lect13-standard for data exch

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    Standards for CAD Data Exchange

    KP3213 CAD/CAM

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    ProductDesign(CAD)

    Engineeringand Analysis

    (CAE)

    CustomerRequirements

    ProductDatabases

    ManufacturingDatabases

    MaterialsPlanning Procurement

    Installationand

    DistributionFabrication, Assembly & Test Operations

    ProductInformation

    Management

    Product Design

    ManufacturingEngineering

    Supply Management

    Customer

    Suppliers

    Marketing

    ProcessPlanning

    Neutral I/F

    Neutral I/F

    Product Data ManagementCAD data is used throughout

    the organization

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    The Supply Chain

    Suppliers Customers

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    The Virtual Enterprise

    Most products require the coordinated effort of a

    large number of companies in the supply chain

    The supply chain can be thought of as a virtualenterprise

    Product data and other information must be

    shared between the participating companies

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    Virtual Enterprise

    Suppliers

    Customers

    Virtual

    Enterprise

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    Typical Situation

    Major company

    uses CATIA

    Major supplier

    uses I-DEAS

    Small supplieruses AutoCAD

    Small supplier

    uses Solid Edge

    Partner uses

    Unigraphics

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    The Problem

    Every CAD system uses its own proprietary data

    format

    Design data must be converted from one formatto the other

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    Direct Translation between CAD

    Systems Need a translator from

    every CAD package to

    every other

    For 4 CAD packages,need 6 translators

    For 6 CAD packages,

    need 16 translators!

    I-DEAS Unigraphics

    Pro/EngineerCATIA

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    Data Exchange Standards

    To address the problem, many standards for CAD

    data exchange have been developed

    CAD systems can import and export to many ofthese standard formats

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    Interfaces

    CAD/CAD CAD/CAM

    Standardization Organization

    National & European International ISO

    IGES

    PDDI

    SET

    VDA/FS

    CAD*I

    CIM-OSA

    EDIF

    PDES ANSI (USA)

    AFNOR (France)

    DIN (Germany)

    ESPRIT (EEC)

    ESPRIT (EEC)

    Product Data Structure

    STEP

    ( A full data model)

    USA Electronics Industry ???

    Evolution of Data Standards

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    Current Situation

    Translation using IGES is unreliable

    geometry is corrupted

    much cleanup required after translation Translation using STEP is not widespread

    STEP translators only recently available

    Existing translators lose information

    parametrics and constraints features and history trees

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    Short-term Solutions

    To avoid data translation problems, many

    companies have standardized on a single CAD

    system Ford

    all suppliers must use I-DEAS

    Chrysler

    all suppliers must use CATIA General Motors

    all suppliers must use Unigraphics

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    New Problem for Suppliers

    To deal with all three automakers, you must

    support I-DEAS, Unigraphics and CATIA!

    For small companies, this is very difficult

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    A Better Solution

    A better solution is development of reliable data

    exchange standards, using a neutral interface

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    CAD 1 CAD 2 CAE 1 CAE 2

    Neutral Interface

    CAPP PP&C CAM CAQ

    Neutral Interface

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    Requirements of an Interface

    The interface must be capable of handling all

    manufacturing data

    There should be no information loss (maintain thesemantics during conversion)

    The system must be efficient to be capable of

    handling the realtime requirements of

    manufacturing The system should be open-ended to permit

    extensions or contractions

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    Requirements Continued

    The system should be adaptable to other

    standards

    The system must be independent of the computerand architecture used

    It must be possible to form application-oriented

    subsets of the standard to reduce costs

    The interface must be upward and downwardcompatible in a hierarchical control structure.

    Test procedures must be provided to verify

    effectivety.

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    Initial Graphics Exchange

    Specification (IGES) Formatted ASCII file format

    Supports many 2D and 3D CAD entities

    Has gone through several versions since 1980 Widely supported

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    Problems with IGES

    Many incompatible flavours

    Unreliable translation, particularly for complex

    geometry No formal information modelling basis

    Insufficient support for conformance testing

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    STEP

    (Standard for the Exchange of Product Model Data)

    Uses a formal model for data exchange

    Information is modelled using the EXPRESS language

    EXPRESS has elements of Pascal, C, and other languages It contains constructs for defining data types and structures,

    but not for processing data

    EXPRESS describes geometry and other information in a

    standard, unambiguous way

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    STEP Architecture

    Layer 1: Implementation methods

    (EXPRESS)

    Physical files

    Layer 2: Resource information models

    Layer 3: Application protocols

    Conforman

    cetesting

    &t

    est

    suites

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    Classes of STEP Parts

    Introductory

    Description methods

    Implementation methods Conformance testing methodology and framework

    Integrated resources

    Application protocols

    Abstract test suites

    Application interpreted constructs

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    Status of STEP

    STEP has been under development for many

    years, and will continue for many more

    Over a dozen STEP parts have been approved asinternational standards

    Many others are under development

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    Other Standards

    Standards for technical documents

    Standards for images

    Internet and Web standards

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    Continuous Acquisition and Life-

    cycle Support (CALS) Developed by US Department of Defense

    Prescribes formats for storage and exchange of

    technical data Technical publications an important focus

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    Important CALS Standards

    Standard Generalized Markup Language (SGML)

    document description language

    separates content from structure (formatting) uses tags to define headings, sections, chapters, etc.

    HTML is based on SGML

    Computer Graphics Metafile (CGM)

    vector file format for illustrations and drawings

    IGES

    also used for illustrations

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    Common Formats for Bitmap Images

    Standards

    Joint Photographic Expert Group (JPEG)

    Proprietary Graphics Interchange Format (GIF)

    Windows bitmap format (BMP)

    Zsoft file format (PCX)

    Tagged Image File Format (TIFF/TIF)

    Targa file format (TGA)

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    Web and Internet Standards

    Hypertext Markup Language (HTML)

    used to describe web pages

    based on SGML Virtual Reality Modelling Language (VRML)

    standard for description of 3D interactive environments

    and worlds

    downloaded and displayed in a web browser

    well suited to sharing of CAD data

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    Other CAD File Formats

    DXF

    de facto standard published by AutoDesk (AutoCAD)

    STL 3D file format used as input for Stereolithography

    SAT

    solid model file format used by ACIS-based CAD

    systems