1. Introduction
For the past several years, manufacturing enterprises have increasingly become information integration in line with the introduction of CIM (computer integrated manufacturing) and FA (factory automation) systems. The tendency toward being information integration has rapidly increased and the use of information integration systems have been widespread. In the field of information processing technology, on the other hand, computer down-sizing and using the communications technologies such as the Internet have remarkably evolved. Since enhanced capabilities are now brought about by such technological advances, it seems only natural that they begin to be used in the factories. As a result, a lot of control systems having a host of information functions are introduced into the shop in the factories, making information integration factories real.
In addition to the technical aspects, the manufacturing enterprises should realize the necessity for overseas expansion of factories, lengthening of facilities life cycle, and introduction of management information systems.
Therefore, manufacturing enterprise want to make a distributed type of CIM system. In order to make a distributed type of CIM system, the use of open manufacturing systems and packaged factory software now begins to be highlighted.
The latest report on the introduction of open manufacturing systems.
2. Open manufacturing systems
The manufacturing system structure is now beginning to switch from centralized CIM type, which is centered around a large host computer or large-scale database, to a distributed type in which a large number of personal computers and other small-size computers are joined to form a network. Manufacturing system decentralization is made feasible because various small-size computers have improved in terms of capabilities to enhance their reliabilities. In the shop, centralized manufacturing systems are not favored because they entail heavy investments at the building time for manufacturing system. Instead, a distributed type is preferred as it is convenient for situations where partial system constructions are called for from time to time.
It is now possible that NC machine tools and PC(programmable controller), which have been controlled by dedicated controllers, will be controlled by personal computers. Various boards and software for use in such situations are now commercially available.
The resulting environment is suitable for situations where personal computers are used to perform information processes which have so far been executed by large-size computers, and control processes which have previously been conducted by dedicated controllers.
When personal computers are used to construct a distributed manufacturing system as described above, individual applications can be designed while taking into account the operating characteristics of distinctive subsystems or other elements of a manufacturing system unlike the previous method by which a manufacturing system was constructed while giving priority to overall manufacturing system optimization. Therefore, the introduction of such a distributed manufacturing system is expected to establish a system suitable for workers and managers.
Further, if the product and manufacturing management system are partly changed while a distributed manufacturing system is employed, it is expected that proper follow-up can be promptly taken simply by making changes corresponding to the changed portions without altering the whole system.
In other words, when a distributed manufacturing system is constructed, it is expected that an original manufacturing system can be formulated to suit the characteristics of individual enterprises and work places and that a created distributed manufacturing system will be able to promptly cope with changes in the market and environment for long periods of time.
To realize such a distributed system, however, it is necessary that a large number of and a wide variety of software programs. It is also necessary to furnish software that matches various characteristics of jobs and operations. If such software is developed originally, larger investments might be required than in the case of a conventional centralized type. It is therefore necessary for a distributed manufacturing system to employ package software for the purpose of reducing the software development cost and maintenance cost.
To realize a system which makes effective use of the advantages of a distributed system and eliminate the above-mentioned worries, it is essential that the processes of all system configuration elements be completely independent of each other and clearly defined, and that the relationships between such independent elements be clearly established, and further that proper information exchanges be achievable while all the independent elements are operable in a common operating environment.
To fulfill the above requests from the shop in the factory, it is necessary to ensure that (1) individual system configuration elements clarify their interfaces, (2) and that the subsystem functional structure is explicitly defined, (3) and further that compatibility is establishable via a common platform.
More specifically, it is necessary to model and clarify all job functions, classify them into appropriate independent units, and freely (openly) combine job functions to establish a proper system functionality.
Establishing an open manufacturing system means to classify manufacturing system component devices and software programs into appropriate units, clearly define their relationships, and provide means of freely combining them on a common platform.
3. Modeling a manufacturing system
For manufacturing system overall opening, modeling is frequently done according to an object-oriented modeling method, which regards all manufacturing system elements as objects in order to handle them as independent elements and combines them to form a large-scale system (Figure 1). Examples are "CIM Application Framework (proposed in 1995)"1)2) proposed by SEMATEC, which is a research and development association for U.S. semiconductor manufacturing industry, "Object-Oriented Manufacturing Execution System (proposed in 1995)"3) proposed by Manufacturing Science Center (NCMS) in USA, and OPC (OLE for Process Control) which aims to exercise process control using Microsoft's OLE (Object Linking and Embedding).
Fig. 1 Distributed system concept structure and open system introduction (see Word file for better viewing of the figures)
The basic structure of a recent distributed manufacturing system is such that manufacturing functions are regarded as objects, which are independent elements, and combined to create a standard model, and that the objects are combined on a common platform such as CORBA and OLE. The structure of an open system is such that there is no need to be aware of hardware or software differences as far as a common platform is used.
4. Trend toward the introduction of open manufacturing systems
The introduction of open manufacturing systems entails, by its nature, standardization which has to be cooperatively completed by several enterprises. It is not to be accomplished by a single device manufacturer or software manufacturer. It is also well to remember that standardization for open system establishment is meaningless if the relevant technical specifications are not released. Operations for standardization must be openly carried out.
These activities are conducted on various levels such as the introduction of open manufacturing system overall structure and open devices. Some typical activities are described below.
As regards the manufacturing system overall structure, there are activities related to the aforementioned "CIM Framework" of SEMATIC in the U.S.1)2) and activities related to "Object-Oriented Manufacturing Execution System" (proposed in 1995)3) which is proposed by Manufacturing Science Center (NCMS). In Europe, there are standardization activities such as "CIM Open System Architecture" which is promoted by CEN, European standardization organization. In Japan, various activities are conducted including the object modeling activities 4) which are performed by Japan FA Open Systems Promotion Group of Manufacturing Science and Technology Center (MSTC).
In relation to the introduction of open software for a FA system and its platform, the Object Management Group (OMG), which is centered on the U.S. and promoting the object-oriented software standardization organized a manufacturing industry group (Manufacturing Special Interest Group which is abbreviated MSIG), made a request for objectification, compiled relevant activities, and issued the "Manufacturing Enterprise System White Paper" in 19965). The task force (MTF) has been organized to study the basic specifications for manufacturing industry objects on the basis of the white paper, and is now going to investigate the details.
The promotion of open control device introduction is centered on the U.S.A task force for establishing a process control system which uses Microsoft's OLE environment is operated under the leadership of Allen Bradley. In Japan, the Japan FA Open Systems Promotion Group of MSTC has begun to study the specifications for common interface introduction for control devices on the basis of "Autonomous Distributed System" of Hitachi, Ltd.
As regards manufacturing system configuration elements, some well-known activities for open system introduction relate to CNC control devices and PCs (Programmable Controllers). For example, TC184/SC1/WG7 of ISO (International Organization for Standardization) has begun to study the standard specifications in accordance with EU (European Union) project development results. In Japan, several groups are performing activities with a view toward the introduction of open systems. For example, the OSE (Open System Environment) Research Group, which is organized by 19 companies including Toshiba Machine, has demonstrated a system in which the CNC open system architecture (OSEC: Open System Environment for Control)6) is incorporated.
5. Development MES system for Machining
In order to realize the open manufacturing system, JOP is developing the Open MES system. The developing MES is the following figure (Fig2).
Fig 2 MES Framework
The MES has an object oriented Model which is show in Figure 3. This model is based on the SEMATEC model.
Fig.3 Object Model in MES (see word document for better readability of figure)
The MES system is developed by IBM,Japan, Toyoda Machinary Ltd., and some software houses.
5. Future of open manufacturing system use
Manufacturing systems have become increasingly information integration. There is now an increased demand that manufacturing system functions be modeled to offer open systems, thereby facilitating the system configuration by multiple vendors and creating systems suitable for individual user characteristics. As stated earlier, many activities have been performed for standardization and other relevant purposes.
Recent activities for the introduction of open manufacturing systems are characterized by the fact that they do not aim to establish a single standard or interface that covers the whole manufacturing system but intend to offer a practical, open system by, for instance, setting up a loosely defined standard that may incorporate various other standards and describing the target process as a model to maintain transparency instead of aiming for interface standardization only.
When an open manufacturing system is to be actually introduced, there are many problems to fix. For example, information processing related problems must be cleared up by checking whether invested assets and accumulated information assets can be effectively used in an open system and whether two or more variously specified open systems can be interconnected. There are also manufacturing technology related problems which have to be solved by assuring the reliability and dependability of manufacturing processes where products are incessantly manufactured.
References
1) SEMATECH: Computer Integrated Manufacturing (CIM) Application Framework, Specification 1.2, (1995)
2) SEMATECH: Computer Integrated Manufacturing (CIM) Application Framework, Specification 1.3, (1996)
3) NCMS: Object-Oriented Manufacturing Execution Systems: A New Approach to Agile Manufacturing Information and Control Systems, Final Report, Vol. 1, (1996)
4) International Robot FA Center: Prospectus for Japan FA Open Systems Promotion Group (1996)
5) OMGMSIG: Manufacturing Enterprise Systems, A White Paper by OMGMSIG, Version 1.0, (1996)
6) OSE Research Group: OSE Architecture Version 2.0, (1996)
7) NIIIP: National Industrial Information Infrastructure Protocols Documents, Revision 6, (1995)