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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