CAD-integrated__ engineering-data-management system for spring design.pdf

Pergamon Robotics engineering data management; product data management; spring design; relational database 1. INTRODUCTION In the last decade, several research papers have reported the development in engineering design databases. 1,4-8 In general, most of the engineering processes are series and can be summarized as an iterative system with three essential phases: con- ceptual design, engineering design/analysis and detailed design. 13 Within each phase, there are many activities to be performed. A designer should complete all necessary activities and coordinate them to achieve the objectives in the stage. After completing an intermediate phase, the designer then moves on to the next phase. In general, a designer iteratively performs revisions in phases to satisfy the design objectives. In an iterative design process, engineers may use a variety of software to complete a complicated design job. In the process, many engineering data need to be managed properly. However, owing to the lack of an integrated environment, these data are kept in different formats in separate systems. For example, designers generate a large amount of data in the design and analysis phase. There is descriptive information to identify the functional specification, and values of graphical parameters to create the engineering drawing. On the other hand, most of the traditional CAD packages only provide the drawing file format or standard data exchange file formats 271 (e.g. DXF, IGES or STEP). 5 Owing to the complex- ity of these CAD file formats, it is difficult for engineers to modify the design drawing through modification of CAD files even in routine design/ redesign activities. In more specific domains, en- gineers can generally identify the graphical or descriptive parameters that are important to the routine design. The important data that cannot be kept on the engineering drawing are normally stored in a traditional table-based database. In the spring industry, the design processes of spring products involve standard and routine activities that are well known and widely accepted. 21 In most cases, designers only modify the same data of an existing product to define a new product. A key issue to managing the engineering data is to define the feature-based product model. The system uses the product model to identify which parameters can be modified to generate a new product and which engineering data need to be edited and stored. As indicated above, if engineers only keep engineering data in a CAD file format, the management of engineering data is very inefficient. The engineering data can be stored in a traditional relational database, text files, worksheets, etc. Because of the software limitations, CAD software will find it difficult to access these data directly. Thus, the engineering data and drawings are handled sepa- 272 rately. When the revision of a design occurs in a separate CAD system, the related data cannot be simultaneously modified in the engineering database. The integration of data and drawing becomes an important issue for managing data efficiently. Furthermore, a CAD system is a software system designed primarily to create, manipulate and store product engineering drawing. It generally provides well-defined lower-level drawing commands. For a spring manufacturer who does frequent minor redesigns, it may be a good idea to support a well- designed human-computer interface in order to save the efforts spent in driving a regular CAD package. Therefore, how to design a human-computer inter- face for managing the engineering data and drawing is another important issue. Among all commercial CAD systems widely used in PCs, AutoCAD is chosen as the example system for the CAD-integrated engineering-data-manage- ment system (EDMS) development. AutoCAD has several-properties that can assist us in developing the CAD-integrated EDMS. First, AutoCAD is a widely used PC-level system in the component manufactur- ing industry, and it provides enough flexibility in drawing-generation. Second, AutoCAD provides the application development module, called AutoCAD development system (ADS) for programming devel- opment. The syntax of ADS is compatible with the C language in order to keep the portability. In addition, there is an AutoCAD tool, called dialog control language (DCL), which assists users in developing human-computer interfaces in CAD-integrated EDMS. The interfaces defined by DCL can function according to the ADS command specification. Finally, AutoCAD provides the database interface module, AutoCAD SQL extension (ASE), to enable AutoCAD to access data tables from a relational database management system (DBMS). This paper is organized into several sections. First, the method of constructing the CAD-integrated EDMS for spring design is described. The basic components in the CAD-integrated EDMS are also identified in this section. Second, the product model for spring design is described. Using the relational database system, the database structure for storing the engineering data is also established. Third, we introduce the communication components to achieve the data share between databases and CAD tools. Finally, the design of a user-system interface for the CAD-integrated EDMS is discussed. Using the AutoCAD ADS module, a user-friendly interface can be designed in order to achieve interactive engineering data manipulation. Examples of the software system run are shown in order to illustrate the techniques at work. 2. ENGINEERING-DATA-MANAGEMENT SYSTEM In a design environment, there are many formats (types) of data being accessed or assigned during the Robotics however, it is definitely a main focus of future research. Based on individual product shapes, the spring product can be regarded as a combination of several feature shapes. As illustrated in Fig. 4, the product is an example of a spring product. There are two main feature elements combined to form the spring, which are main core and extended elements. As shown in D,t .,. 0ment Sy 0m 1 Communication Component Data Exchange iemporary Stoag_o User-System Interface Product Definition Product ID Product Description Product Feature Design Validation Database Management Support Retrieve Query Modification Backup/Rc_.overy J I CAD-Tool Product Drawing Model CAD-Tool Product Drawing Model CAD-Tool Product Drawing Model Engineering Drawing Pig. 3. The architecture of the EDMS. 274 Robotics the offset (space) may exist or not exist between each circle; and the direction of the core may be clockwise or counter-clockwise. For the extended elements, there are many different styles for the functional needs. Thus, the spring products can be divided into several specific product categories based on these features. Since there is a variety of extended elements, the feature of the main core is used as the basis to classify the spring products into four specific product categories. Then, the springs are further classified into several sub-groups for each category. In the same sub-group, there are some product types based on a variety of extended element styles. After classification, the parameters necessary to generate the product drawing for each product type are identified. In addition to the graphical product data, the product descriptive data should be linked with the information of product geometric representation, such as the materials used in manufacturing, the vendor information, manufacturing processes, and some other functional specifications. Given the product model, the types of data to be accessed from data files and the suitable database structure for storing engineering data are determined for the system implementation. Because relational databases have gained wide acceptance in industry, 14 both product description and product geometric feature parameter values are stored in a relational database system. For the feature-based data, table formats are created to define features and their associating parameters in order to be applied in the geometric specification. Both types of data tables are properly linked to each other and to the lower-level CAD data files. In this paper, FoxPro DBMS is used to construct the database for storing engineering data. Based on the product model for spring design, the database structure is defined as shown in Fig. 6. In the database, the first field is to store the identification (ID) for every spring product. Then, the following several fields are defined to store the parameter values of the features. The number of fields depends on the complexity of the product shape. For springs within a product type, the number of fields is fixed. In addition, we provide fields to store the descriptive data, such as the materials used (Material), the vendor information (Vendor), manufacturing meth- ods/processes (Mfg_pro), and some functional specification (e.g. Stress). By use of the communica- tion components, feature-based data can be properly linked to the standard product drawing modules that are constructed by the CAD tool. Further, the product drawing module can generate the engineer- ing drawing according to the specified data. 4. CAD AND PRODUCT DATABASE COMMUNICATION The CAD-integrated EDMS combines the CAD tools and management system. The linkage of CAD tools and database can be achieved through establishing the communication component. The communication component in the CAD-integrated EDMS is responsible for (1) accepting requests from the system users for data manipulation, (2) transfer- ring data back and forth between database and CAD tools, and (3) returning the results of CAD operations to the database. In this paper, AutoCAD is the CAD tool in EDMS. As described in the previous section, descriptive data are main components of product s/i., L Closed without offset J L I Clockwise Countetoclockwise Clockwise I Stylel Style2 . Style n Spring product i I Constant -I Non-closed with offset I Counter-clockwise Ordinary spring ? I Variable The d/ameter ofmaln core is a constant or a variable? The offset between each circle is zero or positive (e.g., Fig. 4)? The direction of core, in topview, is clocl.4se or counter-cloclcse from top to bottom? The styles of Ictended elements Fig. 5. The classitication of spring products. CAD-integrated engineering-data-management system T.-K. PENG and A. J. C. TRAPPEY Field Type Width Decimal ProductlD Character 10 ProductlD Parl Numeric 8 2 Par2 Numeric 8 2 Par3 Numeric 8 2 Par. Numeric 8 2 Product feature-based data (parameter) Material Character 10 Mfg_Pro Character 10 Vendor Character 10 Stress Character 10 Product 3). descriptive data Fig. 6. The database structure for spring design. 275 design. It is not easy to handle the non-geometric data by using earlier versions of AutoCAD software. Recently, ASE has been supported as a programming library for directly accessing external databases. Thus, we can utilize the library to establish the communication component between AutoCAD and external database, z3 Since the relational database management systems are chosen to establish the EDMS databases, it accepts the SQL statement for database manipula- tion. Through the use of ASE, the communication component of CAD-integrated EDMS can be established and gain the following benefits: supporting the interface to link with general DBMS without developmg an extra driver to handle a specific DBMS; supporting SQL interpretation without writing DBMS-specific codes; enabling the use of non-graphic data in design and drafting tasks. The communication component consists of two levels. As shown in Fig. 7, the first level is a database driver, which supports the linkage between MMS and our communication application. The second level is the driver-independent communication application, which handles communications between the application program and the database driver. The driver performs syntax checking and execution of all the SQL statements in accessing or editing database. The communication application accepts or sends data to the database. If necessary (particularly when data are transferred through the network), a temporary storage on the CAD tool is created to Communication Application IIII SQL data support Database access (Network) Database Server ADS/ASE Application II t Interpreter Database Driver Database access _ I Database files Fig. 7. The architecture of the communication component. 276 mauiplate the transferred data efficiently without causing too much network traffic. 5. USER-SYSTEM INTERFACE The CAD-integrated EDMS has been developed to assist the CAD users in accessing data stored in a DBMS to accomplish their routine tasks (such as design or drafting). If the system provides interfaces for the human-computer interaction with buttons, menus or input dialog boxes, users can efficiently apply both CAD and DBMS functions to their full capacities. 10,12,16,19 There are five primary methods for human- computer interaction: 11719 Menu selection - in which the user picks up the one most appropriate item from a list of selectable items, then the system applies the built-in subroutine to achieve the selection and return the results of the selection. This method is generally the simplest way for less-experienced users to operate the system without memorizing the commands. Command language - in which users who under- stand the associated syntax well can initiate complex procedures rapidly. Whether the level of command language is lower or higher, the error rate may be high and user training is necessary. Forms - in which data entry is required to fill in blanks. After the users input data to the blank data fields, the system accepts the data and stores it in the template space. This method is particularly useful for handling the DBMS entry. By the use of forms, users can understand which data are to be entered, edited or deleted without having to memorize the DBMS-specific commands. Natural language in which users are allowed to input ordinary conversational dialog and the Robotics & Computer-Integrated Manufacamng Volume 12, Number 3, 1996 system is able to understand it. It is not easy to implement this method because of the complexity of natural language. Direct manipulation - in which the user can use graphical representations that look like those available in the real world. For instance, the use of a graphical icon is one form of direct manipulation. Based on the classification of spring products, the system applies the menu selection approach to construct a sequence of dialog interfaces. With the limited number of buttons, a user can quickly select the right product type. In addition, there is a DBMS- accessing interface for each product type. The DBMS-accessing interface is a form-type panel format. As shown in Fig. 8, there are several input boxes for data entry. Users only input data into the corresponding input boxes without having to learn the database structure and locations. In this inter- face, by the use of function keys, the EDMS will respond to a users request, such as data viewing, deleting, inserting and changing. The product IDs are shown in the left-hand-side list box which is also constructed based on the menu selection approach. When the user picks an ID, a sketch of the selected object is shown in the demo drawing frame, and the specific engineering data (geometric representation and product description), retrieved from the data- base, are also displayed on the input boxes (shown in Fig. 8). These data can be directlyaltered for redesign on the input boxes. The corresponding DBMS updates are simultaneously executed without additional effort from the spring designer. The user confirmation of design specification Coy clicking the OK button) will generate the corresponding engineering drawing on display. Product NO. 1 Product NO. 2 Product NO. 3 Product Demo Drawing Product Description Data i ii II . It li Csomi.c ltion Data i i i i i I C- )( , )C )C, )C )C ) Command Buttons Fig. 8. The DBMS-accsing interface for the CAD-integratl EDMS. - Input Boxes CAD-integrated engineering-data-management system T.-K. PENG and A. J. C. TRAPPEY 277 m J I II qle C.CADMNDSCAD.E loaded. 2ommend: spdng Fig. 9. The first classification dialog interface. 6. EXAMPLE This section provides an illustration to show how the CAD-integrated EDMS operates. Spring products are classified into several sub-groups based on their main shape features. Further, there are several product types in each sub-group. For each product type, there is a standard drawing module for generating engineering drawings based on values of predefined feature parameters. Engineers can pick up a suitable product type from a sequence of dialog interfaces as shown in Figs 9-11. After an engineer confirms a product-type selection, the system will display the DBMS-accessing interface corresponding to the selected product type. For example, select C CC 001 type after clicking Spring C category in the first dialog interface, CC sub-group in the second dialog interface and finally C CC 001 in the third dialog interface (Figs 9-11). The DBMS IJ o -S NG emil . x . i I I . I - I . lll . I -ire .ANSC.E loaded. 3ommemd: spring Fig. 10. The sub-groups in the C-type category. 278 Robotics & Computer-Integrated Manufacturing Volume 12, Number 3, 1996 I,J , c cc_002 c_cc 003 J U 3ommand: spring locodwin/ad s/syste rn/cccO 01 _o Fig. 11. The product types in the CC sub-group of the C-type category. accessing interface of C CC 001 product type is displayed as in Fig. 12. In Fig. 12, there are s