Fundamentals of CAD

7/29/2019 Fundamentals of CAD

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SystemsFundamentals of

Computer Aided

Design

Product realization systems. Review

of part specification and CAD

Design drafting

Design interpretation

Inspection and measurement

Architecture of CAD

CAD hardware and software Geometric modeling

CAD data exchange

CAD system examples


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Evolution/Realization of a Product

Computers in The Engineering Office

The type of computer can be used to assistengineers job function.

The fundamentals of computing applied toengineering and the hardware available forcarrying out engineering tasks will be

examind.Computer facilities and services can bedivided into 2 areas : hardware andsoftware


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Computers are classified asanalog or digital.

Analog computers aregenerally used formathematical problemsolving. (control electronic,mechanical equipment)

Digital computers count by

digits in distinct steps.(electric wall clock)

Polish analogue computer ELWAT

Historical Background of Computing

(1830s) C. Babbage developedthe idea of a mechanical digitalcomputer. (undertake laboriouscalculations ; store the resultsfor further use)

(1904) A. Fleming invented thefirst diode.(allow current to

flow in one direction)L. De Forest devised the triodevalve. (control the flow ofcurrent)

Babbage'sDifference Engine
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Historical Background of Computing

(1940s) Thermionic valves wasused in the first electroniccomputers.(filling largerooms; generating largeamounts of heat)(1947) The first transistorwas developed at Bell Lab.(valve computer !)2nd generation computer; thetransistor was introduced.3rd generation computer;

based on small-scaleintegrated circuits.(early1960s)4th generation computer;based on integrated circuit.

Historical Background ofComputing

4th generation computer technologyreduces in size of computers

increases in performance of large

computers.are becoming cheaper year by year.
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SORTED HISTORIC COMPUTERS LIST 1. Pre-1960's Mainframes (Vacuum Tubes)

2. Transistorized Mainframes3. Early Supercomputers (1964 - 1979)4. Supercomputers (1980 - 1990)5. Supercomputers (1991 - present)6. Mainframes (Integrated Circuits -- No Microprocessor)7. Embedded Computers and Military-Specific Computers8. Minicomputers (Transistorized/discrete)9. Minicomputers (Integrated Circuits -- No Microprocessor)10. Post-Microcomputer Mainframes and "Super-Minis" (1980 - 1991)11. Microcomputers (1974 - 1980)12. Microcomputers (1981 - 1984)13. LISP Machines and related workstations (1978 - 1987)

14. Desktop Workstations and Enterprise systems15. Personal Computers (1985 - 1991) [Industry Consolidation]16. Personal Computers (1992 - present)

Basic Architecture of a CAD System Major Classes:

Main frame

Mini computer

Workstation

Microcomputer

Based.

Application Areas:

Mechanical

Architectural Construction

Circuit design

Chip design

Cost:

High end

Low end


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Hardware & Software

There are four major functions whichmust be addressed when dealing withthe application of a computer system.

Input

Output

Processing Storage

CAD/CAMHardware

Mainframe based CAD

System Organization

(a) Basic elements

(b) Workstation

elements


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CAD/CAM

Hardware

Input-OutputDevices

Hardware for CAD Systems

Hardware

is used to describe the physicalequipment (electronic circuitry)

and its peripherals (mouse, printer).


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Two types of computer hardware exist:

Hardware in office environment ; is in thedesign/manufacturing office

Hardware in shopfloor; is used to control

machinery and processes.

CRT and LCD Keyboard Mouse Tablet button/dial

boxes light pen touch screen

track balls joy stick punched cards CMMs Scanners 3D scanners

Device Resolution Speed Cost Fatigue

Mouse Medium High Low Medium

Keyboard Exact Low Low Medium

Tablet High High High Low

PositionJoystick

Medium High Low Low

VelocityJoystick

High Medium Low Low

Light pen Low High Low High



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Only about 50 years ago, ittook a whole room to hold acomputer. Now, handheld unitslike the Blackberry are thesize of a couple of decks ofcards. Whats next?

How about a PC keyboard,display and all that you carryaround in pocket like a handfulof pens?

Future hardware input devices include,

virtual reality gloves

voice

scanned input and recognition

vision systems

Future hardware input devices include

Previous output devices include

Text printers

Graphics printers

Plotters

CRT

Rapid prototyping

Virtual reality vision systems


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P-ISM

One gadget package looks like aset of pens.Its got a cell phone with a

handwriting function, aprojector that throws akeyboard onto your desk,another that beams out adisplay, a camera and scannerand a personal ID device with acash pass function.

Future hardware input devices include,


Two types of digital computers :(mainframe & minicomputer)

Mainframe ; large installation , fair-sizedroom (temperature & humiditycontrolled), only accessible to large

company, data processing applicationMinicomputers; smaller, less powerfullsimpler than a mainframe, for smallcompanies,


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Mainframe is capable ofallowing greater number ofpeople to use the computerat the same time. (=Multi-user systems=)

The facilities of typicalmainframe installation

Processing (execute the programs)Storage

Hard copy service (print / plot)


Text terminal

Modem

Graphic terminal Personel Computer

Workstation

Mainframe

Installation

Public telephone line

Local area network


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The first computer configuration

In 1963 Sketchpad

was invented

by Sutherland in MIT.

It ran on the Lincoln TX-2

computer.

Computer

Keyboard

Light pen

Cathode ray tube

(CRT)


Sketchpadcomputer programwritten by IvanSutherland1963 his PhD thesis.be the ancestor ofmodern computer-aideddrafting (CAD) ,development ofcomputer graphics ingeneral.
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computer graphics be utilized forartistic and technical purposesa novel method of human-computerinteraction.utilize a complete graphical userinterface.used an x-y point plotter

display as well as thelight pen.


organized its geometric data pioneeredthe use of "objects" and "instances" incomputing and pointed forward to objectoriented programming.ran jobs in batch job mode only,

using punch cards or magnetic tape.
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Typical PC configuration

Computers in The Engineering OfficePCs & Workstations are becoming the most popularplatforms for CAE applications.PC / Workstation is designed for a single user andaccessible over a network.Processor (CPU)Data storage system (tape drive, hard(fixed) disk, soft(floppy) disk, optical disk (CD-ROM, DVD-ROM), flashmemory)Remote-harddiskMonitorInput devices (keyboard, mouse,

digitizer, trackball, scanner)Output devices (printer, plotter)


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CAD WorkstationsMany CAD programs need a lot of computingpower and most CAD systems use good-quality graphics screens to display drawings.One posible configuration consists of aminicomputer with 4 graphics terminal, aprinter and a plotter.

32-Bit CPULarge

Memory

High-resoulution

Graphics display

Printer

Plotter

Mouse

Digitizer

Large disks

Keyboard

Link to other

computers


CAD stations can be linked eitherdirectly or through a local area network(LAN)to the manufacturing orproduction,or,

with numerical control (NC)

equipment to program to NC machines inmanufacturing operations or in robotics.


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Computers in The Engineering OfficeSupercomputer tends to become tomorrow's normalcomputer.

In the 1970s mostsupercomputers werededicated to running a vectorprocessor,Mid-1980s saw machineswith a modest number of

vector processorsworking in parallelbecome the standard.

supercomputer

Networked

supercomputing


In 1990s, attention turned from vector processors tomassive parallel processing systems with thousands of"ordinary" CPUs, some being off the shelf units and

others being custom designs.Parallel designs are based onRISC microprocessors, such as

the PowerPC or PA-RISC, andmost modern supercomputersare now highly-tuned computerclusters using commodityprocessors combined withcustom interconnects.
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INPUT (POINTING) DEVICES

CAE applications make use of computergraphics then one of the most importanthardware facilities which provides aninterface between the engineer and thesoftware is the graphics pointing device.Mouse Digitizer (tablet)Light pen Joystick

Scanner


MouseMovement of mouse over a flat surfacecauses a corresponding movement of cross-hair on the graphics screen.

2-button

3-buttoninfrared

opticwireless


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Principles of mouse operationDigitizer disks have an arrangement of slots.

As they rotate an infrared ligt beam is cut by thematerial between the slots. It produces

electrical pulses.

Computers in The Engineering OfficeDigitizer & TabletTablet consists of a flat surface over. The cursorcan have any number of function buttons which areinterpreted by the software.Electromagneticcommunication betweena coil in the puck andan accurately arrangedgrid of wires in the tablet.


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Digitizer can be used for three tasks :As a pointing device to the screenAs a menu selection deviceAs a means of digitizing manuallyproduced drawings.


Digitizing Three Dimensions

3D digitizer system fromrecords x, y and z coordinatesof an object by touching itssurfaces with a pen.It measures the tip position in3D space and outputs directlyto popular CAD and graphicsprograms


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JoystickIt has been used for many years as agraphical input device for CAE softwarebut is used very rarely nowadays.

One major advantageof a joystick is thesimple construction.


TrackballIt is one of the oldest input devices used onmany large mainframe-based CAD systems.

It consists of a ball nested

in a holder, and from 1 to 3buttons for enteringcoordinate data into thesystem


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Light PenIt is the oldest of all pointing devices andwas used with the very first CADD systems.

It is very low-cost deviceand, simple to operate.


Scanner

It is an input device used for convertingdrawing created traditional tools to a CADdrawing.

Vector image Raster image


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OUTPUT DEVICES

The result of CAE task is always someform of human-readable output.

Report

Drawing

Parts list

Stock inventory


Printer

It is used to get text output anddocuments.

Text-only printers

Dot matrix printers


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Daisy wheel printerText-only printersimilar to a manualtypewriter.plastic or metal hub withspokes like an old-fashioned wagon wheelminus the outer rim.

At the end of each spokeis the carved image of atype character.


Line printer.form of high speed printer inwhich one line of type isprinted at a time.

They are mostly associatedwith the early days ofcomputing, but the technologyis still in use.

Print speeds of 600 to 1200lines-per-minute(approximately 10 to 20 pagesper minute) were common.
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Dot matrix printer

It can reproduce text and graphics.

9 / 24 pin dot matrix printer


Dot matrix printer


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Other printers

ink jet printer

laser printer

thermal printer


PlottersThey are used for larger drawings such as

A3 or greater.Choosing a plotter depends on the space considerations in the design

office

the size of paper to be used speed of reproduction mode of operation the variety of different line widths or

colours


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Pen plotters

Flat bed plotters

Drum type plotters

Electrostatic plotters


Flat bed plotter (for small paper)Single-sheet form is placed on the flat bed.Pens are selected from a carousel / bankThe pen in use is moved over the paper.


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Drum PlotterThe paper is suppliedon a roll.The pens are moved inone direction along thelength of the roller ona gantry.The roller constructionmakes the plottermore compact.


Electrostatic PlotterIt is more common.It operates on a similar principle of laserprinter.

It can produce largequantities of drawingwithout a paper change.


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Software is the computer programwhich is run and executed by thecomputer.

Software is expected to perform manytasks with more speed, and accuracythan a person.

Software will not perform a taskbetter.

Software for CAD Systems

CAD SoftwareGeometrical model

2D/3DExact or faceted withplanar polygonsMass properties

EditingParametric

Object OrganizationNamed ObjectsLayersPart libraries

Drawing OutputDrafting module

Analysis ModuleFinite ElementsPlastic FlowKinematics/CollisionsDynamics

Importing/ExportingSurface formats: IGES,DXF, CDLSolid Formats:

PDES/STEP, ACIS, SATFiles for systems such as

NASTRANCan be linked to a userwritten program

RenderingHidden lineShaded ImageRay TracingReal Time Rotations

SoftwareOperating SystemUnix, Windows, Apple,


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CADD Software Structure

Addition &modification

Geometricdatabase

Graphicaldisplay ofdrawing ordesign

Hardcopyoutput

input

output outputDatabasecontains 2D or

3D geometry ofthe drawing.

(mathematicalmodel)

Userinterface

CAD/CAM learning curve


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Software Selection

The size of the company and the amount ofinvestment capital available will be one ofthe main deciding factors but there aremany other questions to be considered:

Mainframe or PC/workstation platform? Two dimensions or three? Lines, surfaces

or solids?

Other analysis tools needed? Will theability to transfer the geometry to thesemodelling and analysis systems be needed?

Software Selection

Software Selection ... Compatibility with other systems needed?

How good is the maintenance and supportfrom the suppliers?

How much, how good and how long is thetraining?

How easy is it to expand the system?


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Software Trends

Software changes more slowly than hardware:bounded by basic principles.

Software bottleneck

Integration and automation of the developmentprocess

Solid modeling seems to be the key technique

to automate and integrate CAD/CAM.

Sales of

CAD/CAM system

components


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Commercial CAD/CAM Software

Software for CAD SystemsAutoCAD is PCbased CAD software products (late 1982).

Mechanical Desktop is an integrated package of advanced 3Dmodeling tools.

Pro/ENGINEER or Pro/E (3D) feature-based, solids modelingsystem. It was developed by Parametric TechnologiesCorporation (PTC) in the late 1980s.

SolidWorks is mechanical design automation software

I-DEAS (Integrated Design Engineering Analysis Software)is a CAD, CAM, and CAE package.CATIA (Computer Aided Three-dimensional Interactive

Application) was created by Dassault Systems of Franceand is marketed worldwide by IBM.
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I-DEAS vs. AutoCAD

2D Modeler (AutoCAD)

mostly 2D

limited 3D modeling

limited surface modeling

PC-based

3D Modeler (I-DEAS/Pro-E/UG/CATIA)

full 3D solid modeling

powerful surface modeling

feature-based, parametric solid

modeler

Workstation-based

Graphics Standards

CAD/CAM is an application program:invoke graphics functions: Devicedependency.

Program, data, programmer portability.

(Portability): Needs standards: Virtual Device: Java VM

GKS, GKS-3D, Phigs, CGM, CGI (VDI),IGES, STEP, VRML, X3D


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Standards for CAD DataExchange

Model data exchange

Share geometric data between locations.

Share geometric data between differentproprietary modelers and CAD systems.

Transfer geometric data to othersoftware applications.

analysis, CNC, etc.


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Model data exchange

Current trendMore design authority delegated tosuppliers.Suppliers must match their designs to anumber of specified variants.To support process, great deal of designdata must be exchanged.This requires CAD systems of

manufacturers and suppliers to be able toexchange geometric (and other) data.

Model data exchange

how to implement3 possible solutions to such an exchangeproblem :

1) All use the same CAD package.

2) Use special translator applications tochange data from one format to specific oneneeded.3) Use a neutral format for data exchange.


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Model data exchange

Data exchange requires standardization:

A neutral format must be standardized

Some standards have formal acceptance:National and International standards

Some are de facto standards, developed

by particular companies which chose tomake public the specifications.

Typical Situation

Major company

uses CATIA

Major supplier

uses I-DEAS

Small supplier

uses AutoCAD

Small supplier

uses Solid Edge

Partner uses

Unigraphics


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The Problem

Every CAD system uses its ownproprietary data format

Design data must be converted fromone format to the other

The solutionSo need arises for communication of

Software and Hardware via StandardCodes of Graphics Data

The Solution.!

Turnkey System Software and Hardware obtained from

one supplier(May prove satisfactory)

Suppliers of Turnkey system rarelymanufacture all items of system

Alternatively User choose specialist software and

hardware for best combination whichsuits to his application


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Types of Standards for CAD

Graphics Standards

Data Exchange Standards

Communication Standards

Aim of Graphics Standardisation

To provide versatility in thecombination of Software andHardware items of turnkey systems

To allow the creation of portable

application software package,applicable for wide range ofhardware makes and configurations


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Aim of Graphics Standardisation

To allow the transfer of graphic databetween two or more differentcompanies which may have completelydifferent CAD systems

Data Exchange Standards

To address the problem, manystandards for CAD data exchange havebeen developed

CAD systems can import and export tomany of these 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

Definition of Terms IGES (Initial Graphics Exchange Specification) VDI (Virtual Device Interface) or CGI (Computer Graphics

Interface) GKS (Graphics Kernel System) Siggraph (Graphics Standards Planning Committee of

Special Interest Group on Graphics) ACM (Association for Computing Machinery)

CORE (an American software equivalent to GKS) PHIGS (Programmers Hierarchical Interface for Graphics)

has been proposed to eliminate restrictions of GKS SET (Standard dEchange et de Transfert) ---French VDA/FS (German standard) -- DIN ANFOR (French National Standard Body)


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Levels of Graphics StandardsCommunication

CAD Database

IGES

External CADCAM System

Application SW

GKS, CORE, PHIGS

Device Drivers

Graphics Utility

VDI

Graphics Output Devices (Screens,

Plotters etc)


Level-1 (Comm. b/w Graphics UtilitySW & Graphics Output Device(screens, plotters etc) VDI (Virtual Device Interface) or CGI

(Computer Graphics Interface) is the mostimportant standard in this category

VDI specifies a standard format fortransferring GD between Graphics utility& device drivers


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Level-2 (Comm. b/w Application SW &Graphics Utility GKS (Graphics Kernel System) most

universally accepted standard developed inW. Germany in 1979.GKS provides interface between applicationpackage and Graphics utility programs forany CAD system

CORE (an American software equivalent toGKS)

PHIGS (Programmers HierarchicalInterface for Graphics) has been proposedto eliminate restrictions of GKS


Level-3 (Communication between diff.CAD SystemsIGES (Initial Graphics ExchangeSpecification) Developed b/w 1979~1982

Partially adopted by ANSIStandard format of codes for CADCAMdataCompletely independent of any systemsupplier


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Enables graphical and manufacturing datato be transferred between dissimilarsystems

Classifies different types of data interms of entities Geometry (Points, lines, arcs, planes, nodes

etc) Annotation (dimension types, center lines,

arrow leaders etc) Structures ( geometric groups, macro

definitions, circular arrays etc)

Direct Translation between CADSystems

Need a translatorfrom every CADpackage 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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Current Situation

Translation using IGES is unreliable geometry is corrupted much cleanup required after translation

Translation using STEP is notwidespread STEP translators only recently available

Existing translators lose information

parametrics and constraints features and history trees

Short-term Solutions

To avoid data translation problems,many companies have standardized on asingle 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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A Better Solution

A better solution is development ofreliable data exchange standards, usinga neutral interface

CAD 1 CAD 2 CAE 1 CAE 2

Neutral Interface

CAPP PP&C CAM CAQ

Requirements of an Interface

The interface must be capable of handlingall manufacturing data

There should be no information loss(maintain the semantics during conversion)

The system must be efficient to be

capable of handling the realtimerequirements of manufacturing

The system should be open-ended topermit extensions or contractions


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Requirements Continued

The system should be adaptable to otherstandards

The system must be independent of thecomputer and architecture used

It must be possible to form application-oriented subsets of the standard toreduce costs

The interface must be upward anddownward compatible in a hierarchicalcontrol structure.

Test procedures must be provided toverify effectively.

Initial Graphics ExchangeSpecification (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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Model data exchange

Principle neutral format at present time is IGESInternational Graphics Exchange Specification.

Established in 1979 and accepted by ANSI in 1981.

Format consists of a listing of entities and data.

Stored in ASCII coded text.

This binary format simplifies electronic

transmission.

Format used primarily for geometric data transfer

Does also support some non-geometricentities such as notes and dimensions.

Problems with IGES

Many incompatible flavors

Unreliable translation, particularly forcomplex geometry

No formal information modeling basis

Insufficient support for conformancetesting


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Model data exchangeIGES Entity Examples

Entity # Entity Description

100 Circular arc

108 Plane

110 line

114 Spline surface

118 Ruled surface

126 NURBS curve

150 CSG block162 Solid of revolution

206 Diameter dimension

Model data exchangeIGES and SolidsVendors have been slow to include solids in

translators. Some vendors (often CAMsoftware) perceived solid usage as low,with little demand.

Some felt IGES definitions too limited to

support their solid data structures.Plenty of old IGES versions still in use.Prior to 1988 no solid entities supported.1988 CSG entities added to standard.1991 B-rep entities added.


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Communication Via IGES

IGES

Pre-processor 1

Post-processor-1

Database 1

CADCAM

System 1

CADCAM

System 2

Database 2

Post-processor 2

Pre-processor 2

IGES formatAn IGES file is composed of 80-character ASCIIrecords, a record length derived from the punch cardera. Text strings are represented in "Hollerith" format.


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STEPStandart for 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

STEP Architecture

Layer 1: Implementation methods

(EXPRESS)

Physical files

Layer 2: Resource information models

Layer 3: Application protocols

Con

formancetesting

&

testsuites


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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

Status of STEP

STEP has been under development formany years, and will continue for manymore

Over a dozen STEP parts have beenapproved as international standards

Many others are under development


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STEP

STEP


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Other Standards

Standards for technical documents

Standards for images

Internet and Web standards

Continuous Acquisition and Life-cycleSupport (CALS)

Developed by US Department ofDefense

Prescribes formats for storage and

exchange of technical data Technical publications an important

focus


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Important CALS Standards

Standard Generalized MarkupLanguage (SGML)

developed in 1960s IBM

document descriptionlanguage

separates content fromstructure (formatting)

uses tags to defineheadings, sections,chapters, etc.

HTML is based on SGML

Important CALS Standards

Computer Graphics Metafile (CGM) Developed in 1986.

vector file format for illustrations anddrawings

All graphical elements can be specified in a textual

source file that can be compiled into a binary fileor one of two text representations.

IGES also used for illustrations


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Common Formats for Bitmap Images

Joint Photographic Expert Group (JPEG)

Standards

Proprietary Graphics Interchange Format (GIF)

Windows bitmap format (BMP)

Zsoft file format (PCX)

Tagged Image File Format (TIFF/TIF)

Targa file format (TGA)

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) in 1982.

Other CAD File Formats

STL 3D file format used as input for Stereo

lithography

SAT solid model file format used by ACIS-based

CAD systems


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CAD/CAM sw architecture

OpenGL, DirectX

Data Structure

Data Structure : A set of data items that are

related to each other by a set of relations: Tree,

Linked list

Vertex based, edge based, face based dataStructure


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Differentdata structures

Database

Advantages:

1) eliminate duplication,

2) standard,

3) security,

4) consistency,

5) harmonize conflicts

Types of DB: 1) relational, 2) hierarchical, 3)network, 4) OODB


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relational tables

Hierarchical DB


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Network DB

Database Management System (DBMS)

DBMS: A layer of software between the

physical DB and the users. Properties of CAD/CAM DB;

Large data items and heterogeneous types Relationship among data items are complex Frequent design changes


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Typical DBMS

Modes of Graphics Operations

Generation ofShape model

Generation ofdrawing (drafting)

3 tasks of drafting : model clean-up documentationplotting


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Relationship with database

model clean-up

It is boring and time consuming activity Overlapping entitiesNon-recoverable work : Model DB does not have

the information Time ration between model generation and

model clean-up : 1:2 ~ 1:3


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User Interface

Structure of CAD/CAM command

User Interface

CAD systems may be considered ascomprising a large number of functionsfor creating or manipulating the designmodel.Traditionally, there are two ways in which

this is achieved:Command-based systemsMenu-driven systemsIcon-driven systems


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As computers become cheaper, and morepowerful, the only interfaces of realimportance are

Graphical User Interfaces(GUI).

An example of novel technology is thevisual scanner available for 3D input.

Graphical User Interfaces(GUI)

The current demands on userinterfaces are,

on-line help adaptive dialog/response feedback ability to interrupt processes consistent modules a logical display layout deal with many processes

simultaneously


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Graphical User Interfaces(GUI)

The common trend is to adopt a userinterface which often have,

Icons A pointer device (such as a mouse) Full color Support for multiple windows, which

run programs simultaneously Popup menus

Windows can be moved, scaled,moved forward/back, etc.

Computer-aided draughting & design

Command-based systems

Command-based systems operate byreading a command and itsparameters entered by the user,carrying out the required actions,then waiting for the next command.

command (optional parameters ,target object)


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Menu-driven systems

The menu-driven approach contrastsmarkedly with the commandapproach.

The basic principle is that the user isat any time presented with a list ormenu of the functions that areavailable to be selected.

Menu tree


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The most important of these rules are:A clear, well presented screen layout.Easy function selection by a well-

structured menu system.Meaningful function names.Meaningful and helpful prompts to the

user.

Easily accessible and clearly writenhelp information


Clear screen layoutIt ensures that the user can see immediately theeffects of the use of the software functions.Graphic-basedCAE package hasa large number offunctions.

Menu area

(havingsubmenus withfunctions)


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Menu SystemThe way of displaying the sequence of menu andsubmenu selection is by the use of cascading menu(child menu).The other way of selecting software function is bymeans of

icons.


Due to the learningdifficulties ofsoftware, instead ofwritten menus thefunctions aredescribed by meansof icons.

Icon menu system aregenerally popular withCADD users.


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Prompts for userMost system have an are on the screendedicated to providing the user with promptsand instruction relating to the function beingcarried out.Some packages give various levels ofprompting and some only display aninstruction when reguested.

Operating System (OS) Module

the software that manages the sharing of theresources of a computer.

An operating system processes system data anduser input, and responds by allocating and

managing tasks and internal system resources asa service to users and programs of the system.


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Operating System

It provides the user of a computer withbasic facilities to control and managethe computer system environment.

The first computers did not haveoperating systems.

Basic interface between a user and acomputer.

It enable to run application program and

manage to store the files on disks.DOS / WINDOWS / UNIX

Operating System

CP/Mnotable early disk-based operating systemsupported on many early microcomputerslargely cloned in creating MS-DOS,

MS-DOS

wildly popular as the operating systemchosen for the IBM PC

IBM-DOS or PC-DOSIBM's version of it


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Operating System

Mac OSThe major alternative throughout the1980s in the microcomputer markettied intimately to the Apple Macintoshcomputer.

Operating System

It is the mostcommon operatingsystem in PC.

BIOS is not part ofMSDOS. It is builtinto the PC on ROM.

MSDOS

Microsoft System Disk Operating System
http://upload.wikimedia.org/wikipedia/en/f/fe/TigerDesk.png


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Operating System

By the 1990s, themicrocomputer had evolved tothe point where, as well asextensive GUI facilities, therobustness and flexibility ofoperating systems of largercomputers became increasinglydesirable.Windows NT, served as thebasis for Microsoft's entireoperating system line starting

in 1999.Windows Vista

UNIX

UNIX and VMS are two common operatingsystems for mainframes and workstations.

It was developed as a simple operatingsystem for use a minicomputers.

It was written in the C prog. language.

It has been implemented on a wide range ofcomputers from PCs to mainframes.

(MicroVAX, SUN, HP Apollo, SiliconGraphics, IBM RS6000)
http://upload.wikimedia.org/wikipedia/en/3/38/Windows_xp_desktop.PNG


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UNIX

Hobbyist-developedreimplementations of Unix,assembled with the toolsfrom the GNU Project,also became popular;versions based on theLinux kernel are by far themost popular, with theBSD derived UNIXes

holding a small portion ofthe server market.

What is Programming Language ?

an artificial language that can be used tocontrol the behavior of a machine,particularly a computer.

Programming languages, like humanlanguages, are defined through the useof syntactic and semantic rules, todetermine structure and meaningrespectively.
http://upload.wikimedia.org/wikipedia/en/8/83/Linux_sreenshot.jpg


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Programming Languages

1st generationThe processor only operates using

programming language (machine code).Very few programmers can create

programs directly using machine code.2nd generationAssembly language defines each machine

code instruction as a mnemonic called anassembler.

Programming Languages

3rd generation programming languages(3GLs); instruct the computer step bystep how to solve a problem.

4th & 5th generation programming

languages ; state the solution and a setof rules for achieving it.Prolog, OPS5, and Mercury are the bestknown fifth-generation languages.


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Assembly language

class of low-level languages used to write computerprograms,

or to a particular such language. human-readable notation for the machine language

used to control a specific computer architecture. was once widely used for all aspects of programming.

Today it is used in limited situations, primarily whendirect hardware manipulation or unusual performance

issues are involved.

High Level Language

It enables to define a program or solve aproblem using a code.

Compiler : converts the program into aintermediate object code.

Linker : linkes between the library andprogrammers code (file)

Execution : runs code and gets results


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High Level Language

Source Code

=Program file=

COMPILER LINKER

Intermediate

Object

code

Library(procedure/

Function /

Subroutine)

FILE

Independent

code

Computer-dependent

operations

FORTRAN (FORmula TRANslation)

It enables the programmer to write mathematicalformulae in algebraic form for soultion.

FORTRAN is a general-purpose, procedural, imperativeprogramming language that is especially suited tonumeric computation and scientific computing. Originallydeveloped by IBM in the 1950s for scientific andengineering applications,

The first manual for FORTRAN appeared in 1956, withthe first FORTRAN compiler delivered in 1957.


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COBOL

is a third-generation programming language,and one of the oldest programminglanguages still in active use.

Its name is an acronym, for COmmonBusiness Oriented Language, defining itsprimary domain in business, finance, andadministrative systems for companies andgovernments.

COBOL-68 COBOL-74 COBOL-85

COBOL 2002

BASIC (Beginners All-purpose SymbolicInstruction Code)

is never compiled and linked. Quick andsimple program. (1964)

PASCAL was developed in the late 1960s,first structured language,.

C language combines high level languagesyntax with lower level assemblyprogramming.


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Modeling and Viewing

Modeling is the art of abstracting or

representing a phenomenon. 2.5 dimension: same thickness Deleting a view does not delete the graphic

entity from DB Graphic entity should be explicitly deleted by

the user from the DB

2.5dimension and 3D shape model


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telephone model

Hierarchy of the geometric model DB


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Standard viewing directions

Computer-aided draughting &design

Two-dimensional (2D)computer drawing is therepresentation of anobject in the single-viewformat which shows twoof the three object

dimensions or the

mutiview format where each view

reveals two

dimensions.


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Standard 2D views


Three-dimensional (3D) computerdrawing is the coordinate format. Threedimensional computer aided drawingallows the

production of geometric

models of a component or

product for spatial and

visual analysis.


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Standard 3D views


2D Vs 3D DOCUMENTATION

The product documentation has traditionally beenrecorded on 2D paper drawings. The trend is towardboth an electronic paperless environment and using a3D representation rather than 2D drawings.

Companies tend toward either a model-centric or adrawing-centric philosophy of how their productsare documented.

A drawing-centric company may perceive of 3D partmodels as a preliminary step to create 2D drawings,but the released 2D drawings are archived todocument the final design.


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2D vs 3D DOCUMENTATION

A model-centric company may hold aview that the 3D part model containsthe master information, and the 2Ddrawings are only an intermediate formof communication to transmitinformation to suppliers who needprinted drawings.

Fundamentals of CAD

Documents