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Database Development for Supporting Machining of Prismatic Components* A. M. Shaharoun 1, A. A. Razak 2, M. I. Jambak 3 Faculty of Mechanical Engineering Universiti Teknologi Malaysia Locked Bag 791, 80990, Johor Phone: +60 - 07 - 5504566 Fax: +60 - 07 – 5566159 1 E-mail: [email protected] E-mail: [email protected] 3 E-mail: [email protected] 2 ABSTRACT Machining processes are operations of metal removal by turning, shaping, planing and milling. Machining processes are common within a Flexible Manufacturing System (FMS) and carried out by computer-controlled operations. In order to operate efficiently, an FMS requires a complete set of information to assist its operation. Therefore the design of the information system has to be performed taking into consideration all the functions and entities that operate within an FMS. The modelling work in this research will be on capturing the activities on the shop floor focusing on the machining of prismatic components. IDEF suite of modelling software will be used to come up with the functional and information model. Issues of architecture, for instance the flexibility and adaptability of the database are highlighted during the modelling phase. The approach adopted in this research is to start the development work using a relatively small-scale database management system (DBMS) and later expanding the scope and migration into a wider scale DBMS. The database will be of assistance to researchers and companies who use extensive machining processes for their operations and who intend to integrate their operation into an FMS. Such a database will also act as a precursor for a more extensive database such as those required to operate a Computer Integrated Manufacturing (CIM) system. Keywords Database, Information System, Flexible Manufacturing System, Prismatic Components, Modelling, Computer Integrated Manufacturing methodology and tools used in developing the database for supporting machining of prismatic components. INTRODUCTION Industry is today characterised by automation. Engineering processes such as machining, fabrication etc are mainly performed by computer-controlled machines that perform the operations automatically and often integrated into a system such as FMS. As a computer-controlled system, an FMS is an information-driven system. The attributes of an information system that impact the operation on the shop floor are the quality of information, reliability, consistency and concurrency control, speed of operation, and adaptability (Veeramani et al., 1993). One of the challenges in developing the database is to organise all the data into a useful, accessible and logical form (Hannam, 1996). Two strategic approaches for tackling this problem are creation of the information model that maintain its characteristic of wide applicability and flexibility, and use of a CIM architecture (Hannam, 1996 : Singh, 1997). The database in this paper is developed based on the initial information architecture. This paper describes the database state-of-art, the requirements of the database, the strategy, the * DATABASE STATE-OF-ART A database is a place where data can be stored and retrieved. A database is controlled by a software system that performs the function of defining, creating, and revising the database called database management system (DBMS) (Singh, 1997). Vernadat (1994) gave at least five standard requirements of a database: - Data independence: Physical data-storage aspects are independent from logical data description and manipulation, and are unknown from user applications. - Data sharing: Data can be shared and accessed concurrently by different user and/or applications. - Controlled data redundancy: The same information must be stored once. - Data integrity and security: Rules can be expressed and verified to ensure that the state of the database is semantically correct. - Ad hoc query facility: Queries on data can be expressed and executed to provide answers to questions formulated by application or on-line users Shaharoun, A.M., Razak, A.A., Jambak, M.I. (1999), “Database Development for Supporting Machining of Prismatic Components “, In Proceeding of World Engineering Conference ’99, Kuala Lumpur, 19th – 22nd July 1999, pp. 483-488 The concept of database is data integration based on a three-schema model (Hsu, 1994 : Hannam, 1996 : Singh, 1997), they are briefly described as below: - Internal schema: Represents the physical organisation and storage of the information. - External schema: Describes the use of information. Users view only the portion of data that concerns them in their own preferred ways as if these data were structured exclusively for their software environment. - Conceptual schema: Represents a composite view of a common pool of shared data. The integration takes place with the conceptual schema, which is the community representation of the consolidated data, sources and is precisely the heart of the database model. characteristics (i.e., extendibility, expandability, and adaptability). The information architecture is needed in response to the evolutionary nature of integrated manufacturing, because the changes in requirements in integrated manufacturing will inevitably affect dependency relationships and information flows among inter-operating functional modules in the system. Figure 1 shows the role of information architecture for developing the database to control the FMS: However, the architecture is a conceptual one and not a concrete physical property of a system. Thus, the architecture should be visualised by means of a symbolic model to represent the system. Depending on how the conceptual schema is constructed, there are four major types of databases (Hsu, 1994 : Elmasri et al., 1994): hierarchical, network, relational, and object-Oriented There is another type of database but not so common at present called Object-Relational database. The database is founded based on the advantages of relational database and object-oriented database. The relational database is the mostly commonly used and well-supported form of database. Hsu (1994) found that relational and object-oriented databases are more flexible than others types. Furthermore, Singh (1997) described the potential of relational type as follows below: 1. Ease of use because the visualisation and clarity of data is represented by two-dimensional tables 2. All data is viewed in tables, thereby allowing easy data manipulation and query via Structured Query Language (SQL) 3. With the relational operations, a standardised and effective way of decomposing and recomposing relation is provided. This approach enables the incremental building of larger systems module by module 4. Security controls can be easily implemented where security authorisation will relate to relations to protect company sensitive attributes 5. The relational model support dynamic reorganisation (i.e. extension and modification to the structure) of the database without affecting existing application 6. Generally supported by high level non-procedural, set-oriented languages, such as 4GLs (fourth generation languages) to enable flexible access, management and presentation of data stored in the database. INFORMATION ARCHITECTURE The information architecture shows the subject area of information needed and used by an enterprise, and may include the entities and the relationships of those entities within the subject areas considering the architecture Figure 1. The role of Information Architecture In this research work, the functions and the information needs in the machining operation are modelled by using IDEF methodology before the database tables are created. IDEF “IDEF” is an acronym for the ICAM-Definition methodology – (Integrated Computer-Aided Manufacturing). The IDEF methodology was developed by the US Air Force’s ICAM program in the early 1980’s (Ranky, 1990 : Ang et al., 1989, 1994). IDEF methodology is a group of methodologies, which are used for modelling of particular aspects of a system (Sarkis et al., 1994 : Vernadat, 1996). IDEF™ integrated software by Meta Software Corporation was being used in this research. The IDEF™ suites provide IDEF0 for modelling the functions and activities of the system, and IDEF1x for developing the conceptual relational data model. In IDEF0 the functions are represented by blocks and linked together through inputs, outputs, controls and mechanisms (ICOM). Functions can be decomposed into sub-functions (Wu, 1992 : Sarkis et al., 1994 : Ang et al., 1994 : Vernadat, 1996). Figure 2 illustrates a block of an IDEF0 model. tools, and work-holding tools) of manufacturing information respectively Bugtai (1997). Figure 3 shows the manufacturing data structure. Manufacturing Information Process Machining Resources Fixturing Figure 2. An IDEF0 Diagram To model the information system, every entity in IDEF1x, is represented by a box and given a unique name with a parent entity having a relationship with a child entity. DATABASE REQUIREMENTS FOR SUPPORTING THE MACHINING OF PRISMATIC COMPONENTS The database for supporting the machining of prismatic components should fulfil the minimum requirement that was given in the previous section. Thus, the database could facilitate the frequent updating of information to increase the speed of operation. To do so the database should be able to capture all relevant information accurately and completely. It must be capable of meeting the short-term changes according to the need of production planning and should require minimal cost for long-term changes of a manufacturing system. The database should incorporate the process (machining and fixturing) and the resources (machine tools, cutting Machine Tool Cutting Tool Workholding Tool Figure 3: Manufacturing Data Structure (Bugtai, 1997) The database should support shop floor control operations to manage and control all the manufacturing activities, which take place at different locations on the shop floor. The information that is supplied by the database required to execute these activities has to be delivered to the right location. RESULTS Machining of Prismatic Components Functional Model Using IDEF0 System Figure 4 illustrates the third level of a manufacturing activities functional model. It is decomposed from the top level, and if necessary, it can be further decomposed to get more detailed model. Figure 4. Manufacturing Activities The system to be modelled assumes a small batch manufacturing system and the machined components in the system are defined to be prismatic components. According to Tiemersma’s (1992) reference model of Flexible Manufacturing Cell – where the manufacturing activities take place –there are at least five manufacturing activities on the shop floor: tooling, fixturing, material storing and retrieving/loading, transport system activities, and workstation activities. Every activity or the function is capable of being decomposed to the lower level. For example, in the tooling activity, tool identification, tool assembling and loading/unloading to the transport system activities are located in the lower level of the model. Information Modelling Using IDEF1x In determining the information flow, the IDEF0 function was analysed. The components in the IDEF0 blocks, i.e. input, control, output and mechanism (symbolised by an arrow) give an understanding of the information that needs to be captured. Figure 5 shows an example of the tool information model based on the IDEF0 block number A41 (Tooling). The constructed model shows the entities, the attributes, and the relationships from the tool point-of-view. Figure 5. Tool Information Model The tool entity was created first, and then its children. In this case, the children of the tool entity includes tool assembly, tool-holder, tool parameter (which is shown in figure 5) and other entities like shank, cutter-edges, etc. Database Tables Construction CREATE TABLE TOOL ( tool_id CHAR(21) NOT NULL, tool_name CHAR(20) NULL, supp_code CHAR(10) NULL, picture CHAR(50) NULL ); CREATE UNIQUE INDEX IXTOOL ON TOOL ( tool_id ASC ); CREATE TABLE TOOL_ASSEMBLY ( insert_code CHAR(10) NULL, Screw_code CHAR(10) NULL, tool_id CHAR(21) NOT NULL ); CREATE UNIQUE INDEX IXTOOL_ASSEMBLY ON TOOL_ASSEMBLY ( tool_id ASC ); CREATE TABLE TOOL_HOLDER ( holder_code CHAR(13) NULL, tool_id CHAR(21) NOT NULL ); CREATE UNIQUE INDEX IXTOOL_HOLDER ON TOOL_HOLDER ( tool_id ASC ); CREATE TABLE TOOL_PARAMETER ( tool_diameter DECIMAL NULL, tool_length DECIMAL NULL, length_L4 DECIMAL NULL, length_Lc DECIMAL NULL, hold_diameter DECIMAL NULL, tool_model CHAR(10) NULL, tool_id CHAR(21) NOT NULL ); CREATE UNIQUE INDEX IXTOOL_PARAMETER ON TOOL_PARAMETER ( tool_id ASC ); Figure 6. IDEF1x SQL Commands system can be easily refined into greater detail until the model is as descriptive as necessary for the decisionmaking task at hand. The hierarchical nature of IDEF0 facilitates the ability to construct (AS-IS) models that have a top-down representation and interpretation, but which are based on a bottom-up analysis process. In fact, In the implementation stage, the information model is used to create the tables for the database. There are two ways of creating the tables. The first option is to directly create the table using table wizard facility in the DBMS. The second option is export the IDEF1x model to the SQL file and execute the commands in the file to create the tables. The SQL commands shown in figure 6 below are created by using the export facility in IDEF1x. Figures 7 and 8 show the database table and its user front-end respectively. DISCUSSIONS The primary strength of IDEF0 is that the method has proven effective in detailing the system activities for function modelling. The description of the activities of a Figure 7. The Database Table Figure 8. Database Front-End one of the observed problems with IDEF0 models is that they often are so concise that they are understandable only if the reader is a domain expert or has participated in the model development. database system is capable of being scaled up to a larger system such as those required by a CIM system. The strength of IDEF1x lies in its roots and the weakness of IDEF1x is that the modeller must be experienced in order to create good models. This research is conducted under IRPA project vote number 72091 for the Faculty of Mechanical Engineering, Universiti Teknologi Malaysia. One of the problems of database development is the nonuniformity of SQL commands for different system. For example, figure 9 below shows the difference between IDEF1x and Oracle DBMS SQL commands for the same set of instruction. REFERENCES IDEF1x SQL: CREATE TABLE TOOL_ASSEMBLY ( insert_code CHAR(10) NULL, Screw_code CHAR(10) NULL, tool_id CHAR(21) NOT NULL ); Oracle SQL: CREATE TABLE TOOL_ASSEMBLY insert_code CHAR(10) NULL, Screw_code CHAR(10) NULL, tool_id CHAR(21) NOT NULL; Figure 9. Differences in SQL Commands CONCLUSION This paper has described the requirements for a database for supporting the machining of prismatic components. The functional and information models were developed using IDEF methodology. The database is generic and will prove useful to researchers and companies who intend to or are already implementing automated machining systems. The system architecture is capable of operating in a highly dynamic and frequently changing manufacturing system environment. This ACKNOWLEDGEMENT Ang, C.L. (1989), “Planning and Implementing CIM”, Computer-Aided Engineering Journal, October, pp. 167 – 176. Ang, C. L. et al. (1994), “Automatic generation of IDEF 0 models”, Journal of Intelligent Manufacturing, 5, pp. 79 –92. Bugtai, N. and Young, R.I.M. (1997), “Information Models in an Integrated Fixture Decision Support Tool”, Proceeding of 13th International Conference ComputerAided Production Engineering, Warsaw, June 1997, pp. 87-94 Elmasri, R. and Navathe, S. B. (1994), Fundamentals of Database System, 2nd Ed., USA: The Benjamin/Cummings Publishing Comp, Inc Hannam, R.G. (1996), “Computer Integrated Manufacturing: from concepts to realisation” 1st Ed, England: Addion Wesley Longman Hsu, Cheng (1994), “Manufacturing Information System”, in “Handbook of Design, Manufacturing, and Automation”, Dorf, R.C. and Kusiak, A. (Eds), Canada: John Wiley & Sons Meta Sofware Corporation (1997), Design/IDEF User’s Manual for Microsoft Windows, Version 3.5, Cambridge Ranky, P. G. (1990), Flexible Manufacturing Cells and Systems in CIM, Guilford, Surrey, England: CIMware Limited. Sarkis, J. and Lin, L. (1994), “An IDEF0 functional planning model for the strategic implementation of CIM systems”, International Journal of Computer Integrated Manufacturing, Vol 7, No. 2, pp.100 – 115. Singh, V. (1997), The CIM Debacle, Methodologies to Facilitate Software Interoperability, 1st Ed, Singapore: Springer-Verlag Tiemersma, J.J. (1992), “Shop Floor Control in Small Batch Manufacturing”, Universiteit Twente: Ph.D. Thesis. Veeramani, D. et al (1993), “Information system architecture for heterarchical control of large FMSs”, Computer Integrated Manufacturing, Vol 6, No.2, pp. 76 – 91. Vernadat, F.B. (1994), “Database for CIMS and IMS”, in “Modern Manufacturing: Information Control and Technology”, Zaremba, M.B. and Prasad, B. (Eds), London: Springer-Verlag Vernadat, F.B. (1996), Enterprise Modeling and Integration: Principles and Application, England: Chapman & Hall. Wu, B. (1992), Manufacturing System Design and Analysis, 2nd Ed, London, UK: Chapman & Hall.