Modelling and simulation of flexible manufacturing systems (FMS)

Designs of flexible manufacturing systems (FMS) must be inspected using model experiments based on appropriate simulation software (SS). Problems connected with the development of SS will be discussed. Morover, a special modelling and simulation system suitable for FMS will be presented.     

A concise review of flexible manufacturing systems and FMS literature

The widespread popularity of Flexible Manufacturing Systems (FMS) has resulted in a prolific bibliography of literature describing several frameworks for analysis, planning and control of this automated mode of production. In this paper we review literature and discuss both the major characteristics of FMS and the contemporary decision support systems that have emerged to address the planning and control problems inherent in FMS.     

Design and planning problems in flexible manufacturing systems: a critical review

This review paper describes the state-of-the-art research on flexible manufacturing systems (FMS) design and planning issues. The emphasis is on presenting research results coming out of the current FMS literature that help the FMS manager in setting up a highly efficient manufacturing system. In addition to that, it discusses relevant research contributions after 1986, that were not part of any of the previous survey papers on operations research models for FMSs. Also, applications of combinatorial optimization approaches to FMS planning problems are adequately exposed in the paper.     

Robots in flexible manufacturing systems

The use of computer controlled manufacturing systems incorporating robots and flexible control is of paramount interest today. A number of economists have noted that strength in high technology industries such as aircraft, missiles, communications, electronic and computers, in contrast to older industries, gives the economy of any country strong long-term growth prospects.During the past two decades, the concept of a flexible, programmable automation device, which has come to be known as an “industrial robot”, has become a reality. A variety of these automation modules have been developed, offering a wide range of capabilities and application possibilities. Robots currently help weld, cast, form, assemble, machine, transfer, inspect, load and unload parts into and out of a number of differing machines and processes.The first part of this paper analyzes the significance of FMS in industries today. The second part of the paper attempts to evaluate some of the areas of savings as a result of using robots.     

Technical investment planning of flexible manufacturing systems—The application of practice-oriented methods

Flexible manufacturing systems (FMS) exhibit a high degree of automation of the machining system and of the workpiece, and for the information flow systems. Therefore, these systems are amongst the most complex production installations and their technical investment planning must be undertaken with great care.This paper introduces a strategic planning procedure and describes auxiliary aids for the selection of the components and for structuring of the overall system. Computer programs for the selection of machine tools and for the simulation of the manufacturing process sequence are part of this procedure. The application of the methods is illustrated by means of several problem situations arising from industrial production companies; the examples show the practical usefulness of the developed auxiliary techniques. The planning accuracy possible by these methods reduces the investment risk associated with the use of these complex manufacturing systems.Also described is an integrated system for the technical investment planning of flexible manufacturing systems which comprises both existing methods and new auxiliary means for planning the machining systems and the technical/organizational overall concept.     

柔性制造系统Petri网模型中的两类特殊资源*

在一类S3PR网柔性制造系统Petri网模型N中,考察两类所处位置特殊的资源。这两类资源分别被定义为第一类和第二类位置特殊资源。随后,证明这些资源不会出现在S3PR网N的任何一个严格极小信标(strict minimal siphon,SMS)或者是基本信标之中,并且任何使用这些资源的操作库所也不会出现在N的任何一个SMS或基本信标之中。结论说明,在柔性制造系统中可能存在一些同系统死锁的发生没有关系的资源。最后,简要介绍这两类特殊资源的应用前景。     

Optimum loading for GT/MRP manufacturing systems

A hierarchical planning procedure to utilize the potential advantages of coexistence of Group Technology (GT) and Material Requirement Planning (MRP) systems is presented. In addition, a multi-period linear programming model is proposed to determine the minimum cost loading schedule of manufacturing cells used in batch production environment. The proposed model provides the optimum work force for each cell over the planning horizon.     

Tool-provisioning strategies for flexible manufacturing systems

The difficulties encountered in managing the tool flow in flexible manufacturing systems for the manufacture of prismatic parts indicate the requirement to handle operational issues such as tool assignment. The choice of operational strategy and its relationship to machine specification, work and tool loading, scheduling and specific mode of tool management may significantly enhance machine utilization and work throughput. In this paper, strategies are presented aimed at improving system efficiency and minimizing tooling costs by considering tool provision as work-orientated, where the tooling is changed to suit the production task, or tool-orientated, where resident tools dictate the work flow, or a combination of the two. This paper draws on evidence from current industrial practice and recent developments.     

Using scheduling in flexible manufacturing systems

In this paper the concept of recursive Allen temporal algebra is fully described, along with its relationship to the smart scheduler program and the concept of smart scheduling in general. Flexible manufacturing systems (FMS) are described, and their relationship with smart scheduling is explored. A case study that shows the utility of SSP in an FMS environment is presented in detail. Conclusions about the concept of smart scheduling are presented in closing.     

Improving performance in flexible manufacturing systems

The need for flexible manufacturing systems (FMSs) has become of utmost importance over the last years due to the fierce competition present in the manufacturing industry as well as the ever decreasing product life spans and the markets attempts to respond to customers’ changing needs. These systems allow us to react quickly to changes, however this flexibility costs both time and money. Given this fact, it would be desirable to reduce costs by testing potential implementations before using them.We will use a timed process algebra called BTC (for bounded true concurrency) to face up to this challenge. We have developed this algebra by extending CSP in order to consider the duration of actions and the context (resources) in which processes are executed. This new algebra is able to take into account that the resources in a system must be shared by all the processes. So, we can find two kinds of delays in the execution of a process: delays related to the synchronization of processes, and delays related to the allocation of resources.Once FMSs are specified by means of BTC, we will focus our attention on the performance of the system which will be variable depending on the number of available resources. For this, we have developed a performance algorithm and a tool which implements it.Three examples are used to show how an FMS can be specified and how the algorithm and the tool work, allowing us to obtain the best performance with the lowest cost.     

Path-clearing policies for flexible manufacturing systems

In practical manufacturing settings it is often possible to obtain, in real-time, information about the operation of several machines in a flexible manufacturing system (FMS) that can be quite useful in scheduling part flows. The authors introduce some scheduling policies that can effectively utilize such information and they provide sufficient conditions for the stability of two such policies     

A survey of flexible manufacturing systems

In this report, the different flexible manufacturing systems used for machining and assembling in the following countries are reviewed: the United States, Japan, the Federal Republic of Germany, the German Democratic Republic, Italy, Great Britain, Sweden, Norway, France, Czechoslovakia and Hungary.Three categories of systems discussed are (1) flexible modules and units, (2) flexible transfer lines, and (3) “unaligned” flexible systems. Within each category are several sub-groups, divided up mainly according to the conveyor system and operating mode. This classification shows the effective French position in this field.     

A STEP-based manufacturing information system to share flexible manufacturing resources data

The paper describes the design and implementation of a Manufacturing Information System as a solution to share and exchange manufacturing data. The Manufacturing Information System possesses relevant features for data sharing and exchanging, that are compliant to the standard ISO 10303, known as STEP¹. It is known that manufacturing planning and execution activities require data from machine-tools, robots, ASRSs², AGVs³ and, on the other hand, computer-based applications (CAM⁴, CAPP⁵ or PAC⁶) use proprietary formats to store flexible manufacturing resources data. The way the proprietary formats are built has lead to incompatibilities and interoperability problems among the applications. It is argued that by solving these problems a qualitative functional synergy will result during manufacturing planning and execution activities. The suggested solution is using a STEP-based information system, a server and a prototype client application. These three programs are implemented in Java classes to facilitate data sharing and exchanging of flexible manufacturing resources.This revised version was published in June 2005 with corrected page numbers.     

Tool allocation in flexible manufacturing systems with tool alternatives

In this paper, a heuristic approach for tool selection in flexible manufacturing systems (FMS) is presented. The proposed approach utilizes the ratio of tool life over tool size (L/S) for tool selection and allocation. The proposed method selects tool types with high L/S ratios by considering tool alternatives for the operations assigned to each machine. The performance of the method is demonstrated in sample problems as static examples, as well as in a simulation study for further analysis. This study also presents a survey of several approaches related to loading and tool allocation problems in FMS, highlights the importance of tooling, and discusses the practical aspects of tool-oriented decision-making. An extended framework, which expands on the L/S concept, is also presented.     

Flexible manufacturing system (FMS) scheduling using filtered beam search

This paper reports our effort to develop a knowledge based system for scheduling jobs in a flexible manufacturing system (FMS). We view FMS scheduling as a two-stage process: static scheduling, followed by real-time rescheduling if unanticipated events were to occur. This paper deals with the static scheduling stage. The system uses a frame-based knowledge representation scheme and a problem-solving strategy based on filtered beam search. Filtered beam search views a scheduling problem as a state space search and generates a good schedule quickly by controlling the amount of search required. Evaluation functions are used to decide which branches are the most promising. An important feature of this system, in our view, is the explicit manner in which environmental, procedural and structural knowledge, (stored in the knowledge base using a frame-based scheme) can be used to improve the quality of the generated schedule. The system has been implemented and tested using Common Lisp on a Macintosh system with a 3MB main memory and a 40MB hard disk. Computational experience with our system is reported.     

Strategies for planning and implementation of flexible fixturing systems in a computer integrated manufacturing environment

In general, for any manufacturing operation to be successful, parts must be located and held to remain in position and orientation when subjected to external forces during the manufacturing operations. The traditional approach to fixturing involves designing and manufacturing special-purpose fixtures. These fixtures are generally dedicated devices designed and manufactured for specific parts and manufacturing operations. Flexible fixturing technology involves employing a single fixturing system to hold workpieces of various shapes and sizes. Such systems have reached the embryonic stage of implementation into manufacturing environment. Therefore the integration of current and future flexible fixturing systems into the manufacturing processes becomes an important issue for future work in computer-integrated manufacturing (CIM) environment.

The approach to CIM is dependent on the functional model of the company. Therefore, the implementation of any sub-systems within it must be studied on an individual basis. However, in order to plan and implement new technologies, such as flexible fixturing systems, within CIM environment, certain requirements must be met and guidelines must be followed. The strategies for planning and implementation of flexible fixturing systems within the larger frame work of CIM environment are presented. Some guidelines for designing and developing the interconnection of the data bases are also discussed.