Section 1 Introduction to Drafting Chapter 3 Introduction to CAD

Section 1Section 1Introduction to Introduction to

DraftingDrafting

Chapter 3Chapter 3

Introduction to CADIntroduction to CAD

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.3

Objectives

• Explain computer-aided drafting and design.• Identify common applications for CAD in

different areas of drafting.• List the components of a typical CAD

workstation.• Identify features of CAD software and how they

should be evaluated when selecting a program.• Explain the advantages of specific CAD

applications.


What Is CAD?

• Tool used to plan and design parts.• Automates symbol creation and object

duplication.• Incorporates hardware and software.• Requires knowledge of drafting principles and

practices.


Why Use CAD?

• Productivity• Flexibility• Uniformity• Ease of scaling

(EdgeCAM/Pathtrace)


CAD Productivity Benefits

• Significant time and money savings over manual drafting.

• Increased drawing quality.

• Reduced number of revisions.

• Symbol library applications.

• Schedule generation and analysis tools.


Symbol Library


CAD Flexibility Benefits

• Plotting at a variety of scales.

• Presentation and media options.

• Data sharing.


CAD Uniformity Benefits

• Accurate adherence to standards.

• Consistent symbol generation.

• Ensured line quality.


CAD Scaling Benefits

• Objects typically drawn at full size.

• Drawing plotted at specified scale.

• Drafting time and potential for errors minimized.


Mechanical CAD Applications

• Automatic schedule generation.

• Rendering capability.

• Animation functions.


Part Schedule Production


CAD Workstation

• Used together with CAD software.

• Often connected to other devices in network.

• May be connected to mainframe.


CAD Workstation (Cont.)


Computer Components

• Central processing unit (CPU)

• Output device

• Input device

• Storage devices


Storage Devices

• Used to save data for later use.• Computer hard drive• CD-R drive• CD-RW drive• DVD drive


Display Device

• Typically a CRT or LCD monitor.

• Size defines screen area.

• Video card should meet needs of application.


Input Devices

• Keyboard

• Mouse

• Trackball

• Digitizer puck

• Light pens


Output Devices

• Pen plotter

• Laser printer

• Inkjet printers

• Inkjet plotters


Pen Plotter

• Traditional device for CAD work.

• Generates vector drawings.

• Used for large-format output.

• Produces very accurate line quality.

• Disadvantage is slow operation.


Inkjet Printers and Plotters

• Generate raster drawings.

• Used for high-quality color renderings.

• Potential disadvantages are slow operation and cost.

(DesignJet Division, Hewlett-Packard)


CAD Packages

• Types and costs vary based on features provided.

• Lower-end systems used for 2D drawing.

• More advanced software available for 3D work.


Selecting a CAD Package

• Consider product features and specific needs.• Ease of use• Hardware requirements• Product support• Warranty coverage• Specific tools in software• Cost


Types of CAD Packages

• General purpose CAD packages

• Advanced mechanical drafting and modeling CAD packages

• AEC CAD packages


General Purpose CAD Features

• Functions for drawing objects

• Automated dimensioning

• Hatch pattern generation

• Text functions and font types

• Editing functions


CAD Hatch Patterns


General Purpose CAD Features

• Layers

• Object display colors

• Linetype definitions

• Coordinate entry methods

• Methods for entering commands


General Purpose CAD Features (Cont.)

• Drawing unit formats

• Display controls

• Drawing aids

• Printing or plotting functions

• Customization options

• Data exchange methods


3D Drawing Features

• Available in more advanced programs.• Shading and rendering• Animation• Mass property analysis


Types of 3D Models

• Surface model

• Solid model


Advanced Mechanical Drafting and Modeling CAD Packages

• Designed for advanced engineering applications.

• Provide additional 3D modeling features.

• Commonly used in automated manufacturing.


Advanced Mechanical Drafting and Modeling Features

• Solid modeling tools

• Parametric modeling tools

• Automatic view generation

• Mechanical symbol libraries

• CAD/CAM functionality


Solid Modeling

• Building from primitives.

• Revolving 2D profiles.

• Extruding 2D profiles.

• Removing material.

• Sweep operations.

• Loft operations.


Extruded Solid Model


Revolved Solid Model


Swept Solid Model

(Anthony J. Panozzo)


Parametric Modeling

• Model defined based on adjustable parameters.

• Parts added must conform to existing construction.

• Model may include constraints.

• Operation verified during process.


Parametric Modeling Program

(Image Courtesy of SolidWorks Corporation)


Automatic View Generation

• Fills need to provide 2D drawings to manufacturing personnel.

• Orthographic views most common.

• Section, auxiliary, and pictorial views may also be generated.


Computer-Aided Manufacturing

• Uses CAD data in computer numerical control (CNC) operations.

• Typically used by machining centers.

• Tooling movement and speed controlled automatically.

• Design data verified before machining.


CAD/CAM Software Program

(EdgeCAM/Pathtrace)


AEC CAD Packages

• Designed for specific AEC fields.

• Special features added to general CAD tools.

• Used in both 2D and 3D drawing.


AEC CAD Package Features

• Automatic schedule generation

• Space diagram creation

• Stair generation

• Hatch pattern generation

• Wall creation

• Symbol libraries


Space Diagram Conversion


Common AEC Symbol Libraries

• Doors and windows

• Structural members

• Plumbing fixtures and fittings

• Electrical fixtures

• HVAC components

• Landscaping features


Common AEC Symbol Libraries (Cont.)

• Furniture and appliances

• Title symbols

• Construction details

• Vehicles


Door and Window Symbols


Building Information Modeling (BIM)

• Form of parametric modeling.

• Used in more advanced AEC CAD programs.

• Data stored for each construction system in structure.

• Components added alter existing structure.

• Result may be called virtual building.


Building Information Modeling Features

• Cost analysis tools

• Automatic generation of plan drawings

• Automatic schedule generation


Building Information Modeling Program

(Autodesk, Inc.)


Review Questions

1. A symbol _____ is a collection of standard shapes and symbols used in a particular CAD application.

library


Review Questions

2. A computer mouse is an example of a(n) _____ device.

input


Review Questions

3. A(n) _____ prints object lines on drawings as vectors.

A. laser printer

B. inkjet printer

C. inkjet plotter

D. pen plotter

D. pen plotter


Review Questions

4. Which of the following is not a typical feature found in a general purpose CAD package?

A. Hatch pattern generation

B. Automated dimensioning

C. Editing functions

D. Building information modeling (BIM)

D. Building information modeling (BIM)


Review Questions

5. _____ are similar to transparent drawing sheets on which you can draw.

A. Hatch patternsB. LayersC. LinetypesD. Drawing aids

B. Layers


Review Questions

6. A _____ is a solid model created by extruding a profile along a path.

A. sweep

B. primitive

C. revolution

D. union

A. sweep


Review Questions

7. Special controls called _____ are used in parametric modeling to define size and location dimensions to establish spatial relationships.

constraints


Review Questions

8. A(n) _____ is created by extruding one or more profiles along a special type of path called a rail.

loft


Review Questions

9. Which type of CAD program is best suited for automated manufacturing?

A. Building information modeling (BIM) program

B. General purpose CAD packageC. CAD/CAM programD. AEC CAD package

C. CAD/CAM program

Documents

Section 1 Introduction to Drafting Chapter 3 Introduction to CAD