CHAPTER 3
Computer-Aided Design
and Drafting (CADD)
Learning Objectives
• Define CADD and CAD
• Describe the CADD workstation and
peripheral equipment
• Identify common CADD software
manufactures and products
• Describe and compare CADD formats
• Identify disciplines and industry
concepts related to CADD
Learning Objectives
• Explain the use of animation and virtual
reality in the design process
• Demonstrate an understanding of basic
CADD techniques including drawing and
editing, line standards and layers, reusing
content, plotting, file templates, and
storing and managing files
• Explain basic surface and solid modeling
techniques
Learning Objectives
• Demonstrate an understanding of
parametric solid modeling
• Identify, describe, and use national
CADD standards
• Discuss issues related to productivity
with CADD
• Describe sustainable design and CAD
practices
Computer-Aided Design and
Drafting (CADD)
• Entire range of design and drafting
with the aid of a computer
• Computer-aided design (CAD)
• Computer-aided drafting (CAD)
• Used by several industries and most
engineering and architectural related
disciplines
CADD Workstation
• Hardware
• Computer provides:
• Data processing
• Calculations
• Communication with peripheral
equipment
CADD Software Products
• Numerous and constantly changing
• Many CADD software manufactures
• Rapidly evolving CADD market
CADD Software Products
• General-purpose
• Mechanical computer aided design
(MCAD)
• Other disciplines such as architectural,
civil, structural
• Software packages
• Product lifecycle management (PLM)
Common CADD Software
Manufactures
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Alibre, Inc.
Ashlar-Vellum
Autodesk, Inc.
Bentley Systems,
Inc.
Dassault Systèmes
Google Inc.
GRAPHISOFT
IMSI/Design, LLC
• Intergraph
• IronCAD
• Kubotek
Corporation
• Parametric
Technology
Corporation
• Siemens
Corporation
Common CADD Formats
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2-D drawings
3-D wireframe models
3-D surface models
3-D solid models
Choosing a CADD Format
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Design and drafting practices
Project requirements
Collaboration and communication
Software and training costs
Known industry standard product
Stability and usability
Support and training
Personal preference
Two-Dimensional (2-D) Drawings
• Established and often required design and
drafting format
• Common in all engineering and
architectural industries and related
disciplines
• Describes design intent and product
requirements
• Can provide computer numerical control
(CNC) machine code
2-D Drawings
Three-Dimensional (3-D)
Wireframe Models
• Basic 3-D CAD model
• Include object edges and vertices
• Can provide geometry for:
• 2-D drawings
• 3-D computer numerical control (CNC)
machine code
• Replaced by 3-D surface and solid
modeling
3-D Wireframe Models
3-D Surface Models
• Include object edges, vertices, and
surfaces
• Complex curves and forms
• Can provide geometry for:
• 2-D drawings
• 3-D solid models
• 3-D computer numerical control (CNC)
machine code
3-D Surface Models
3-D Solid Models
• Most complex CAD format
• Include object edges, vertices, surfaces,
and mass
• Exact digital representation of a product
• May require some surface modeling
• Offer engineering analysis and testing
• Can provide geometry for:
• 2-D drawings
• 3-D computer numerical control (CNC)
machine code
3-D Solid Models
Industry and CADD
• CADD can store many forms of data
• CADD supports:
• Manufacturing
• Marketing
• Sales
• Service
• Maintenance
Product Lifecycle Management
(PLM)
• Supported by CADD
• PLM software helps coordinate:
• Design and manufacturing
• Visualization and presentation
• Maintenance and disassembly
Web-Based Collaboration
• Common to modern design and drafting
• Supports the design and documentation
process
• Uses product data management (PDM)
systems
• Allows for increased outsourcing
Prototyping
• Prototype
• Helps confirm a
design
• Typically occurs in
the development
phase of the
design process
Prototyping
• Digital prototype • Conventional
(shown)
machining
• Rapid prototyping
• Rapid injection
molding
• Subtractive Rapid
Prototyping
Computer-Aided Engineering
(CAE)
• Involves:
• CAD
• Computer-aided
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industrial design
(CAID)
CAD/CAM
CNC
CIM
• PDM
• Web-based
collaboration
Animation
• Engineering animations
• Basic element of product design and
analysis
• eLearning animations
• Additional classroom learning tool or an
online or distance learning presentation
• Entertainment animations
• Movies, television, and video games
Computer-Aided Manufacturing
(CAM)
• Major innovation
• Common process
• Helps produce consistent and quality
products
• Computer-aided design/computeraided manufacturing (CAD/CAM)
• Computer numerical control (CNC)
Computer-Integrated
Manufacturing (CIM)
• Computer and software controls most,
if not all, portions of manufacturing
• Incorporates CAD, CAM, robotics,
electronics, hydraulics, pneumatics,
computer programming, and process
control
Additional CADD Applications
• Sales and marketing
materials
• Technical publications
• Training documents
• Product brochures
• Installation and service
manuals
• Technical illustration
(shown)
Virtual Reality (VR)
• Allows one or more people to move
and react in a computer-simulated
environment
• Provides interaction with a model
during the design process
• Requires special interface devices
• Walk-through
• Fly-through
VR Applications and Devices
• Through-the-window VR (passive VR)
• Head Mounted Display (HMD)
• Binocular Omni-Orientation Monitor
(BOOM)
• Cave Automatic Virtual Environment
(CAVE)
• Haptic Interface
• Web-Enabled Virtual Reality Modeling
Language (VRML)
Basic CADD Techniques
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Drawing and Editing
Line Standards and Layers
Reusing Content
Plotting
File Templates
Storing and Managing Files
Drawing and Editing
• Commands for creating and modifying
all elements of a drawing
• Techniques vary depending on:
• CADD software
• Preferred design techniques
Drawing and Editing
Line Standards and Layers
• Help organize and assign properties to
objects
• Separate objects into logical groups for
formatting and display purposes
Line Standards and Layers
Example Mechanical Drafting
Layers
Layer Name
Line Type
Line Weight
Color
Object
Solid (Continuous)
.02 in. (0.6 mm)
Black
Hidden
Hidden (Dashed)
.01 in. (0.3 mm)
Blue
Center
Center
.01 in. (0.3 mm)
Green
Dimension
Solid (Continuous)
.01 in. (0.3 mm)
Red
Construction
Solid (Continuous)
.01 in. (0.3 mm)
Yellow
Border
Solid (Continuous)
.02 in. (0.6 mm)
Black
Phantom
Phantom
.01 in. (0.3 mm)
Magenta
Section
Solid (Continuous)
.01 in. (0.3 mm)
Brown
Reusing Content
• CADD offers the ability to reuse:
• Objects and object properties
• Text and dimension settings
• Drafting symbols
• Sheets
• Typical drawing details
Plotting a Hard Copy
• Often required
• Creates a plot that can be viewed and
marked without having a computer
• Each CADD system uses a specific
method to plot
• Plotting theory is similar
• Electronic plotting (exporting)
Drawing Scale and Scale Factor
• Important consideration when plotting
• Automated by most CADD software,
• Remains an important concept
• Example application:
• A 1:4 scale drawing has a scale factor of 4
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(4  1 = 4)
Multiply the scale factor of 4 by values
such as text height of .12 in. (3 mm) to
find the .48 in. (12 mm) scaled text height
File Templates
• Preset settings for specific applications
• Standard items required for multiple
projects
• Save time
• Improve consistency
Common Elements of a File
Template
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Units settings
Drawing and design settings and aids
Layers
Color, material, and lighting standards
Annotation standards
Common symbols
Display settings
Sheets and sheet items
Plot settings
Storing and Managing Files
• Save files immediately after you begin
work
• Save at least every 10 to 15 minutes
• Develop an organized structure of file
folders
• Use a specific file naming system
• Follow established file management
techniques
Surface Modeling Techniques
• Polygonal modeling
• Surfaces are quick and easy to modify
• Common for character design for games
• NURBS
• Non-uniform rational basis spline
• Non-uniform rational B-spline
 Accurate
curves and surfaces
 Used by most CAD systems
NURB Geometry
• Complex mathematical spline
representation with control points
• Change control points to alter the
curve
NURB Geometry
Direct Surface Modeling
Procedural Surface Modeling
Solid Primitives
• Boolean operations
• Also apply to more complex solid models
Feature-Based Solid Modeling
• Construct solid models using intuitive
feature tools
• Often begins with a 2-D sketch
• Sketch used to develop a sketched feature
• Additional features add or subtract solid
material
Parametric Solid Models
• Most common feature-based solid
models
• Often store model history
• History-based solid modeling
• Captures design intent using
parameters
• Maintains design constraints
History-Free Solid Modeling
• Often associated with basic solids
(dumb solids)
• Makes design changes easy
• Helps support collaboration
• Explicit modeling
Parametric Solid Model Work
Environments
• Part
• Assembly (subassemblies and assembly)
Part Model Elements
• Sketch
• Sketched feature
• Placed (built-in, added, automated)
features
• Feature pattern
• Reference (work, reference geometry)
features
• Catalog (library) feature
Assembly Modeling
• Add and constrain existing components
• Bottom-up design
• Create components within an assembly
file (in-place)
• Top-down design
• Assembly constraints (mates)
Assembly Modeling
Extracting Drawing Content from
Models
• Editing the model adjusts the corresponding
drawing
• Some edits to the drawing modify the linked
model
CADD Standards
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Design and drafting requirements
Appearance
Technique
Operating procedures
Record keeping method
CADD Standards
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File storage, naming, and backup
File templates
Units of measurement
Layout characteristics
Borders and title blocks
Symbols
Layers, and text, table, and dimension
styles
• Plot styles and plotting
CADD Standards
• American Society of Mechanical
Engineers (ASME) standards
• CADD Skill Standards
• United States National CAD Standard
Design Planning
• Important and productive time
• Determines how you approach a
project
• Without proper planning you may
become frustrated and waste time
Design Planning
• Helps establish:
• Drawing layout
• Drafting settings
• How and when to perform specific tasks
• What objects and symbols to create
• The best use of CADD and equipment
• An even workload
Ergonomic Workstation
• Helps prevent most computer-related
injuries
Positive Work Habits
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Concentrate on good posture
Keep your stress level low
Take periodic breaks
Apply stretching and other exercises
Locate noisy plotters in a separate room
and keep other noise to a minimum
• Ensure adequate air-conditioning and
ventilation
Stretches to Help Avoid Repetitive
Injury