Typical Manufacturing System Research Articles

Real-time rescheduling metaheuristic algorithms applied to FMS with routing flexibility

This paper presents the results of a simulation study of a typical flexible manufacturing system that consists of seven machining centres, a loading and an unloading area, and six different part types. Owing to the existence of identical machining centres, the part types have alternative routings (their number varies between two and eight). One of the objectives of this work is to show how the following metaheuristics: ant colony optimisation, genetic algorithms, simulated annealing, tabu search, particle swarm optimisation and electromagnetism-like method, are adapted for solving the alternative routing selection problem in real time in order to reduce the congestion in the system by selecting a routing for each part among its alternative routings. The other goal is to highlight the impact of the real-time rescheduling of parts contained in the loading station on system performances when these metaheuristics are applied. The simulation results jugged by the production rate, machines and material handling utilisation rate show that for an overloaded system, the real-time rescheduling outperforms the case without rescheduling, but it has a negative impact on the work in process.

A cost‐based selective maintenance decision‐making method for machining line

AbstractMachine line is a type of manufacturing system in which machines are connected in series or in parallel. It is significant to ensure the reliability as well as to reduce the total cost of maintenance and failure losses in the maintenance programs of such systems. Cost‐based selective maintenance decision‐making, which is the best method for a selected group of machines in machine line is presented under limited maintenance durations. Fault losses and maintenance costs of a single machine under different maintenance actions i.e. minimal repair, preventive maintenance and overhaul on the fault rate of the machine are calculated. An algorithm combining the heuristic rules and tabu search is proposed to solve the presented selective maintenance model. Finally, a case study on the maintenance decision‐making problem of a connecting rod machining line in the automobile engine workshop is presented to illustrate the applicability of the proposed method. The end result shows that the fault losses can be further reduced by the optimization of maintenance interval and maintenance duration. Copyright © 2010 John Wiley & Sons, Ltd.

Effects of routing flexibility, sequencing flexibility and scheduling decision rules on the performance of a flexible manufacturing system

This paper focuses on a simulation-based experimental study of the interaction among routing flexibility, sequencing flexibility and part sequencing rules in a typical flexible manufacturing system (FMS). Two scenarios are considered for experimentation. Three routing flexibility levels, five sequencing flexibility levels and four scheduling rules for part sequencing decision are considered for detailed investigation. The performance of the FMS is evaluated using various measures related to flow time and tardiness of parts. The simulation results are subjected to statistical analysis. The analysis of results reveals that deterioration in system performance can be minimized substantially by incorporating either routing flexibility or sequencing flexibility or both. However, the benefits of either of these flexibilities diminish at higher flexibility levels. Part sequencing rules such as earliest due date and earliest operation due date provide better performance for all the measures at higher flexibility levels.

Development of simulation-based metamodels for the analysis of routing flexibility, sequencing flexibility and scheduling decision rules on the performance of an FMS

This paper focuses on the development of simulation-based metamodels for analysing the effects of routing flexibility, sequencing flexibility and part sequencing rules (PSRs) on the performance of a typical flexible manufacturing system (FMS). Three routing flexibility levels, five sequencing flexibility levels and four scheduling rules for part sequencing decision are considered for detailed investigation. The performance of the FMS is evaluated using measures related to flow time and tardiness of parts. Multiple regression-based metamodels have been developed using the simulation results. The analysis of results reveals that deterioration in system performance can be minimised substantially by incorporating either routing flexibility or sequencing flexibility or both. However, the benefits of either of these flexibilities diminish at higher flexibility levels. When flexibility exists, PSRs, such as earliest due date and earliest operation due date, provide better performance for all the measures.

Evaluating the Effect of Part-mix and Routing Flexibility on FMS Performance

The flexibility in manufacturing environment is implemented to respond proactively and cost effectively towards dynamic production requirements. Previous literature has explored eight common types of flexibility in manufacturing. This paper presents a simulation study based on Part-mix and Routing Flexibility and their impact on system performance of a typical Flexible Manufacturing System (FMS). ARENA based computer simulation models have been developed to investigate the effect of flexibility on the performance under various control strategies (sequencing and dispatching rules). The performance measure used in this paper is make-span time. Unbalanced type job shop FMS consist of four CNC general purpose machining centers and one loading/ unloading station is considered for the illustration of simulation models. These demo simulation models are intended for deterministic environment, and the use of discrete event simulation approach is adopted to offer a focus on dynamic behavior of FMS operating under different manufacturing strategies and flexibility types. This simulation study, under dynamic environment, may be very useful for practitioners. Management can obtain better insight and guidelines for determining various decisions relating to process and operations improvement and investment in new facility.

Design and selection of facility layout using simulation and design of experiments

In the global industrial competition, layout design and planning is becoming more and more critical due to shorter product life cycles and highly dynamic demand conditions. In this context, traditional layouts such as product and process/functional layouts are considered inferior. Cellular layouts have been proposed as an alternative to these layouts but they need a complete reallocation of resources, which consumes time and money. Hence, it is necessary to verify the performance measures before the design and selection of a certain type of layout. In this context, this paper makes an attempt to study the suitability of a virtual cellular layout (VCL) along with an existing functional layout (FL) of an industry and a classical cellular layout (CL), if considered for implementation. A Genetic algorithm (GA) based intra-cell formation procedure is used in the cellular layout design. To identify the suitability of a particular layout in a given environment, a typical manufacturing system is modeled using the WITNESS 2006 simulation software. Design of experiments (DOE) is used to plan the simulation experiments. The performance of each of the three layouts is analyzed statistically by means of operational parameters such as machine utilization, throughput, average distance traveled by parts and average work-in-process. The results from the simulation experiments indicate that the performance of virtual cellular manufacturing falls between that of functional and cellular manufacturing. Also, we find that the performance of a virtual cellular layout is often relatively superior to that of a functional layout and marginally inferior to a cellular layout.

Simulation-based metamodels for the analysis of scheduling decisions in a flexible manufacturing system operating in a tool-sharing environment

This paper presents the salient aspects of developing simulation-based metamodels for scheduling a typical flexible manufacturing system (FMS) operating in a tool-sharing environment. A discrete-event simulation model of the FMS is developed for the purpose of experimentation. Seven scheduling rules from the literature are incorporated in the simulation model for part scheduling decision. The performance measures considered for analysis are mean flow time, mean tardiness, and percentage of tardy parts. Simulation experiments have been carried out for various scenarios arising out of the settings of the mean interarrival time of parts for processing in the system and due-date factor. The simulation results are used to develop regression-based metamodels. These metamodels have been subjected to systematic analysis. The metamodels are found to offer a good prediction of the performance of FMS within the domain of their definition.

Sequencing and scheduling of job and tool in a flexible manufacturing system using ant colony optimization algorithm

Many optimization problems from the manufacturing systems are very complex in nature and quite hard to solve by conventional optimization techniques. The theme of this paper is to generate an active schedules and optimal sequence of job and tool that can meet minimum makespan schedule for the flexible manufacturing system. It consists of similar work center which is capable of doing many operations. The tools are stored in a common tool magazine that shares with and serves for several work centers to reduce the cost of duplicating tools in each and every work center. This type of manufacturing system is used for a manufacturing environment in which tools are expensive. To achieve the objective, the jobs and tools are sequenced and scheduled. In this work, non-traditional optimization technique such as ant colony optimization (ACO) algorithm are proposed to derive near-optimal solutions which adopt the Extended Giffler and Thompson algorithm for active feasible schedule generation. In this paper, the proposed algorithm is used for solving number of problems taken from the literature. The results available for the various existing algorithms are compared with results obtained by the ACO algorithm. The analysis reveals that ACO algorithm provides better solution with reasonable computational time.

Study of Flexible Scheduling System of the Hull Job Shop Based on OOCPN

The hull job shop in a shipyard is a typical flexible manufacturing system (FMS), the flexibility and efficiency of which largely depends on the level of FMS scheduling. In this paper, the Object-Oriented Colored Petri Net (OOCPN) is used to build the FMS model for the hull job shop. A four-step modeling method of FMS has been developed to successfully simulate the scheduling of the hull job shop.

Performance Analysis of a Flexible Manufacturing System

A typical Flexible Manufacturing System (FMS) has been studied under Planning Design and Control (PDC) strategies. The chief objective is to test the impact of design strategy (routing flexibility) on system performance under planning strategy (alternate system load condition) with control strategies (sequencing and dispatching rules). A computer simulation model is developed to evaluate the effects of aforementioned strategies on the make-span time, which is taken as the system performance measure. Shortest Processing Time (SPT), Maximum Balance Processing Time (MBPT) are the sequencing rules for selecting the part from the input buffer whereas for machine selection the dispatching rules are Minimum Number of parts in the Queue (MINQ), and Minimum queue with Minimum Waiting Time of all parts in the Queue (MQMWT). In this paper, the same manufacturing system is modeled under four different system load conditions. These load conditions are Full Balanced Load (FBL), Balanced Machine Load and Unbalanced Processing Time (BMLUPT), Unbalanced Machine Load and Balanced Processing Time (UMLBPT) and Unbalanced Load (UBL) with respect to machine load and processing time. The result of the simulation shows that there is continuous reduction in make-span with increase in routing flexibility when both machine load and processing times are unbalanced i.e., under UBL system condition.

Facilitating ease of system reconfiguration through measures of manufacturing modularity

In recent years, many design approaches have been developed for automated manufacturing systems in the fields of reconfigurable manufacturing systems (RMSs), holonic manufacturing systems (HMSs), and multiagent systems (MASs). One of the principle reasons for these developments has been to enhance the reconfigurability of a manufacturing system, allowing it to adapt readily to changes over time. However, to date reconfigurability assessment has been limited. Hence the efficacy of these design approaches remains inconclusive. This paper is the second of two in this issue to address reconfigurability measurement. Specifically, ‘reconfiguration ease’ has often been qualitatively argued to depend on the system's modularity. For this purpose, this paper develops modularity measures in a three-step approach. Firstly, the nature of typical manufacturing system interfaces is discussed. Next, the qualitative understanding underlying existing modularity measures is distilled. Finally, these understandings are synthesized for a manufacturing system context. This approach forms the second of two pillars that together lay the foundation for an integrated reconfigurability measurement process described elsewhere.

Predicting performance measures for Markovian type of manufacturing systems with product failures

Optoelectronic products are typically assembled and tested in a flow shop environment with multiple processors at each stage. The first few stages are dedicated for assembly and the later stages are dedicated for calibration and testing. Whenever a product (or job) fails at a stage, it is routed back to one of the downstream stages or to the same stage (depending upon the nature of the failure). Consequently, the product could circulate several times between the current stage and the preceding stage(s) before moving to the next stage. Estimating the performance measures (such as WIP and flow time) of such manufacturing systems is not trivial. This paper presents analytical approximations to estimate the performance measures of a manufacturing system with multiple product classes, job circulations due to failures, and some resources being shared among different product classes. The analytical approximations were verified using simulation on several problem instances. The experimental study indicates that these approximations can be used by operations managers to estimate the performance measures of a manufacturing system with product failures.

A guide for project-based manufacturers and secrets for software buyers

Most systems have their heritage in the Material Requirements Planning (MRP) philosophy developed in the 1960s. This concept utilized computer power to calculate time-phased material requirements. It later evolved into MRPII promoted by APICS and Ollie Wight during the 1980s, and further evolved to the Enterprise Resource Planning (ERP) systems available today. The original premise of all of these systems is that material planning is the center of the universe. The typical manufacturing system was designed with an MRP process at the heart of the system. The emphasis of such systems is on standard bills and routings and standard costs. Companies in the ETO world have different requirements. Designing and building complex products to exact customer specifications frequently involves long lead times and heavy engineering content. To win business, you must provide accurate estimates and quotations to a demanding customer base. Unlike the majority of manufacturers, capital equipment manufacturers typically purchase material to a specific project or job. You need to do progress billing and collect actual costs to projects. Often, you will not receive payment for a project until it is installed and operating at a customer's site. So, cash management is of vital importance. And after the sale, you need to track warranty information and provide aftermarket services, including the sale of spare parts that may constitute a significant share of your company's business.

THE MODEL FOR THE MODIFIED MINIMAL REPAIR/REPLACEMENT PROBLEMS WITH NEW TYPES OF REPLACEMENT

ABSTRACT In this paper, we develop a modified minimal repair/replacement problem which is formulated as a Markov decision process. The operating cost is assumed to be a non-decreasing function of the system's age. A specific maintenance action for a manufacturing system considered here is whether to have a replacement, to minimal repair or to keep it operating. However, the replacement of an improved system is available, which was assumed identical in the literature. This new “improved” system could be different in its lifetime distribution or in its associated costs for repair or replacement. It is shown that a control limit policy, or in particular a (t, T) policy, is optimal over the space of all possible policies under the discounted cost criterion. A two-phase procedure is developed for the optimal (t, T) policy with two types of manufacturing system based on the total expected discounted cost.

Investigations and practices on green manufacturing in machining systems

A machining system is a typical manufacturing system. A green manufacturing function framework of machining systems is structured to describe the traits of input, output and control elements in the system. Based on the function framework, the green manufacturing problem framework of machining systems is presented. The green manufacturing problems in machining systems are classified into three classes and related series of subclass problems. The three classes of problems in the green manufacturing problem framework are the problems of the minimization of resource consumption, the minimization of environmental discharge, and the synthesized minimization of both of them. A series of investigations and practices on green manufacturing in machining system, performed by the authors for quite a long period, are introduced in brief, such as the optimizing system for raw material cutting, the matching system for energy-saving in machining, the design of highly efficient dry hobbing machine tools, the multi-objective decision-making model for green manufacturing in machining systems, and the decision-making supporting system for green manufacturing in machining processes.

Real-Time Manipulation of Alternative Routeings in Flexible Manufacturing Systems: A Simulation Study

This paper presents the results of a simulation study of a typical flexible manufacturing system (FMS) that has routeing flexibility. The objective is this study is to test the effectiveness of the dissimilarity maximisation method (DMM) for real-time FMS scheduling. DMM is an alternative process plan selection method developed for routeing selection in off-line FMS scheduling. An integrated framework that consists of a computer simulation model, which mimics a physical system, a C++ + module, and a linear program solver is used to evaluate the effects of various operational control rules on the system performance. The hypothetical FMS employed in this study consists of seven machining centres, a loading and an unloading area, and six different part types. Owing to the existence of identical machining centres in the system, the part types have alternative routeings. For selecting an incoming part and later routeing it to a machining centre for its next operation, three control rules, namely, first-in first-out/first available (FIFO/FA), equal probability loading (EPL), and dissimilarity maximisation method/first-in first-out (DMM/ FIFO) are used. In this study, DMM is 1. Used as a real-time decision-making tool to select routeings for the parts that are in the system. 2. Tested and benchmarked against FIFO/FA and EPL. The results show that DMM/FIFO outperforms FIFO/FA and EPL on system throughput. Other measures such as average waiting time, average transportation time, and percentage utilisation rates are also investigated to provide insights for the effectiveness of the DMM rule for real-time FMS control applications.

Modelling for agile manufacturing systems

To address the challenges of a rapidly changing manufacturing market, a new type of manufacturing system with characteristics of reconfigurability, reusability and scalability, an agile manufacturing system (AMS) has to be developed. Reconfigurability is an essential feature of AMS. Such a system can use basic building blocks, both hardware and software, which can be reconfigured quickly and reliably. A fundamental early step in the reconfiguring process for an agile manufacturing system is to develop a model that adequately describes the proposed system, in order to be able to study and evaluate the impact of the reconfiguring decision on the system performance, before its construction. Therefore, the rapid modelling and reusable modelling capabilities are demanded. In this paper, an Object & Knowledge-based Interval Timed Petri-Net (OKITPN) approach is proposed, which provides an object-oriented and modular method of modelling manufacturing activities. It includes knowledge, interval time, modular and communication attributes. The features of object-oriented modelling allow the AMS to be modelled with the properties of classes and objects, and make the concept of software IC possible for rapid modelling of complex AMSs. Once all of the Interval Timed Petri-Net (ITPN) objects are well defined the developers need to consider only the interfaces and operations relating to the ITPN objects. In order to demonstrate the capability of the proposed OKITPN, it has been used to model rapidly AMSs that are reconfigured according to requirements.

Rapid Manufacturing System by Sheet Steel Laminating Method.

This paper discusses a new concept of the rapid manufacturing system that produces steel products automatically from CAD data. This paper proposes a sheet steel laminating method as one of typical rapid manufacturing systems, and develops a prototype machine of the method. A steel sheet coated with U-alloy is also developed as a special material for the machine, which enables us to solder steels by a hot press easily. This prototype machine is examined by manufacturing some machinery elements. This paper discusses performances and problems of the rapid manufacturing system, and possibility of sheet steel laminating method.

Model‐driven, component‐based approach to reconfiguring manufacturing software systems

Current practice when specifying and developing manufacturing software leads to enterprise systems that are difficult to change. With the purpose of improving current practice a model‐driven, component‐based approach to engineering change capable manufacturing systems is described. Application of the approach is supported by a number of proof‐of‐concept system design and construction environments. Each environment organises the use of modelling tools that function to formally capture and apply the results of systems engineering activities carried out by members of project teams. In this way the development of multi‐perspective enterprise (enterprise: a group of organisations sharing a set of goals and objectives to offer products, services or both (ISO 14258)) models is enabled in a computer executable form and means are provided to reconfigure manufacturing systems by using the models to change the way that system components interoperate. Collectively the proof‐of‐concept environments have demonstrated a capability to engineer a variety of types of manufacturing system and by so doing implement a system structure that accommodates rather than inhibits subsequent change, even where that change is of an unforeseen nature.

Failure rate distributions for flexible manufacturing systems: An empirical study

To aid researchers in the simulation and testing of maintenance policies for complex, computer controlled technological equipment this paper presents a description of failure and repair rate characteristics as well as distribution data for a typical flexible manufacturing system (FMS) that is in use in a mid-western (USA) manufacturing plant. Separate data are included for mechanical, hydraulic, electrical, electronic, software and human failures as well as repairs. The data are also fit with appropriate theoretical distributions.