Cad Guidebook: A Basic Manual for Understanding and Improving Computer-Aided Design (38 page)

6.7.4 CAD System Upgrades

One of the most demanding tasks with respect to CAD system administration is
upgrading the system. The CAD system and the network it runs on is a rather
sophisticated and specialized arrangement. Furthermore, despite its sophistica-
tion, it often has to be customized to become fully useful to users (as described
above). Therefore, there is a great deal of functionality that needs to be assessed
during upgrades. In addition to testing all the new functionality that comes with a
new release of the CAD system, one needs to ensure that all the existing func-
tions are still functional. The only way to preserve the production ready status of
the system for an upgrade is to test the software. Regardless of what has been
indicated by the CAD system vendor, each company should test the upgrade be-
fore making it widely available.

Besides the upgrade of the CAD system, administrators should also care-
fully test new releases of operating systems, computer hardware (particularly

Managing 2-D CAD 167

graphics adapters), and networking software. These all have the potential to dis-
rupt production, as well.

6.8 CHAPTER EXERCISES

1. Create a hardcopy or print of the CAD drawing created in the Chapter
5 Exercises.

2. Record the plotting process used by the CAD system. Determine if a
neutral file is created, and if so, what kind of file. Determine if the data goes
directly to the plotting device from the computer system or if it is sent via a
network.

3. Record the format or language of the data received by the plotting
device.

4. Determine if the CAD system uses a database manager driven data
management or if just file names and folders from the operating system are used.
If the database manager approach is used, record the metadata that can be used as
fields in the database program (i.e. can you search for drawings based on part
number, revision level, the person that created it, etc.).

5. Export a CAD neutral file (such as DXF or IGES) for the drawing, and
then try to import it back into the CAD system as a brand new drawing. Record
what problems appear in the re-imported copy of the drawing.

6.9 CHAPTER REVIEW

1. If a drawing in a released vault is copied for someone to study the part

but not to change it, what wording should be stamped on the copy?

Why is this important?

2. If a drawing in a released vault is checked out from the vault to be

changed what happens to the Revision Level shown in the Title Block

of the drawing?

3. What is the purpose of the ECR process?

4. What are some of the problems that typically arise from the translation

of drawings between different CAD systems?

5. Whenever drawings are translated for use by another user or customer

with a different CAD system, should a print or image file be delivered

as well? Why?

6. What are some considerations for whether CAD system software

should be installed on a local drive versus a network file server?

7

Three-Dimensional CAD

This chapter covers important concepts that need to be understood before pro-
ceeding with detailed information on 3-D CAD. If the reader is already fairly
comfortable with 3-D CAD, then one can proceed to following chapters. These
later chapters provide details on the subjects of part modeling (creating a 3-D
model of a single object or part), surface modeling (a special approach to part
modeling), assembly modeling (creating a 3-D model of a collection of parts),
and 3-D CAD management. Of course, if a concept or term encountered in the
later chapters causes problems for the reader, then refer back to this chapter.

7.1 INTRODUCTION

Up to this point, discussion of CAD systems has focused on the two-dimensional
approach. In the 2-D case, work with the CAD system is based on planar mathe-
matics. Users of these CAD systems see only the flat representation of data. The
output of the system is just drawings (whether in electronic or paper form).

Although these 2-D CAD systems have basically eliminated all drafting
and the manual production of formal mechanical drawings, they still require that
the designer (or other type of user) mentally visualize the physical object or de-
sign based on flat views. Although this is not a significant problem for simpler
parts, it can be an enormous problem when the object or assembly is complex.

168

3-D CAD 169

For instance, when the drawing is showing how to weld together 30 or 40 inter-
connected plates at a variety of angles, it can literally take hours of studying to
fully understand the design.

Clearly, the process of designing and documenting something geometri-
cally complex would benefit from a CAD system that could actually show and
manipulate three-dimensional models. For many years, this was simply not prac-
tical for industrial users due to the relatively limited power available from com-
puters (particularly mainframe computers that had to be shared with many other
users). However, throughout the 1980s and 1990s, the power of non-mainframe
computational systems expanded consistently and aggressively. Eventually (at
least by the mid 1990s), the computational power that could be afforded to each
designer was sufficient to create and manipulate 3-D models. Now, 3-D methods
can be considered the norm for mechanical design.

Table 7.1 lists some of the advantages of the 3-D CAD system. It may
seem odd that these need to be listed, but there has generally been great resis-
tance to the adoption of the 3-D CAD system in most companies. It has simply
been such a large break with previous systems that the transition was generally
disruptive. It has been disruptive to work processes since decades-old paper-
driven design methodologies have had to be changed. It has been disruptive to
productivity since there is a significant learning curve as designers have to be re-
trained, but then they slowly gain back and then exceed the 2-D work output.
And, it has been disruptive financially since the initial contracts for obtaining the
systems can be quite significant (as opposed to existing 2-D CAD systems that
are already paid for).

Finally and perhaps most importantly, it has been disruptive at a personal
level since the 3-D CAD system is more demanding of the user. They must be
comfortable with following the logic and organization of the software’s methods.
Unlike 2-D CAD, where virtually any particular method of construction could be
followed as long as the final product (the drawing) looked right, 3-D CAD users
must create a “real” mathematical model. These models are expected to be used,
re-used, and tweaked over time. In the 3-D CAD system, more particular meth-
ods of construction must be followed. Some methods could be disastrous in the
future, while other methods are robust and powerful. The trick, in a sense, is to
think like the software, and to maximize its strengths and minimize its weak-
nesses. Many designers, particularly those who have done 2-D work for a long
time, are not prepared for this level of involvement with the software. Hopefully,
the following chapters in this work will be helpful in minimizing the risks for
these users.

There are some important issues for users to consider at the start. First, 3-D
CAD is not really that difficult. Most people able to do design work can learn
how to do 3-D CAD effectively, at least if they keep practicing. Second, there is a
fair amount of jargon and assumed knowledge hidden in the 3-D CAD systems.

170 Chapter 7

TABLE
7.1

Advantages of 3-D CAD

Visualization

Automated
drawings

Geometric
properties

Interference

checking

Improved

quality

“True” design
reviews

The most basic advantage of 3-D CAD is that the designer can really
see the design. There is no need to study the views on a drawing.
And, 3-D CAD provides a means of navigating or dynamically
viewing 3-D models. This means the designer can view it from any
angle and rotate it any direction. Usually, the designer can also
make it translucent, cut open the model, etc.

Since drawings are often still needed to communicate designs with

suppliers and customers, 3-D CAD is used to automatically create

the geometric entities in drawings. Once a user indicates the view-

ing angles (Front, plane, datum, etc.), 3-D CAD can view object,

remove or process hidden lines, and then create drawing views.

3-D CAD meets or beats times for drawing new geometry created

in 2-D CAD.

Once 3-D model is created, it can be analyzed in many ways that are

not possible with 2-D CAD. For instance, the volume of a properly

created 3-D model can be easily calculated. Assuming material of

part is known, the weight can then be calculated. Even if the 3-D

model is an assembly of many different materials, the 3-D CAD

system can still account for this and give a very accurate weight.

Distances in 3-D models can also be measured in sophisticated

ways (3-D point-to-point, points-to-lines, points-to-edges, sur-

faces-to-points, lines-to-lines, etc.), so designs can be more refined

and understood than in 2-D.

Once a 3-D model is created, it is possible to have the 3-D CAD

system automatically determine if models or pieces of models

interfere.

3-D CAD provides easier transition to the creation of analytical mod-

els (for predicting failure). Drawings that are automatically created

from 3-D models have fewer chances for geometry errors. Isomet-

ric views can be produced easily; an isometric view on a drawing

is helpful for the drawing reader to quickly assess what the draw-

ing is attempting to show; reader can search for the proper level of

detail and understand the drawing more productively and make

fewer errors in interpreting.

Design reviews are “high level” meetings that discuss the state of a

product design (including designers, engineers, managers, custom-

ers, marketing, manufacturing personnel). They are meant to make

sure that the design is meeting requirements. Although they can be

done with drawings, there is very limited feedback since attendees

are forced to imagine the product design state (often non–engi-
neering personnel are not adept at studying drawings). This prob-
lem practically evaporates when viewing a projected image of a 3-
D model. Feedback is plentiful.

3-D CAD 171

TABLE
7.1

Continued

Intelligent

models

Standardiza-
tion

Associativity

Integrated

product

development

3-D modeling software generally encourages designers to include de-
sign intent. This may take the form of creating parametric relation-
ships, entering equations, family tables, constraints, etc. This can
allow a generic part model to generate related parts automatically.
It might also encode into a 3-D model which dimensions or param-
eters are most important in the design.

Although 2-D CAD may have a means for storing and organizing
standard geometry, once it is placed into a drawing, there is typi-
cally no tracking of reuse. 3-D CAD can keep a record of the times
the standard 3-D part models are used in an assembly.

3-D CAD can keep track of individual geometric entity’s relation-
ships to each other. Using this associativity feature, when the 3-D
model is revised, the geometry and dimensions in the 2-D drawing
can automatically change. Relationships can also drive changes in
an assembly or analysis model based on a part change.
With capabilities such as visualization, associativity, and intelligent
models, it becomes much more realistic to create interdisciplinary
teams for product development. Disciplines that might be repre-
sented on such a team would be manufacturing engineering, mar-
keting, process planning, purchasing, system integration, etc.
Although these groups can be used on a team with 2-D CAD, in
3-D CAD these groups can very easily integrate the state of the
design with their disciplines (just by looking at and manipulating
the 3-D models).