COMPUTER AIDED DESIGN FOR 5th SEMESTER MECHANICAL ENGINEERING OF ANNA UNIVERSITY (Chennai, Trichy, Coimbatore & Tirunelveli)
Dr. G.K. VIJAYARAGHAVAN, B.E., M.Tech., Ph.D. Adviser, Dhaanish Ahmed College of Engineering, Padappai, Chennai, Tamilnadu. E-mail:
[email protected] Website: wwww. gkvbooks.comm
Dr. S.SUNDARAVALLI, M.Tech., Ph.D. Associate Professor, Department of Mechanical Engineering, B.S. Abdur Rahman University, Vandalur, Chennai.
LAKSHMI PUBLICATIONS Plot No.73, Gokul Nagar, 2nd Main Road (40 Feet Road), Perumbakkam, Medavakkam (P.O), Chennai – 600 100, Tamil Nadu, INDIA. Phone: 044 - 49523977, 98945 98598, 96772 21371. E-mail:
[email protected],
[email protected]
COMPUTER AIDED DESIGN By Dr. G.K. Vijayaraghavan & Dr. S. Sundaravalli First Edition: July 2015
© All rights are exclusively reserved by the author(s) No part of this publication can be reproduced, stored in a retrieval system or transmitted in any form or by any means, mechanical, photocopying, recording or otherwise, without the prior written permission of the author.
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PREFACE We are pleased to bring out our fully revised sixth edition “COMPUTER AIDED DESIGN” book for Engineering and Technology studies. This book is based on the latest syllabi prescribed by the Anna University Chennai, Trichy, Coimbatore & Tirunelveli for 5th Semester Mechanical engineering students of its affiliated colleges. Almost all the engineering industries are benefited in several ways by the integration of computers into the product design, development and manufacturing. CAD technology makes use of the computer to create drawings of parts and assemblies on computer files which can be further utilized for analysis and manufacturing purposes. The various features of the product can be evaluated during design stage itself by using computers. This has been made possible through the use of design workstations or CAD terminals, and graphics and analysis softwares which help the designer to optimize the design. Thus, for a design engineer, it is essentially required to have the knowledge of CAD. Unit 1 deals with the fundamentals of computer graphics in which in which product cycle, design process, sequential and concurrent engineering, CAD system architecture, computer graphics, co-ordinate systems, 2D and 3D transformations, homogeneous coordinates, line drawing, clipping, and viewing transformation are discussed. Elaborate treatment of analytical and theoretical nature is provided in all topics. Unit 2 has an in depth dealing of geometric modeling. The topics covered in this unit are representation of curves, Hermite curve, Bezier curve, B-spline curves, rational curves, techniques for surface modeling, surface patch, Coons and bicubic patches, Bezier and Bspline surfaces. It also covers solid modeling techniques such as CSG and B-rep. Visual realism techniques such as hidden line, surface and solid removal algorithms, shading, colouring, and computer animation techniques have been discussed in Unit 3. Unit 4 deals with the assembly modeling, inference of positions and orientation, tolerance analysis, mass property calculations, mechanism simulation and interference checking.
Standards for computer graphics, Graphical Kernel System (GKS), standards for exchange images, Open Graphics Library (OpenGL), data exchange standards such as IGES, STEP, CALS etc. and communication standards are treated elaborately in Unit 5. Important solved problems and questions have been added in each unit which will enable the students to score high marks in the University examinations. In addition to this, two mark questions and answers are added at the tail end of each unit. With these features, we sincerely hope that this book would serve as a valuable text for the students. Though efforts have been taken aiming at a ‘zero flaw’ content, we do recognize that mistakes may have inadvertently crept in. We welcome constructive criticisms on any specific topics of this book. Our sincere thanks to Mrs. Nirmala Durai, Proprietor of “Lakshmi Publications” and Publishing Advisor Mr. A. DURAI, B.E. for their involvement to make this publication successful. - Authors
ME6501 UNIT I
COMPUTER AIDED DESIGN
FUNDAMENTALS OF COMPUTER GRAPHICS
Product cycle - Design process - sequential and concurrent engineering - Computer aided design – CAD system architecture - Computer graphics – co-ordinate systems 2D and 3D transformations - homogeneous coordinates - Line drawing - Clipping viewing transformation. UNIT II GEOMETRIC MODELING Representation of curves - Hermite curve - Bezier curve - B-spline curves - rational curves -Techniques for surface modeling – surface patch - Coons and bicubic patches - Bezier and B-spline surfaces. Solid modeling techniques - CSG and B-rep.
UNIT III VISUAL REALISM Hidden – Line - Surface - Solid removal algorithms – shading – colouring – computer animation. UNIT IV ASSEMBLY OF PARTS Assembly modelling – interferences of positions and orientation – tolerance analysis mass property calculations – mechanism simulation and interference checking.
UNIT V CAD STANDARDS Standards for computer graphics - Graphical Kernel System (GKS) - standards for exchange images - Open Graphics Library (OpenGL) - Data exchange standards IGES, STEP, CALS etc. - communication standards.
CONTENTS
CONTENTS
UNIT 1 Fundamentals of Computer Graphics UNIT 2 Geometric Modeling UNIT 3 Visual Realism UNIT 4 Assembly of Parts UNIT 5 CAD Standards
C-10
Contents
UNIT 1 FUNDAMENTALS OF COMPUTER GRAPHICS 1.1.
Introduction to CAD/CAM
1.1
1.2.
Product cycle
1.2
1.3.
Design process
1.4
1.3.1. Shighely model
1.5
1.3.2. Pahl and Beitz model
1.6
1.3.3. Ohsuga model
1.8
1.3.4. Earle model
1.8
1.4.
Morphology of design
1.12
1.5.
Sequential engineering
1.17
1.5.1. Advantages and disadvantages of sequential engineering
1.18
Concurrent engineering
1.18
1.6.1. Characteristics of concurrent engineering
1.20
1.6.2. Advantages of concurrent engineering
1.20
1.6.3. Features for the success of concurrent engineering
1.20
1.6.4. Comparison between concurrent engineering and sequential engineering
1.21
Computer aided design
1.22
1.7.1. Roles of CAD in design
1.23
1.7.2. Development and use of CAD
1.23
1.7.3. CAD process
1.24
1.7.4. Applications of CAD
1.27
1.7.5. Advantages of CAD
1.28
1.8.
CAD system architecture
1.28
1.9.
Computer graphics
1.30
1.9.1. Advantages of computer graphics
1.32
1.9.2. Applications of computer graphics
1.32
Coordinate systems in computer graphics
1.33
1.6.
1.7.
1.10.
C-20
Computer Aided Design
1.10.1. Left and right handed coordinate systems
1.33
1.10.2. Multiple coordinate systems
1.34
Transformations
1.35
1.11.1. Display transformation in 2Dor 2D display control facilities
1.35
1.11.2. Display transformation in 3D or 3D display control facilities
1.41
Two dimensional 2D transformation
1.42
1.12.1. Translation
1.43
1.12.2. Scaling
1.44
1.12.3. Reflection
1.45
1.12.4. Rotation
1.45
1.12.5. Shearing
1.46
1.13.
Concatenation or combined transformation
1.47
1.14.
Homogeneous coordinates
1.49
1.15.
Homogeneous transformation
1.51
1.16.
Solved problems on 2D transformations
1.52
1.17.
Three dimensional (3D) transformations
1.118
1.17.1. Solved problems on 3D transformation
1.120
Line drawing
1.126
1.18.1. Digital differential analyzer (DDA) algorithm
1.126
1.18.2. Solved problems on DDA algorithm
1.127
1.18.3. Bresenham's line algorithm
1.130
1.18.4. Solved problems on Bresenham’s algorithm
1.132
Clipping
1.138
1.19.1. Point clipping
1.140
1.19.2. Line clipping
1.140
1.19.3. Polygon clipping
1.142
1.19.4. Solved problem on clipping
1.145
1.20.
Viewing transformation
1.147
1.21.
Normalized transformation
1.148
1.22.
Workstation transformation
1.149
1.11.
1.12.
1.18.
1.19.
C-30
Contents
1.22.1. Solved problem on workstation transformation
1.151
1.23.
Two mark questions and answers
1.152
1.24.
Solved questions
1.164
UNIT 2 GEOMETRIC MODELING 2.1.
Representation of curves
2.1
2.1.1. Mathematical representation of curves
2.1
2.1.2. Free form or synthetic curves
2.3
2.1.3. Order of continuity
2.3
2.1.4. Interpolation and approximation modeling
2.5
Hermite curve
2.5
2.2.1. Solved problems on Hermite curve
2.9
Bezier curve
2.15
2.3.1. Mathematical formulation of Bezier curves
2.15
2.3.2. Cubic Bezier curves
2.18
2.3.3. Characteristics of the Bezier curves
2.19
2.3.4. Difference between cubic spline and Bezier curves
2.19
2.3.5. Solved problems on Bezier curves
2.20
B-spline curve
2.29
2.4.1. Characteristics of the B-spline curves
2.31
2.4.2. Uniform and non-uniform B-spline curves
2.33
2.4.3. Open and closed B-spline curves
2.34
2.4.4. Cubic B-spline curves
2.36
2.5.
Rational curves
2.37
2.6.
Surface modeling
2.39
2.6.1. Types of surfaces
2.40
2.6.2. Applications of surface modeling
2.46
2.6.3. Advantages and disadvantages of surface modeling
2.46
2.2.
2.3.
2.4.
C-40
Computer Aided Design
2.7.
Techniques for surface modeling
2.47
2.8.
Surface patch
2.48
2.8.1. Analytical and synthetic surfaces
2.50
Coons surface
2.50
2.9.1. Bilinear coons surface
2.51
2.9.2. Applications of coons surface
2.52
2.10.
Bicubic surface patch
2.53
2.11.
Hermite Bicubic surface
2.54
2.11.1. Solved problems on Bicubic surface patch
2.57
Bezier surface
2.59
2.12.1. Cubic Bezier surface
2.60
2.12.2. Properties of Bezier surface
2.63
2.12.3. Advantages and disadvantages of Bezier surface
2.64
B-spline surface
2.64
2.13.1. Cubic B-spline surface
2.65
Solid modeling
2.66
2.14.1. Solid model representation
2.67
2.14.2. Solid modeling entities
2.67
2.14.3. Solid modeling approaches
2.68
2.14.4. Representation of a solid
2.70
2.14.5. Representation schemes
2.71
2.14.6. Advantages of solid modeling
2.73
2.15.
Constructive solid geometry (CSG)
2.73
2.16.
Boundary representation (B-rep)
2.77
2.17.
Two mark questions and answers
2.85
2.18.
Solved questions
2.97
2.9.
2.12.
2.13.
2.14.
C-50
Contents
UNIT 3 VISUAL REALISM 3.1.
Visual realism
3.1
3.2.
Hidden line removal
3.4
3.2.1. Hidden line elimination process
3.5
3.2.2. Visibility techniques
3.6
Hidden line removal algorithms
3.10
3.3.1. Depth or priority algorithm
3.11
3.3.2. Area-oriented algorithm
3.15
3.3.3. Overlay algorithm
3.17
3.3.4. Robert’s algorithm
3.17
Hidden surface removal algorithms
3.18
3.4.1. Depth-buffer algorithm or z-buffer algorithm
3.19
3.4.2. Area-coherence algorithm or Warnock’s algorithm
3.21
3.4.3. Scan-line algorithm or Watkin’s algorithm
3.23
Hidden solid removal algorithms
3.26
3.5.1. Ray-tracing or ray-casting algorithm
3.26
Shading
3.28
3.6.1. Illumination models or shading models
3.30
3.6.2. Shading algorithms
3.32
3.6.3. Shading enhancements
3.40
Colouring
3.44
3.7.1. Colour models
3.46
3.7.2. Interpolation of colours
3.51
3.7.3. Gamma correction
3.51
Computer animation
3.52
3.8.1. Applications of animation
3.53
3.8.2. Conventional animation
3.54
3.8.3. Computer animation
3.57
3.3.
3.4.
3.5.
3.6.
3.7.
3.8.
C-60
Computer Aided Design
3.8.4. Animation types
3.62
3.8.5. Animation techniques
3.66
3.8.6. Simulation approach
3.72
3.8.7. Hybrid approach
3.72
3.8.8. Camera animation
3.73
3.8.9. Animation software packages
3.73
3.8.10. Animation video and digital movie making tools
3.74
3.9.
Two mark questions and answers
3.75
3.10.
Solved questions
3.88
UNIT 4 ASSEMBLY OF PARTS 4.1.
4.2.
4.3.
Assembly modeling
4.1
4.1.1. Generation of assembly model
4.2
4.1.2. Modeling and representation of parts
4.4
4.1.3. Assembly modeling approaches
4.4
4.1.4. Hierarchical relationship
4.5
4.1.5. Mating conditions
4.8
4.1.6. Representation of assemblies and assembly plans
4.14
4.1.7. Generation of assembly sequences and assembly plans
4.15
Inference of position and orientation
4.16
4.2.1. Solved problems on assembly modeling
4.21
Tolerance analysis
4.29
4.3.1. Used in tolerance analysis
4.30
4.3.2. Hole basis and shaft basis system
4.33
4.3.3. Fits and types of fits
4.35
4.3.4. Numerical examples of various fits
4.37
4.3.5. ISO system of tolerances
4.39
4.3.6. Tolerance grades
4.40
C-70
Contents
4.3.7. Solved problems on tolerance analysis
4.41
4.3.8. Calculation of fundamental deviation
4.44
4.3.9. Solved problems on fundamental deviations
4.45
4.3.10. Methods of indicating tolerances on drawing
4.47
4.3.11. Geometrical tolerances
4.49
4.3.12. Tolerance accumulation
4.51
4.3.13. Tolerance/cost relationship
4.53
4.3.14. Tolerance modeling
4.54
4.3.15. Methods for Tolerance Analysis
4.54
Mass property calculations
4.61
4.4.1. Mass
4.61
4.4.2. Centroid or centre of gravity
4.62
4.4.3. First moment of inertia
4.63
4.4.4. Second moment of inertia and products of inertia
4.63
Mechanism simulation
4.64
4.5.1. Mapping mating constraints to kinematic joints
4.66
4.5.2. Denavit-Hartenberg (D-H) representation
4.70
4.5.3. Solved problems on kinematic mechanism
4.75
Interference checking
4.85
4.6.1. Determining interference relationships between parts
4.86
4.6.2. Interference-free matrix
4.87
4.7.
Two mark questions and answers
4.88
4.8.
Solved questions
4.93
4.4.
4.5.
4.6.
UNIT 5 CAD STANDARDS 5.1
Introduction to CAD standards
5.1
5.2.
Database Management
5.2
5.3.
Standards for computer graphics
5.4
5.4.
Classification of CAD standards
5.5
C-80
Computer Aided Design
5.4.1. Graphics and computing standards
5.6
5.4.2. Types of graphics standards
5.7
5.4.3. Classification of graphics standards based on functions
5.8
Graphics kernel system (GKS)
5.8
5.5.1. Features of GKS
5.9
5.5.2. Coordinates in GKS
5.9
5.5.3. Classification of GKS
5.10
5.5.4. GKS primitives
5.10
5.5.5. GKS inquiry functions
5.14
5.5.6. GKS input functions
5.15
5.5.7. Other graphic standards
5.16
5.5.7.1. GKS-3D
5.16
5.5.7.2. PHIGS - Programmers Hierarchical Interactive Graphics Standard
5.17
5.5.7.3. NAPLPS-North American Presentation Level Protocol Syntax
5.19
Standards for exchange images
5.19
5.6.1. Open graphics library (OpenGL)
5.19
Data exchange standards
5.26
5.7.1. Requirements of data exchange
5.28
5.7.2. Methods of data exchange
5.28
5.7.2.1. Direct CAD system export/import
5.29
5.7.2.2. Direct translation software
5.29
5.7.2.3. Neutral data exchange formats
5.29
5.7.3. Approaches in data exchange format
5.20
5.7.4. Classification of data exchange standards or neutral file formats
5.32
5.7.4.1. IGES – initial graphics exchange specification
5.32
5.7.4.2. Drawing exchange format (DXF)
5.39
5.8.
STEP - Standard for exchange of product model data
5.40
5.9.
Continuous acquisition and life-cycle support (CALS)
5.43
5.9.1. CALS in AutoCAD
5.50
5.5.
5.6.
5.7.
C-90
Contents
5.10.
PDES - Product Data Exchange Standard
5.51
5.11.
Other data exchange standards
5.52
5.12.
Communication standards
5.53
5.12.1. Levels of graphics standards communication
5.54
5.13.
Two mark questions and answers
5.55
5.14.
Solved questions
5.68
