Cad Guidebook: A Basic Manual for Understanding and Improving Computer-Aided Design (5 page)

What this means for this work is that as soon as it is printed, it may be out-
of-date. Fortunately, the author feels that the basic theory and application of CAD

Introduction 3

systems will not change that drastically. Even as the systems become more capa-
ble, much of the foundation presented in this work will still be relevant. The basic
processes and problems that are found in design and engineering will still remain,
and the approaches of CAD to solving these problems will probably be the same
as well.

1.3 ORGANIZATION

This work is organized to allow most chapters to be read independently. If there
are concepts that build on a previous chapter’s
information, the
reader should be
able to locate that information by referring to the section headings.

This work is broken into 3 general parts. The first part (Chapters 2 and 3) is
geared toward basic information on computer systems that is most relevant to a
CAD platform. Chapter 2 covers computer hardware and chapter 3 presents in-
formation on computer software.

Chapters 4, 5, and 6 concerns drawings and CAD systems that support
drawings. Chapter 4 shows the drawings themselves and how they are used to
design products in a 2-D (two-dimensional) medium. Chapter 5 illustrates CAD
systems that actually automate 2-D design and the production of drawings. Chap-
ter 6 explains the management of a 2-D CAD environment.

The final part of the work is geared toward 3-D (three-dimensional) CAD.
The author’s primary experience as a programmer, user, and manager of CAD
systems is with 3-D CAD systems, so this part of the work is the most extensive.
These systems are the latest and most powerful. Of course, they also demand the
most from the users and administrators. Considering the importance of the these
systems, this part of the work may be the most useful to the reader. Chapter 7
introduces the topic of 3-D CAD; this chapter should be read if any other chapter
on 3-D CAD is of interest to the reader. Chapter 8 refines 3-D CAD with respect
to part modeling (creating standard, solid models). Chapter 9 explains 3-D CAD
with respect to surface modeling (creating more specialized, free form models).
Chapter 10 covers assembly modeling (combining part models into a sort of
group 3-D model). Finally, Chapter 11 covers the management of a 3-D CAD
environment.

1.4 AUTHOR’S BACKGROUND

The author of this work has had a somewhat varied background leading to a level
of expertise with CAD systems. The first experience came in the form of com-
puter programming for CAE (computer-aided engineering) software. The soft-
ware he helped develop and manage was used for the design and analysis of
turbomachinery (pumps, compressors, turbines, and their constituent compo-

4 Chapter 1

nents). This software was sold under the name COMIG®
from the former North-
ern Research and Engineering Corporation (or NREC). This software was
developed at a time that computer graphics (2-D and 3-D) was just becoming
standardized, so most of the CAD graphics experience was obtained in a rather
“early” environment. Having experience with very large software development
projects was also highly beneficial in understanding how software really works
and how it is really used (particularly in the engineering analysis community).
Hopefully, a sensitivity to the special needs of the engineering analysis field is
apparent in this work.

The next experience was as a specialized engineering analyst in the com-
mercial gas compression market. This included creating, supporting, document-
ing, and verifying of in-house software for reciprocating gas compressors and gas
engines. This was at the former Engine Process Compressor Division of Dresser-
Rand. This experience was valuable in seeing how engineering work supports ac-
tual product development and manufacturing (as opposed to the research environ-
ment). Regarding the use of 2-D CAD, Bills of Materials, and Routings, Quality
Control was observed. A unique aspect of this experience was being responsible
for the development and execution of processes to verify and validate design-cen-
tric computer software for the ISO 9001 quality standard (which had become a
vital issue to the company). In conjunction with that experience, another pub-
lished work, ISO 9001 For Engineers and Designers, was published by McGraw-
Hill and professional development courses were directed by the author for ASME
International. Again it is hoped that a healthy respect for quality systems and
practical manufacture is reflected in this work as well.

Subsequently, the author was the project leader for the implementation of a
3-D CAD based design and engineering environment for a mechanical equipment
manufacturer. This manufacturer was Grove Worldwide, which designs and man-
ufactures mobile hydraulic cranes and aerial work platforms. This company had
been using mainframe 2-D CAD for about 15 years, and they had made the deci-
sion to change to a client/server network with fully associative 2-D and 3-D soft-
ware. The full implementation took approximately 4 years to complete. A design
team-based management style was implemented in the same time frame as 3-D
CAD, and the net effect of these changes was a very significant reduction in the
time to completely design and put into production large cranes (without the use
of more personnel).

1.5 CAD IMAGES

The CAD system used in conjunction with the development of this work was
the I-DEAS Master Series™ version 7.3 from SDRC®
(Structural Dynamics

Introduction 5

Research Corporation). It was running on the IBM®
RS/6000

®

43P-140 with
AIX®
version 3.4. The images were “captured” with the Xwindows screen dump
utility and then imported into ImageMagick©
version 5.2.4 00/10/01 © 2000
ImageMagick Studio (running on the same IBM platform). In ImageMagick, im-
ages were changed to grayscale, cropped, annotated, etc. and then converted to
JPEG files.

2

Computer Hardware Basics

2.1 INTRODUCTION

In order to fully master a CAD system, it is important to understand how a com-
puter functions. The intent here is not to become a expert in computer technol-
ogy, but to build a foundation. With this foundation, a good CAD user or a CAD
manager can hopefully evaluate systems and create appropriate design processes.
Particularly with the wide proliferation of very capable 3-D CAD systems, it is
essential to know how the CAD software is going to interact with the computer
hardware; 3-D CAD is one of the most demanding applications available to run
on computers. Understanding how the software is trying to utilize the computa-
tional resources can make the difference between a productive design process and
one that provides little benefit at all.

A basic understanding of computer systems allows designers and engineers
to make proper trade-off’s in utilizing available computer resources. If a designer
knows about graphics accelerators, he or she can tell if a low-end PC can handle
a particular task. If the designer knows about how files are written and stored on a
computer, he or she can tell what it will take to translate the model to other for-
mats or to other types of computer systems. If the designer knows something
about computer networks, he or she will be able to tell how long it will take to

6

Computer Hardware Basics 7

transfer a design’s files to other computer systems. These situations are common
in everyday design and engineering practice. CAD plays a vital role in many
aspects of design and engineering. Furthermore, designers and engineers that use
CAD are expected to understand how to maximize the benefits of CAD, and
understanding the computer systems themselves is an important ingredient in
this process.

The remainder of this chapter presents a very basic background in com-
puter hardware. Hardware refers to the physical components of a computer sys-
tem. However, it must be understood that the computer hardware is of little value
without software. Software is the computer programming that runs or “executes”
on the hardware. A basic background in computer software is presented in the
next chapter.

The hardware is often closely tied to the software that is running on the
computer, and in particular, on software called the operating system or OS.
Sometimes the combination of the hardware and software is referred to as a plat-
form. For example, two common platforms are the UNIX®
platform (the Unix
operating system combined with a workstation) and the Windows®
platform (the
Windows operating system combined with a personal computer (PC)).

2.2 THE SYSTEM

Figure 2.1 shows a very basic model of a typical computer system (such as a PC
or a workstation) that would run a CAD program. The PC and workstation plat-
forms have these same basic components. Although in the 1970s, 1980s, and
1990s, it would have been appropriate to consider a mainframe and its terminals,
today there are few mainframes running CAD programs.

As can be seen from Figure 2.1, the main components of the platform are
as follows:

• Central Processing Unit (CPU)

• memory

•storage

• peripherals (such as monitor, keyboard, and mouse)

All these components are connected within the computer via an electronic
highway called a bus so that they can communicate at a very rapid rate (millions
or even billions of signals per second). Although the basic components are going
to be somewhat familiar to most readers, there are some common misconceptions
concerning some of these components. The biggest problem is probably the dis-
tinction between memory and storage; this issue is discussed shortly.

8 Chapter 2

FIGURE
2.1

Basic hardware/components of a CAD platform.

2.3 CPU

The CPU can be easily referred to as the master of the system. It is an integrated
circuit (IC or “chip”) that really manages the data amongst the components. All
the other components, therefore, are designed around the CPU, and the CPU usu-
ally has the most obvious effect on the performance of the computer. These de-
vices have been developing and advancing for decades now, and many classes or
types of CPUs have come and gone. Although mainframe computers were once
built around the CPU (to be shared by hundreds of users via terminals) today
each user normally has a CPU dedicated to their use within their personal system.

There are only a handful of vendors that produce CPUs that would typi-
cally be used for CAD software. Therefore, there are only a few basic computer
systems that CAD users will generally come in contact with. Probably the most
popular CPUs (for all applications) are made by Intel®. Intel CPUs have had
names such as 8086, 80286, 80386, 80486. After this series of CPUs, a series of
Pentium®
chips were made (Pentium, Pentium II, Pentium III, etc.), and then the
Itanium®. Another popular series of CPUs are made by Motorola®. Their chips
have had names such as 68000, 68010, 68020, 68030, 88000, etc. These chips
were the basis for the Apple®
Macintosh

®

(Mac) computers. The remaining
CPUs found in CAD systems would be from complete computer systems manu-

Computer Hardware Basics 9

facturers such as IBM, Hewlett-Packard®
or “HP

®,” Sun Microsystems™, etc.
Their chips would generally be considered “proprietary” since other computer
systems makers generally do not use them. This is in contrast to Intel and Motorola
which do not provide complete computer systems. Another source of CPUs would
be from “clones.” These chips are made by companies other than Intel or Motor-
ola, but they are functionally equivalent or compatible with the original chips.