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Chapter 3 CAD/CAM Software

Soonhung Han

[email protected]

http://me.kaist.ac.kr/newcourse/index.php?code=MAE474

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3.1 Introduction

3.2 Graphics Standards 3.3 Basic Definitions

3.4 Modes of Graphics Operations

3.5 User Interface 3.6 Software Modules

3.7 Modeling and Viewing

3.8 Software Documentation

3.9 Software Development

3.10 Efficient Use of CAD/CAM Software

3.11 Software Trends

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3.1 Introduction

NSF Center for Productivity: CAD/CAM has morepotential to radically increase productivity than anydevelopment since electricity.

CAD/CAM speeds up the design process: productivity,innovation, creativity.

Release engineers from time consuming tasks with lowlevel intelligence

Semantics: principles and theories (원리와 이론)underlying the given field.

Syntax: format of inputs and outputs. (형식)

One integrated database: change propagation is

automatic

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Fig. 3-1 CAD/CAM learning curve

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3.2 Graphics Standards

CAD/CAM is an application program:invoke graphics functions: Device

dependency.Program, data, programmer portability. (이식성): Needs standards:

Virtual Device: Java VM GKS, GKS-3D, Phigs, CGM, CGI (VDI),IGES, STEP, VRML, X3D

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Fig. 3-2 CAD/CAM sw architecture

OpenGL, DirectX

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3.3 Basic Definitions

3.3.1 Data Structure

3.3.2 Database 3.3.3 Database Management System (DBMS)

3.3.4 Database Coordinate System

3.3.5 Working Coordinate System 3.3.6 Screen Coordinate System

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3.3.1 Data Structure

Data Structure (자료구조): A set of data

items that are related to each other by a set

of relations: Tree, Linked list

Vertex based(꼭지점 위주), edge based(변

위주), face based (

사각형위주) dataStructure

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Fig. 3-3

Different

data structures

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3.3.2 Database

Advantages: 1) eliminate duplication, 2)

standard, 3) security, 4) consistency, 5)

harmonize conflicts

Types of DB: 1) relational(관계형 ), 2)

hierarchical(계층형

), 3) network(네트워크

형), 4) OODB(객체지향형)

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Fig. 3-4 relational tables for Fig. 3-3

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http://slidepdf.com/reader/full/ch03sw 12/42Fig. 3-5 Hierarchical DB

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Fig. 3-6 Network DB

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Requirements for CAD/CAM DB

Heterogeneous applications

Dynamic modification

Tentative, iterative, evolutionary nature of the design process

Versions, levels of detail (LOD)

Concurrent and multiple users

Temporary DB Different designs require different design sequences

Easy access: should not require extensive knowledgeon DB to extract the data.

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3.3.3 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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http://slidepdf.com/reader/full/ch03sw 16/42Fig. 3-8 Typical DBMS

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3.3.4 Database Coordinate System

Working coord., Model coord. (= DB coord.,

World cood.), Screen coord.

Modeling coord., World coord., Device

coord. of PHIGS

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MCSWCS

VCS

NPCDCS

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3.3.5 Working Coordinate System

Local coord., Global coord.

Coordinate transformation: See Ch. 9

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3.3.6 Screen Coordinate System

Fig. 3-16 Screen layout

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3.4 Modes of Graphics Operations

Generation of Shape model

Generation of drawing (drafting)

3 tasks of drafting :

model clean-up(모델 다듬기)

documentation(문서화 )

plotting(도형화 )

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Fig. 3-17 Relationship with database

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model clean-up (모델 다듬기)

It is boring and time consuming activity

Overlapping entities

Non-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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3.5 User Interface

Fig. 3-18 Structure of CAD/CAM command

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Fig. 3-19 Menu tree

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3.6 Software Modules

3.6.1 Operating System (OS) Module

3.6.2 Graphics Module 3.6.3 Applications Module

3.6.4 Programming Module (컴파일러)

3.6.5 Communication Module (인터넷)

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3.6.1 Operating System (OS) Module

Text file and graphics file UNIX, Windows

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3.6.3 Applications Module

Geometric model is a mean, not a goal of

engineers.

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3.6.4 Programming Module

Macro Programming: VarPro2, CVMac,

DAL, GRIP Visual Basic

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3.6.5 Communication Module

CIM: computer integrated manufacturing

(컴퓨터 통합생산)

IGES (initial graphics exchange

specifications), STEP (standard for the

exchange of product model data)

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3.7 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 deletedby the user from the DB

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Fig. 3-43 2.5dimension and 3D shape model

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Fig. 3-44 telephone model

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Fig. 3-45 Hierarchy of the geometric model DB

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Fig. 3-46 Standard viewing directions

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Fig. 3-47 Standard 2D views

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Fig. 3-48 Standard 3D views

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3.8 Software Documentation

Reference manual

User manual On-line manual

Developers manual

System manual

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3.9 Software Development

Customization

Two SW developments;

Need to know about the DB structure

DO not need the knowledge

3 10 Efficient Use of CAD/CAM

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3.10 Efficient Use of CAD/CAM

Software

Fig. 3-49 Modeling a 2.5D object

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3.11 Software Trends

Software changes more slowly thanhardware: bounded by basic principles.

Software bottleneck

Integration and automation of thedevelopment process

Solid modeling seems to be the keytechnique to automate and integrateCAD/CAM.

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Fig. 3-51

Sales of CAD/CAM system

components

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