Intelligent workstation controller for computer-integrated manufacturing: Problems and models

A shop floor control system (SFCS), which is the most important component of any production control system, ff has a direct e ect on the productivity of a tool room. The SFCS presented in this paper aims at streamlining various tool room activities, such as process planning, operations scheduling, loading, progress monitoring, and performance monitoring. The system discussed in this paper is characterized by simplicity and is user friendly. Basic information, consisting of three types of information (order details, process details, and part details), is input through interactive dialogue sessions. On-line updating of the process information is carried out, again through interactive dialogue sessions. The basic input to the system along with the on-line updating enables a number of useful and important reports and documents to be generated ff by the system for e ective control of the shop floor. The reports generated include operations scheduling, process sheet, part list, ffi job card, load pending report, e ciency report, etc. This SFCS is developed for a medium sized tool room in an automotive company and its successful implemention reduced paperwork and improved resource management and has resulted in productivity. It can be said that this system offers a first venture into computer integrated manufacturing (CIM) for a tool room.

The high cost and long development cycle of shop floor control systems and the lack of true system integration capabilities are identified as one of the most challenging obstacles in deploying e-Manufacturing systems. Overcoming these obstacles is essential for manufacturers to execute a make-to-order business model in order to stay competitive and remain profitable in the future. We propose a formal method to generate the desired control trajectories and provide true integration mechanisms for shop floor control systems. Using the proposed architecture can result in the development of an e-Manufacturing system capable of achieving a substantial reduction of both the high cost and long development cycle currently required to engineer shop floor control systems. By taking advantage of both the linear growth of the complexity function in a structured adaptive supervisory control model and the information-centric characteristics of a virtual production line in a manufacturing execution system, a formal model, which we call an extended structured adaptive supervisory control, for a discrete manufacturing system is introduced. A shop floor control system based on the extended structured adaptive supervisory control model is built for an industrial testbed system. The shop floor control system is fully tested and evaluated.

Implementing an Information Control System for Manufacturing

New Product Developments

In the previous chapter we presented an information technology reference architecture for FC and PAC. We now describe some Information Technology tools and standards, currently available and under development, which we believe may be important in realizing successful implementations of FC and PAC. Our primary objective in this chapter is to examine our information technology reference architecture for shop floor control systems, and associate with it specific hardware and software tools. We briefly review the most important information technology tools and standards, and give examples of how these tools can be applied in real-life shop floor control systems. Furthermore, we stress the importance of portability, flexibility and inter-operability for shop floor control systems, attributes which we believe are vitally important in a multi-vendor computing environment. The structure of this chapter is as follows: 1 We present an initial overview of information technology, highlighting the importance of flexibility, inter-operability and portability of IT systems. A general computing model is then introduced, and this contains four essential elements required to realize an information technology implementation of shop floor control. These elements are communication systems, data management systems, processing systems and user-interface systems. 2 The main body of the chapter describes the relevant state-of-the-art technologies of the four elements included in the general computing model. At the conclusion of each section, a synthesis of what we believe are the most suitable technologies is presented, in the form a shop floor control model for each particular computing element. Thus, we also present a communication systems model, a data management model, a processing model and an user-interface model for the implementation of FC and PAC systems. 3 Finally, we focus our attention on the emerging object-oriented technology, which holds the promise of highly portable, flexible and interoperable solutions within the domain of shop floor control.

The integration of process and production planning plays an important role in the commitment of Computer Integrated Manufacture (CIM) missions. Various research approaches have been proposed in the last decade. Due to the complexity involved in both process planning and production scheduling, this integration task remains far from being resolved. Based on reviewing previous research, this paper has developed a taxonomy for the integrated planning problem. The most urgent task at this stage is to develop an architectural model which can be further implemented in real world manufacturing systems. An object-oriented modeling technique is therefore employed to build the integration model, so that maximum flexibility and extensibility of the integration system can be obtained for different applications.

Production-Monitoring Integration in Planning and Control of FMS

This paper examines the role that both the planning and shop floor control systems play in the operation and performance of a dual resource constrained (DRC) job shop. Using causal analysis, the results show an effective planning system, as it accounts for the largest gain in shop performance. Generating and releasing smoothed schedules (work loads) allows the use of simplified shop floor control procedures such as Order Review/Release (ORR), job dispatching and labour assignment rules without adversely affecting performance. This study uses the results to resolve the current paradox surrounding ORR systems and shows that the ORR rules' performance is strongly dependent on the planning system, and that ORR rules can be considered moderating variables. Further, the study develops a variance control framework that indicates the necessary managerial actions to improve shop performance. This paper demonstrates that the planning system, not the shop floor control system, is the major determinant of shop perfor...

Process planning was traditionally considered as manufacturing preparation that provides manufacturing methods and operation instructions. The process planning has become an important part in computer integrated manufacturing environment. To increase flexibility in a production life cycle, process planning has to play a significant role by dealing with dynamic activities and time-dependent problems from product design to shop floor manufacturing. The approaches to process planning actually refers to the approaches to the design of computer aided process planning systems. Generally there are two conventional approaches, the variant approach and the generative approach. The nature of process planning can be generally described as knowledge-intensive. The knowledge involved is mostly subjective, nondeterministic, nonheuristic, and difficult to represent. Process planning is time-dependent and dynamic. The planning functions being capable of dealing with dynamic changes in manufacturing processes and manufacturing requirements have far-fetching importance in modern manufacturing environment.

Symbiotic simulation is a paradigm that emphasizes a close association between a simulation system and a physical system, which is usually beneficial to at least one of them and not necessarily detrimental to the others. Aimed at extending previous work in symbiotic simulation, this paper proposes a framework of symbiotic simulation that can be used to improve the performance of a production system controlled by an enterprise system. A tube manufacturing shop floor has been selected as an example to demonstrate how the framework of symbiotic simulation can be implemented in a commercial off-the-shelf simulation tool. Experimentation has been carried out to evaluate the extent to which the symbiotic simulation can deal with uncertainties and disturbances in manufacturing systems. Early trials of the framework have indicated that it is capable of extending the existing applications of symbiotic simulation beyond engineering domains, especially manufacturing and shop floor control systems.

Shop Floor control systems: From design to implementation: A. Bauer, R. Bowden, J. Browne, J. Duggan and G. Lyons Chapman & Hall, London (199?), 344 pp £24.95 ISBN 0-412-58150-7

Spurred by the increasing competition among the Electronics Manufacturing Service (EMS) providers and in response to the needs of the Original Equipment Manufacturers (OEMs), a new model of manufacturing that epitomizes an integrated and predictive manufacturing environment is being proposed. The dynamic nature of the EMS environment mandates the need for a manufacturing schema that is both integrated and predictive (rather than reactive). This research is part of an ongoing effort to establish an integrated predictive manufacturing model through the concept of ‘continuous improvement’. The first step was to perform a general analysis of the operational structure and losses in a manufacturing environment. Once the losses were identified, they were grouped into equipment, production, process, operational, and material related losses. The key performance indicators for monitoring the variety of losses were identified. Process, equipment, operational and production monitoring tools were developed based on these performance indicators. Based on this understanding, a formal requirement specification was established. Shop floor control systems that provide on-line information on Work In Progress (WIP) status, defect-data, finished goods ‘genealogy’ and unitlevel traceability through data captured throughout the entire manufacturing cycle are being developed and implemented. Process metrics like first pass yield, Defects Per Unit (DPU), and Defects Per Million Opportunities (DPMO) are shared with shop floor personnel in real time by the application of proven Internet technologies. Real time Statistical Process Control (SPC) charts and process triggers, which serve as proactive tools in predicting ‘out-of-control’ situations, were also developed. Process metrology tools were developed through interfaces developed for inspection equipments like Automated Optical Inspection (AOI) and X-ray Laminography. Since a major portion of electronics manufacturing at an EMS provider is performed by capital intensive Surface Mount Technology (SMT) equipment, the performance of these pieces of equipment plays a major role in deciding the performance of the line, which in turn impacts the performance of the plant. Therefore, an integrated system with the capability to collect real-time data from production equipment and provide information on critical performance indicators like machine/line/plant utilization, downtime and component placement reports, which enhance the operational efficiency of the plant, are being implemented. Standardization of manufacturing practices and documentation and their influence on reduction in manufacturing lead-time is investigated in this paper.

To achieve competitiveness in the today’s manufacturing plants; many researchers suggest agent based manufacturing systems, with scheduling and control activities distributed on several entities called agents. To develop this kind of systems some promising agent-oriented software methodologies, as Gaia, have been proposed. They provide the concepts and procedures to define the main features of multi-agent systems. In this paper we show how we used the Gaia methodology to analyze and design a multi-agent-based shop floor control system that has been further implemented by JADE. We also show preliminary computational experiments that show as our approach has a good performance in flexible environments.Key Words: shop floor control, scheduling and control, multi-agent systems, software engineering, Gaia analysis and design.Análisis y Diseño Gaia de un sistema multiagente de control de plantaResumen: Para mejorar el desempeño de las actuales plantas de producción, muchas investigaciones sugieren la implementación de sistemas de fabricación basados en agentes, donde las actividades de programación y control de la producción están distribuidas sobre varias entidades denominadas agentes. Para desarrollar este tipo de sistemas, durante las dos últimas décadas se han propuesto varias metodologías que proporcionan los conceptos y procedimientos para definir las principales características de los sistemas multiagente. En este ar tículo se muestra el proceso de análisis y diseño de un sistema multiagente de control de planta mediante Gaia, una de las metodologías de desarrollo de sistemas multiagente más aceptadas en la actualidad. El sistema ha sido posteriormente implementado mediante JADE. También mostramos algunos resultados experimentales que muestran que el desempeño de nuestra propuesta en entonos flexibles es satisfactorio.Palabras clave: control de planta, programación y control de la producción, sistemas multiagente, ingeniería de software, análisis y diseño Gaia.

The Impact of Order Release Strategies on Leadtime and Tardiness : A Study on Shop Floor Control System

A Review of: "Shop Floor Control Systems: From Design to Implementation". By A. BAUER, R. BOWDEN, J. BROWN, J. DUGGAN and G. LYONS. (Chapman & Hall, 1991) [Pp. 344], £35 Hardback. Level: manufacturing professional/ student.