Product Data Interfaces in CAD/CAM Applications : Design, Implementation and Experiences

Interest in product data exchange and interfaces in the CAD/CAM area is steadi­ ly growing. The rapidly increasing graphics applications in engineering and sci­ ence has led to a great variety of heterogeneous hardware and software products. This has become a major obstacle in the progress of systems integration. To improve this situation CAD/CAM users have called for specification and imple­ mentation of standardized product data interfaces. These needs resulted in the definition of preliminary standards in this area. Since 1975 activities have been concentrated on developing standards for three major areas: - computer graphics, - sculptured surfaces, and - data exchange for engineering drawings. The Graphical Kernel System (GKS) has been accepted as an international standard for graphics programming in 1984, Y14.26M (IGES) was adopted as an American Standard in 1981 and the VDA Surface Interface (VDAFS) has been accepted by the German National Standardization Institute (DIN NAM 96.4). Although considerable progress has been achieved, the complexity of the subject and the dynamics of the CAD/CAM-development still calls for more generality and compatibility of the interfaces. This has resulted in an inter­ national discussion on further improvements of the standards. The major goal of this book is to bring together the different views and experiences in industry and university in the area of Product Data Interfaces, thereby contributing to the ongoing work in improving the state of the art.

1 Introduction ― Reference Models, Interfaces, Integration Issues.- 1.1 Goals in the Application of CAD Interfaces.- 1.1.1 Global Objectives.- 1.1.1.1 Introduction.- 1.1.1.2 Ranges of Application for the CAD Interfaces.- 1.1.1.3 Global Objectives for the Application of Computer Assisted Systems and of CAD Interfaces.- 1.1.2 Application of CAD Interfaces in Computer Assisted Processes.- 1.1.2.1 Product Concept.- 1.1.2.2 Construction, Calculation, Testing.- 1.1.2.3 Manufacturing Engineering.- 1.1.2.4 Assessment in Relation to Objectives.- 1.1.3 Current and Future Developments in CAD Interfaces from the Application Standpoint.- 1.1.4 References.- 1.2 Interfaces and Data Transfer Formats in Computer Graphics Systems.- 1.2.1 Introduction.- 1.2.2 Data Interfaces.- 1.2.3 The Standards for Graphics Programming (GKS,D-GKS, GKS Output Level 3, GSPC Core and PHIGS) 16.- 1.2.4 Graphics Metafiles (GKSM and VDM).- 1.2.5 Device and Workstation Interfaces (VDI and WSI).- 1.2.6 Videotex Files (NAPLPS and CEPT/VPLP).- 1.2.7 Product Data Transfer Formats (IGES, VDAFS, TAP, EDIF).- 1.2.8 Graphics in the Processing of Text Documents Which Include Graphics (CLPT).- 1.2.9 Presentation Graphics Layer on Top of GKS.- 1.2.10 GKS in a Network Environment.- 1.2.11 References.- 1.3 CAD/CAM: Integration in the Automobile Industry.- 1.3.1 Introduction.- 1.3.2 Demands on and Requirements of an Integrated Concept.- 1.3.3 The CAD/CAM Process Chain in Automobile Manufacturing.- 1.3.3.1 Product Model and Data Management.- 1.3.3.2 Information and Communication in the Process Chain.- 1.3.4 System Engineering Aspects of an Integrated CAD/CAM Concept.- 1.3.4.1 A Possible Hardware Architecture.- 1.3.4.2 Network Architecture.- 1.3.4.3 Software Architecture.- 1.4 Interfaces for CAD Applications.- 1.4.1 Introduction.- 1.4.2 CAD Systems.- 1.4.3 Interface Possibilities.- 1.4.4 Communication.- 1.4.5 Interface Requirements.- 1.4.6 Interface Standards.- 1.4.7 Data Base Interface.- 1.4.8 Interface Implementations.- 1.4.9 Conclusion.- 2 Graphics Systems ― Graphical Standards ― GKS.- 2.1 Graphical Standards.- 2.1.1 Introduction.- 2.1.2 The Graphical Kernel System ― GKS.- 2.1.3 GKS and Other Graphics Standards.- 2.1.4 Language Bindings.- 2.1.5D-GKS 77.- 2.1.6 PHIGS.- 2.1.7 Metafiles and Device Interfaces.- 2.1.8 Certification, Formal Specification, Registration.- 2.1.9 Graphics and CAD.- 2.1.10 Graphics in Documents.- 2.1.11 Outlook.- 2.1.12 References.- 2.2 GKS and Intelligent Terminals.- 2.2.1 Introduction.- 2.2.2 Intelligence of Terminals.- 2.2.3 GKS Driver Interfaces.- 2.2.4 Utilization of Local Intelligence by GKS.- 2.2.5 Problems: GKS versus Intelligent Terminals.- 2.2.6 Minimal GKS.- 2.2.7 Distribution of GKS in Kernel, Driver, Device and Utilities.- 2.2.8 References.- 2.3 Tektronix PLOT 10 GKS ― Tailored for Customer’s Needs.- 2.3.1 Introduction.- 2.3.2 Dynamic Memory Management.- 2.3.3 A New View of Workstations.- 2.3.4 A Standards Solution to Graphics Problems.- 2.3.5 Standardization Means Device Independence.- 2.4 Common Graphics Manager ― Design Concepts.- 2.4.1 Introduction.- 2.4.2 Concepts of GKS.- 2.4.3 Further Standards.- 2.4.4 Design Concepts.- 2.4.5 Design Realization.- 2.4.6 Conclusions.- 2.4.7 Appendix.- 2.4.8 References.- 2.5 GKSGRAL ― Software and Hardware Realizations of the Graphical Kernel System.- 2.5.1 Introduction.- 2.5.2 The GKSGRAL System Structure.- 2.5.2.1 The GKSGRAL Kernel.- 2.5.2.2 The GKSGRAL Workstation Interface.- 2.5.2.3 The GKSGRAL Workstation Layer.- 2.5.2.4 The GKSGRAL Device Interface.- 2.5.2.5 The GKSGRAL Device Driver Layer.- 2.5.3 GKSGRAL Interfaces’.- 2.5.3.1 Language Interfaces.- 2.5.3.2 Metafile Interfaces.- 2.5.3.3 Graphical Device Interfaces.- 2.5.3.4 Symbol Interfaces.- 2.5.4 The GKSGRAL Workstation Handler.- 2.5.5 The GKSGRAL Metafile Handler.- 2.5.6 The GKSGRAL Segment Storage Handler.- 2.5.6.1 Purpose.- 2.5.6.2 The Storage Module Interface.- 2.5.6.3 Storage Module Structure.- 2.5.6.4 Integration of the WISS into GKSGRAL.- 2.5.7 GKSGRAL Input.- 2.5.8 GKSGRAL Configuration Possibilities.- 2.5.9 GKSGRAL Installations.- 2.5.10 GKSGRAL Device Drivers.- 2.5.11 The GKSGRAL Engine.- 2.5.11.1 Functionality.- 2.5.11.2 Advantages.- 2.5.11.3 Software/Firmware.- 2.5.11.4 Hardware.- 2.5.11.5 Extensions.- 2.5.12 References.- 3 Initial Graphics Exchange Specifications ― Implementation, Experience.- 3.1 Product Data Exchange; Design and Implementation of IGES Processors.- 3.1.1 Abstract.- 3.1.2 Introduction.- 3.1.3 IGES: Overview.- 3.1.4 IGES: Intrinsic Problems.- 3.1.4.1 IGES Entity Set.- 3.1.4.2 IGES Format.- 3.1.4.3 IGES Translators.- 3.1.5 Design of an IGES Translator.- 3.1.5.1 Internal IGES Files (IIF).- 3.1.5.2 IIF Interface.- 3.1.5.3 Functions of the EDIT Phase.- 3.1.5.4 Functions of the EXCHANGE Phase.- 3.1.6 Summary.- 3.1.7 References.- 3.2 Experience Gained Using the IGES Interface for CAD/CAM Data Transfer.- 3.2.1 Introduction.- 3.2.1.1 CAE Use in Product Development.- 3.2.2 Areas of Applications of the IGES Interface at BMW.- 3.2.2.1 Data Exchange Between CAD Systems.- 3.2.2.2 Data Exchange Between CAD and CAM Systems.- 3.2.2.3 Data Exchange Between CAD and Calculation Systems.- 3.2.3 Basic Problems in the Field of CAD Data Transfer.- 3.2.3.1 CAD System Variety.- 3.2.3.2 IGES Interface Definitions.- 3.2.3.3 IGES Processors.- 3.2.3.4 Transfer Media.- 3.2.4 Example of Practical Use.- 3.2.5 Verification of IGES Processors from the User’s Point of View.- 3.2.6 Summary.- 3.2.7 References.- 4 VDAFS ― Functionalities, Approximation Methods, Implementation, Experience.- 4.1 VDAFS ― A Pragmatic Interface for the Exchange of Sculptured Surface Data.- 4.1.1 History.- 4.1.2 Pragmatic Goals.- 4.1.2.1 Geometrical Elements.- 4.1.2.2 General Properties.- 4.1.2.3 Remarks.- 4.1.3 Example.- 4.1.4 Syntax and Rules.- 4.1.4.1 General Rules.- 4.1.4.2 Geometrical Elements.- 4.1.4.3 Non-Geometrical Elements.- 4.1.5 Really Pragmatic?.- 4.1.5.1 Why Not IGES?.- 4.1.5.2 VDAFS-State of the Art.- 4.1.6 Further Developments.- 4.1.7 References.- 4.2 Approximation Methods Used in the Exchange of Geometric Information via the VDA/VDMA Surface Interface 150.- 4.2.1 Introduction.- 4.2.2 The VDA-VDMA Surface Interface.- 4.2.3 Approximation Methods.- 4.2.3.1 Goals.- 4.2.3.2 Degree Reduction.- 4.2.3.3 Degree Elevation.- 4.2.3.4 Results.- 4.2.4 Conclusions.- 4.2.5 References.- 4.3 A Tentative Implementation of VDAFS.- 4.3.1 A Short Description of VDAFS.- 4.3.2 Implementation.- 4.3.3 Usage.- 4.3.4 Problems.- 4.3.5 References.- 4.4 Implementation of a VDA Interface in the CAD System STRIM 100.- 4.4.1 Abstract.- 4.4.2 Introduction.- 4.4.3 STRIM: the Product 167.- 4.4.4 Basic Concepts of the Interface.- 4.4.5 VDA Output.- 4.4.6 VDA Input.- 4.4.6.1 Check.- 4.4.6.2 Contents.- 4.4.6.3 Transfer.- 4.4.7 Preliminary Experience.- 4.4.8 Conclusion.- 4.4.9 References.- 4.5 The Implementation of the VDAFS Geometric Data Interface on Computervision’s CDS 4000 CAD/CAM System.- 4.5.1 Introduction.- 4.5.2 “What is the VDAFS Interface?”.- 4.5.2.1 Geometric Data Interfaces.- 4.5.2.2 General Description of VDAFS.- 4.5.2.3 Objectives of VDAFS.- 4.5.2.4 Comparison with Other Geometric Data Interfaces.- 4.5.3 Implementation of the VDAFS Interface on the CDS 4000.- 4.5.3.1 PUT VDAFS-Creation of the VDAFS File.- 4.5.3.2 GET VDAFS ― Creation of the CADDS 4X Part from the VDAFS File.- 4.5.3.3 Correspondence between CADDS 4 X Entities and VDAFS Records.- 4.5.3.4 Implementation Philosophy.- 4.5.4 Future Developments.- 4.6 Experience with VDAFS.- 4.6.1 Introduction.- 4.6.2 VDA-Working Group “Test”.- 4.6.3 VDA-Interface Test.- 4.6.4 VDAFS-Interface Problems Resulting from CAD/CAM Systems.- 4.6.5 VDAFS ― Disadvantages.- 4.6.6 VDAFS ― Extensions.- 4.6.7 Outlook.- 4.6.8 References.- 5 Specification and Validation.- 5.1 Specification of Interfaces: A Case Study of Data Exchange Languages.- 5.1.1 Introduction.- 5.1.2 The First Part of the Case Study.- 5.1.3 The Types of CADE.- 5.1.4 The Types of CADA.- 5.1.5 The Semantics of the Data Transfer.- 5.1.6 The Second Part of the Case Study.- 5.1.7 A Concrete Interface Language.- 5.1.8 A Glance at the Development of Programs.- 5.1.9 References.- 5.1.10 Appendix: Pascal Implementations.- 5.2 Validation of Graphics Systems.- 5.2.1 Introduction.- 5.2.2 Goals of Certification.- 5.2.3 Software Validation Techniques.- 5.2.4 The Interfaces for Testing.- 5.2.4.1 Testing at the Application Interface.- 5.2.4.2 Testing at the Operator Interface.- 5.2.4.3 Testing at the Device Interface.- 5.2.4.4 Configuring a Reference System.- 5.2.5 Conclusions and Further Planning.- 5.2.6 References.- 5.3 Testing and Validation of IGES Processors.- 5.3.1 Introduction.- 5.3.2 Basic IGES Concepts.- 5.3.3 General Test Criteria.- 5.3.3.1 Entity Set.- 5.3.3.2 Exchangeability.- 5.3.3.3 Functionality.- 5.3.3.4 Graphical Representation.- 5.3.3.5 Accuracy.- 5.3.3.6 Syntactical Correctness.- 5.3.3.7 Software Quality.- 5.3.4 Test of IGES Processors.- 5.3.4.1 Test Methods.- 5.3.4.2 IGES Test Library.- 5.3.4.3 Test Data.- 5.3.5 Validation of Test Results.- 5.3.5.1 Comparing Pictures.- 5.3.5.2 Comparing Data Bases.- 5.3.5.3 Comparing Operations.- 5.3.5.4 Handchecking.- 5.3.5.5 Software Tools.- 5.3.6 IGES File Analysis System.- 5.3.7 Test Concept and Future Outlook.- 5.3.8 References.- 6 Outlook.- 6.1 Progress in the Development of CAD/CAM Interfaces for Transfer of Product Definition Data.- 6.1.1 Transfer of Product Definition Data.- 6.1.1.1 The Necessity for Transfer of Product Definition Data.- 6.1.1.2 Product Definition Data as an Internal Computer Model.- 6.1.1.3 Principle of Operation and Status of Implementation of CAD/CAM Interfaces.- 6.1.2 CAD/CAM Interface Development.- 6.1.2.1 Requirements of a CAD/CAM Interface from the Application Viewpoint.- 6.1.2.2 General Requirements for a CAD/CAM Interface Concept.- 6.1.3 Status of Standardization of an Interface for Transfer of Product Definition Data in Germany.- 6.1.4 References.- Contributors.