Cad Guidebook: A Basic Manual for Understanding and Improving Computer-Aided Design (4 page)

Boboc

145.
Implementing
Concurrent
Engineering
in
Small
Companies,
Susan
Carlson
Skalak
146.
Practical
Guide
to
the
Packaging
of
Electronics:
Thermal
and
Mechanical
Design

and
Analysis,
Ali
Jamnia

147.
Bearing
Design
in
Machinery:
Engineering
Tribology
and
Lubrication,
Avraham

Harnoy

148.
Mechanical
Reliability
Improvement:
Probability
and
Statistics
for
Experi-mental

Testing,
R.
E.
Little

149.
Industrial
Boilers
and
Heat
Recovery
Steam
Generators:
Design,
Applications,
and

Calculations,
V.
Ganapathy

150.
The
CAD
Guidebook:
A
Basic
Manual
for
Understanding
and
Improving
Computer-

Aided
Design,
Stephen
J.
Schoonmaker

151.
Industrial
Noise
Control
and
Acoustics,
Randall
F.
Barron

152.
Mechanical
Properties
of
Engineering
Materials,
Wolé
Soboyejo

153.
Reliability
Verification,
Testing,
and
Analysis
in
Engineering
Design,
Gary
S.
Was-

serman

154.
Fundamental
Mechanics
of
Fluids:
Third
Edition,
I.
G.
Currie

Additional
Volumes
in
Preparation

HVAC
Water
Chillers
and
Cooling
Towers:
Fundamentals,
Application,
and
Opera-
tions,
Herbert
W.
Stanford
III

Handbook
of
Turbomachinery:
Second
Edition,
Revised
and
Expanded,
Earl
Logan,
Jr.,
and
Ramendra
Roy

Progressing
Cavity
Pumps,
Downhole
Pumps,
and
Mudmotors,
Lev
Nelik

Gear
Noise
and
Vibration:
Second
Edition,
Revised
and
Expanded,
J.
Derek
Smith

Piping
and
Pipeline
Engineering:
Design,
Construction,
Maintenance,
Integrity,
and
Repair,
George
A.
Antaki

Turbomachinery:
Design
and
Theory:
Rama
S.
Gorla
and
Aijaz
Ahmed
Khan

Mechanical
Engineering
Software

Spring
Design
with
an
IBM
PC,
Al
Dietrich

Mechanical
Design
Failure
Analysis:
With
Failure
Analysis
System
Software
for
the
IBM
PC,
David
G.
Ullman

Preface

It was a black day, indeed, when I walked into my most recent place of em-
ployment in south-central Pennsylvania about six years ago. I had just spent 11
years lost in the “other-world” of software development (writing commercial and
in-house analytical software for the design of all kinds of gas compression equip-
ment). I had avoided CAD (computer-aided design) like an extroverted skunk go-
ing door-to-door trying to sell the benefits of aroma therapy. CAD was just for
making those drawing thingies I had heard about. But on this black day, I had
agreed to lead the company’s full-blown implementation of that “solids” stuff,
and the company’s designers were as much T-square huggers as I was a tree-
hugger (did I mention that I got my engineering degree in Massachusetts?).

Well, the Lord works in mysterious ways, and after about three years, the
designers were humming away at 3-D CAD and trying to convince middle man-
agers that it really was the way to go. And those same designers had actually not
beaten me to a pulp! Instead, they taught me how things worked in the real world.
Together we pumped out a whole bunch of new product, and now there are some
construction sites out there that are hopefully benefiting from our little experi-
ment with CAD.

Since I had previously written a book on ISO 9001 (that’s another long
story), I figured I may as well share what I had learned about CAD with the rest
of the world. I guess I have some teacher gene that says I must share what I know

iii

iv Preface

for the betterment of society. I do hope this book is helpful to you, and with any
luck, you will learn to stop worrying and learn to love your CAD system. And
even though little fun is to be had at most workplaces anymore, I hope you will at
least find that 3-D CAD can be fun.

Of course, this really important book that I read every day has a story that
ends with the moral “of those to whom much is given, much is expected.” I, for
one, certainly have been given much. First, I have been blessed to have been born
and raised in the United States of America. It’s not a perfect country, but there is
no other nation in the history of the world that comes close to its ability to let
people like me breathe free and find their own best way to serve. Secondly, I have
been given the best family a man could hope and pray for. Sharon, Melissa, Jen-
nifer, Michael, and Christina were kind enough to let me take the time to do an-
other book. Thanks, guys.

I must express my thanks to some of those folks that helped me learn about
this CAD-thingy. Thanks especially to Doug Beckner, Vince Bernabe, and Mike
Miller at Grove. I think they actually understood what I was talking about! We
implemented the I-DEAS®
Master Series CAD system from SDRC (now EDS),
so I thank them for their support over the years, too. In particular, thanks to their
tech support people under Ron Hickman, Barry Ratihn of their post-sales group,
and Rick Miller of their training staff. I also thank Grove’s IT department and its
latest CAD-burdened victim (I mean employee), Brett Cox. I am not positive, but
I think CAD is no good if there are no computers to run it on. Finally, I thank my
boss, Ralph Kegerreis, who actually let me get away with all of this. Thanks,
Ralph.

Well, there you have it. Have fun.

Steve Schoonmaker

Contents

Preface iii

Chapter 1 Introduction 1

Chapter 2 Computer Hardware Basics 6

Chapter 3 Computer Software Basics 45

Chapter 4 Drawings and 2-D Design 71

Chapter 5 Two-Dimensional CAD 106

Chapter 6 Managing Two-Dimensional CAD 145

Chapter 7 Three-Dimensional CAD 168

Chapter 8 Part Modeling 188

Chapter 9 Surface Modeling 224

v

vi Contents

Chapter 10 Assembly Modeling 242

Chapter 11 Managing Three-Dimensional CAD 263

Glossary 285

Bibliography 317

Index 319

1

Introduction

This work is intended to provide a basic understanding or foundation for working
with a CAD system. Although there have been many acronyms over the years
(CADD, MDA, etc.), in this work CAD is to refer to Computer-Aided Design.
Computer Aided-Design, in turn, is assumed to mean various types of tasks re-
lated to product design. Some of these tasks would be preliminary design and
layouts, design calculations, detailed design, creating 3-D models, creating draw-
ings, releasing drawings, as well as interfacing with analysis, marketing, manu-
facturing, and end-user personnel. Although this is a broad array of tasks, all of
them would be affected by the currently available CAD systems.

1.1 SCOPE AND INTENDED AUDIENCE

Since this work is intended to provide a basic understanding, it is not going to be
sufficient for a particular designer or engineer to be proficient with a particular
CAD system. Only an appropriate CAD training program is going to be able to
provide this proficiency. However, this work would be very effective in conjunc-
tion with such a training program. The information in this work can make it eas-
ier to understand why the CAD system operates in a certain fashion. This
understanding then reinforces the knowledge being learned and shortens the
overall learning curve.

1

2 Chapter 1

This work is also not a complete source of information on specific de-
signer-related activities such as creating complete drawings or Bills of Material
(BOMs). However, even those who have never seen or worked with drawings,
prints, or BOMs before will be able to follow the information presented. This can
be most valuable to those outside of design and engineering that need to support a
CAD system (such as Information Technology (IT) professionals). For practicing
designers and engineers, they must refer to their own company procedures or
other works to complete their tasks for creating and fully documenting their
designs.

Similarly, the information on CAD computer systems technology may be
oversimplified for IT professionals. They would typically be quite familiar with
the basic computer knowledge presented. Even so, some of the computer systems
information is specifically relevant for CAD software, and IT professionals who
have not dealt with CAD software before would certainly benefit from the infor-
mation. Although designers and engineers may not be familiar with the computer
systems information, they should have no trouble understanding the level of de-
tail presented.

For better or worse, the information presented by this work is heavily
geared toward mechanical drawings and mechanical design and engineering.
This activity is probably the most prevalent design activity with respect to the
manufacturing sector, so it may be the most prevalent use of CAD systems. Civil
engineering (or A/E/C) aspects of CAD have a number of similarities with me-
chanical CAD, so much information presented in this work would probably still
be relevant. However, users of CAD for graphics arts or electrical engineering
activities may find it is weighted too heavily toward mechanical design.

1.2 APPLICATION

CAD systems have been developing and advancing for decades, and yet they
show no sign of becoming completely mature. This is particularly true because of
the expanding power and usefulness of 3-D models and their ability to replace
and/or enhance drawings. CAD systems are also expanding in their influence
over the business of product design and manufacture. Computer systems that are
capable of dealing with the demands of CAD are becoming almost ubiquitous;
therefore, the opportunities to leverage the CAD system’s valuable information is
expanding beyond a traditional design and engineering environment. Integration
of CAD systems and/or data with the Internet (or more specifically the World-
Wide Web) is certainly a sign of this increasing influence, and this trend seems
certain to continue.