint, whereas the postprocess optimization tunes only feed rate and spindle speed of an existing part program to maximize productivity without violating torque, power and tool deflection limits. Optimized feed rates are filtered by considering machine tool axis limitations, and the algorithms are tested in machining a helicopter gear box cover. [ABSTRACT FROM AUTHOR]

Abstract: In a manufacturing system, we need to capture collaborative processes among its components in order to clearly define supporting functions of a system. However, pervasive process modeling techniques, including IDEF3, Petri Nets, and UML, are not sufficient for modeling collaborative processes. Therefore, we have developed a novel modeling method referred to as collaborative process modeling (CPM) to describe collaborative processes. CPM models can be transformed into marked graph models so that we can use the analysis power of Petri Nets. In this paper, we first briefly discuss these process modeling techniques. Then, we illustrate the CPM method and transformation rules with illustrative examples. CPM allows us to develop collaborative process models, understand and facilitate the realization of collaboration, and verify models before moving onto development. [Copyright &y& Elsevier]

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]

Commercially available flow sheet simulators cannot perform optimization runs with more than one criterion. To overcome this problem, the flow sheet simulator CHEMCAD is combined with an external optimization solver, and the Excel VBA client is used to arrange inter-process communications. The resulting tool for multi-criteria optimization in chemical process engineering is applied to two separation problems. First, a dividing-wall column is used as a theoretical example to test different starting points and different scalarization techniques. Second, a significant decrease in energy demand is achieved for a real continuous world-scale facility. [ABSTRACT FROM AUTHOR]

Any proposal for a perfect relocation of production lines and the subsequent operation of the production system is still subject to further change. They are caused by innovation of products on the market, qualitative and quantitative requirements of the customer etc. Resolving of material flows is actual term in present. It brings a lot of problems with layout of particular devices as elements of manufacturing process according to required and defined technology. In present time are suitable software tools for improving of transport, manipulation and storage systems. The simulation of these three systems relation is realized support CA systems to optimal whole technological processes. In this case this problem is solved by simulation software Witness used in Institute of Manufacturing Systems and Applied Mechanics of our faculty. [ABSTRACT FROM AUTHOR]

The efficacy of virtual reality (VR) as a design support technique is widely recognised by industries. However, the efficiency of the routine employment of VR into the product development process (PDP) still finds an obstacle in the poor integration of the tools employed. The use of VR still needs long and quite hard procedures to work effectively; the models have to be converted into a format that is compatible with VR systems and each task requires an effort to prepare the virtual environment or to post-process the results that depend on the complexity of the task. This work analyses some VR applications into the PDP and describes some ideas to effectively support the operator that prepares the virtual environment. These ideas have been tested by developing four software interfaces, able to create an easy data exchange link between VR and other design tools like CAD, CAE and computer aided control engineering (CACE). [ABSTRACT FROM AUTHOR]

Presents information on a study which examined the use of simulation tools in the design and development of manufacturing systems in Japanese manufacturing industries. Importance of the design of manufacturing systems; State of simulation research in the country; Simulation competence.