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1 外文文獻(xiàn)原文 A Feature-Based, Parametric Modeling System for CAD/CAPP/CAM Integrated System Abstract：To shorter product development time, this paper proposed an approach to developing feature based parametric product modeling systems which are suitable for integrated engineering design in CIMS environment. The architecture of ZD-MCADII and the characteristics of its each module areis managed by introduced in detail. ZD-MCADII's product data an object-oriented database management system OSCAR, and to the standard STEP. For the product model is built according the product design is established on a unified product model, all product data are globally associated in ZD-MCADII. ZD- iMCADI1 provides various design features to facilitate the product design, and supports the integrity of CAD, CAPP and CAM. I. INTRODUCTION With the increasing pace of technology development and international competition, today's industrial environment is asking for further improvement of design quality and efficiency. As a result, research and commercialization of modern CAD/CAM technology are focusing on the feature- based modeling [I], the parametric design, and even on CIMS(Con1puter Integrated Manufacturing System), to reduce the gap, which traditionally existed between design and manufacturing, and improve the efficiency of product development. So, feature technology and parametric design are playing a more and more important role in the modern CAD systems. The main reason lies in that feature-based design support the integration of CAD, CAPP and CAM systems, and parametric design will reduce product design cycle times dramatically. Solid modeling contributes to fast, efficient, competitive product 2 development, and can simulate the mass properties of physical objects (such as volume, moments of inertia, and center of gravity). In contrast, 3D wireframe and surface models only simulate the shapes of physical objects. So, the most of CAD/CAM developer choose solid model as geometric model of product. Ⅱ. OVERVIEW OF ZD-MCADII ZD-MCADII [2-51 is a product modeling system of Zhejiang developed by Artificial Intelligence institute is a feature-based parametric modeling system University. It integrated with CAPPKAM systems. The system is based on the achievement of the National 7th five-year-plan project -- "The research of the mechanical product CAD support software for VAX series (UNIX OS)", combined with the National 863 high-tech. Project -- "Product model basedCAD/CAPP/ CAM integrated system" in 8th five-year-plan period. This paper proposed an approach, which has been applied in our system ZD-MCADII, to develop feature-based parametric product modeling systems. The basic idea of the development of ZD-MCADII is to present all the product characteristics in a computer internal representation, to provide the modeling techniques that allow the definition and manipulation of those product characteristics, and to integrate with CAD, CAM systems in CIMS environment. Parametric modeling of ZD-MCADII can capture design to a intent and allows designer to make substantial changes part or assembly at any time during the design process. Parametric design offers a flexible approach to 3D-parametric modeling. It includes datum aides, such as pattern and group operations, coordinate systems, datum plane, datum curve, and datum point, that help improve designer praductivity. ZD- MCADII's 3D parametric model, 2D parametric and assembly model are associated globally so that any changes in onb or two of these models 3 will cause any other associated models be automatically updated. ZD-MCADII's sketcher allows designer to build dimension-driven profiles with geometric constraints such as, parallelism, tangency, and colinearity, captured automatically. Designer will be prompted by 'Smart-Line when these geometric constraints emerge. ZD-MCADII's constraints- based modeling allows designer to define equations bi- directionally relating model parameters to external engineering requirements which can then drive model geometry. Feature-based modeling in ZD-MCADII allows design to include standard design elements in product geometric model and eliminates traditional, time-consuming modeling operations, and it provides various design features to facilitate the product design. ZD-MCADII also allows designer to construct his own feature libraries with user-defined feature provided by ZD-MCADII's feature module. ZD-MCADII's feature editor allows designer to modify a feature on screen by selecting the dimension and entering a ne& 'vahe. User can create a feature from a profile that lacks any constraints or dimensions, and even better, he can add dimensions and constraints later by clicking the feature redefine icon simply. ZD-MCADII is able to convert design feature to manufacture feature used in CAPP and CAM by its feature mapping module. Ⅲ. THE ARCHITECTURE OF ZD-MCADII It is we11 known that an open software architecture brings ‘‘plug and play” compatibility and freedom of choice to software applications. So, as an excelient software, it must have an open architecture. From this view point, we pay much attention on its architecture while developing ZD-MCADII. 4 Fig. 1 and fig. 2 illustrate the architecture of ZD- MCADII. At the bottom of the diagtam, there is a developing environment interface which is independent of device. In this module, A VAPI (Virtual Application Programming Interface) for designers of application system is supplied. It is independent on the hardware and software platforms. VAPI brings much benefit, such as portable, flexible, expandable and reusable, etc. UI(User Interface) is an event driven GUI, it can be.a of window, command line, menu, dialog box, or other type interface that takes raw user input and generates a command stream, and provides graphic interaction. The functionsprovided by UI module are: 5 ?Visualized icons, on-line documentation and on-line help ?Multi-views displaying(automatic hidden), color shading. U1 provides dynamic display to respond to mouse movement and button events. ?Menu customizer ?Picking entities. Picked entities can be filtered using criteria, such as entity type, color, entity layer and display status, etc. ?Grid support. The grid allows snapping onto the active Construction Plane. ?User defined view PDPM (Product Design & Product Management) is the kernel of ZD-MCADII. PDPM treats the product design, including drawing design, part design, assembly design, and the product data management. PDPM has an ability to manage the full associativity of all models of the same product. Unlike traditional data management programs that focus on managingfiles, ZD-MCADII’s PDPM is optimized to manage models including product components, relationships, and other associated information. Product data, including solid geometric information, feature information, engineering information (tolerance, material, finish, etc.), and process [6], an object- information, etc., is managed by OSCAR oriented database management system, developed by AI of Zhejiang University. OSCAR not only supports Institute EXPRESS schema [7] and STEP SDAI [8] (Standard Data Access Interface), but also acts as an engineering data management system of the CAD/CAPP/CAM integrated system. The uniqueness of product data in OSCAR ensures the correctness of the full associativity of all models. DEI (Data Exchange Interface) may exporthmport product data to/from other CAD/CAM systems. To support concurrent engineering, a CAD system must be open and flexible enough to exchange product data with other CAD systems or CAE, CAPP, CAM systems. The standard STEP [9] is 6 the first international standard undertaken by the International Standard Organization (ISO), that enables the capture of information comprising a computerized product models in a neutral form without bss of completeness and integrity throughout the whole life cyde of a product [l0]. One of the most important points of the STEP development is the formal object-oriented and computer processable language EXPRESS, which is used to define the standard in an unique is a trend that most and unambiguous way. We believe that it of CAD/CAM system developers will make their systems support STEP standard in future. For modeling according the STEP product model, it is certain complete that ZD-MCADII supports STEP. As a result, a STEP data translator is not necessary any more, ZD-MCADII is able to generate STEP neutral file for a product or retrieve a STEP neutral file toform internal STEP product model directly. Namely, ZD- MCADII can deal with STEP product data without any translation. As well as STEP, DEI also supports other IS0 or industry standard, such as IGES, SET, DWG, DXF, etc. DEI is so expandable that is can support any other standard now or a new translator of later, the only thing you must do is just add that standard to DEI. Another aspect of ZD-MCADII’s openness is that it provides user application development interface. This interface contains two component: macro language programming interface and C/C++ programming interface. User can take .advantage of these two interfaces to develop hisher own specific application, such as piping design system, mold design system, cabling design system, or applications cgnjuncted with other CAE/CAPP/CAM systems. ZD- MCADII’s macro language is a Parametric Programming (PPL), developed by AI Institute of Zhejiang Univ. Language also, for writing user command to automate tedious, repetitive operatqr activities. A user command can be a single 7 command or a wries o? several interactive graphic commands which appear to the user as a single command. A user command written in PPL is contained in an ASCII file, and it can be compiled with C/C++. A user can use the PPL to: ?a Automate repetitive tasks ?Combine several commands from the screen menu to operate as though they were a single command ?Modify the user interface to the screen menu commands’for an application. C/C t-t pmgramming develop toolkit includes several libraries, such as geometry model, graphic display, user so on. interaction, database, part management, and so on. IV. FLOW OF DESIGN INFORMATION IN ZD-MCADII In ZD-MCADII, user starts a design from 3D feature modeling, unlike traditional 2D drawing design. Fig. 3 illustrates the flow of design information in ZD-MCADII. A prbduct’s drawing will be generated automatically through projecting a 3D part model or 3D assembly model simply. Furthermore, the drawing will keep The full association with 8 its 3D model, and when 3D model be changed, the associated drawings or assemblies will be updated automatically to reflect changes made in 3D model. With maintaining the consistency and integrity of a product, a time-consuming design task will become very convenient and more instinctive. In fact, 70-80 per cent of the mechanical design be taken advantage of 3D modeling technology in the developed and the number has a very quick increase aver the countries, world today. Part’s Engineering Design (PED) is to define non-geometric information such as material, tolerance, finish, hot process of surface, etc. After generating the part model, user can enter Drawing Design Module (DDM) to produce the detail drawings for that part, or enter Assembly Design Module (ADM) to construct and manage ultra- large, complex assemblies with an unlimited number of components, or enter Process Design Module (PDM) to. form the process model delivered to GS-CAPP, which is a process planning system , based on knowledge base and expert system techniques. 9 When the process model leaving the Process Planning Module (PPM), it will be converted into manufacturing model accepted by GS-CAM, a CAM system with the functions of automated NC programming, interference detection and handling, machining process simulation, and the general post- processing. V. FLOW OF CONTROL IN ZD-MCADII Fig. 4 illustrates the flow of control in ZD-MCADII. Components of the,diagram are: ?User input consists of raw commands and actions and comes from the user input (through the keyboard or using the mouse) or files containing command scripts written in PPL. ?UI event handler processes the user input, and divides these input into three components: mouse event, keyboard event and PPL program, then delivers these information to three handlers (mouse event 10 handler, keyboara event handler and PPL handler) respectively. ?Mouse event handler is designed to get the user input data from mouse’s movement or the mouse’s clickingevent, then transmits these mouse data to the Com- mands processor. ?Keyboard event handler is mainly to gather the keyboard input entered by user, then delivers the keyboard data to the Commands processor too. To fit in any situations, ZD-MCADII can run correctly in the situation that user only has a keyboard and no mouse, vice via. ?PPL handler processes the user-written PPL programs, and translates the PPL into the corresponding C/C++ calls provided by the Kernel of ZD-MCADII. ?Commands processor, developed by two UNIX toolkits: LEX and YACC, tries to understand the mouse data and keyboard data, and these input data will be translated into Kernel’s C/C++ calls. ?Kernel of ZD-MCADII contains several important 30 Geometric Modeling Kit, components including Part Design Kit (Feature Modeling), Assembly Design Kit, Drawing Design Kit, Graphic Display Kit, Product Management Kit (OODB), and Product Data Import/Export Kit, etc. VI. CONCLUSION ZD-MCADII has already been implemented in UNIX WMotif environment on Sun SPARC workstation. We choose is more C/C++ to develop this system. The amount of source than 450,000 lines. The system has also been integrated with our CAPP system (GS-CAPP) and CAM system (GS-CAM) ZD- MCADII in the integrated system GS-ICCC successfully. also serves as a platform for developing future intelligent integrated CAD/CAM system with concurrent engineering design capability. Ⅶ. REFERENCES [1] J.J., Shah, “Assessment of Features rechnology,” CAD, vol. 23, 11 no. 5, 1991, pp. 331-343. [2] Li Hailong, “The Research of Feature-Based Parametric for CIMS,” MS Dissertation, Zhejiang M,odeiing System University, 1995. [3] Li Hailong, Dong Jinxiang, Tan Mengen, “Feature-Based Modeling System for Mechanical Product Design,” in The Fourth international Conference on CAWCG, Wuhan, China, 1995, pp. 508-513. [4] Ge Jianxin, “The Research and Implementation of the New Ph. D. Dissertation, Generation of CAD System,” Zhejiang University, 1993. 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