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Exploring Drafting
An object drawn in CAD can be manipulated
in a variety of ways, making it unnecessary to
draw the object again.
Dimensions and text can be added to a
CAD drawing by selecting the appropriate
command or function and entering the required
information. The drafter can defi ne the text size,
style, and orientation as needed. CAD functions
for creating text and dimensions are discussed
later in this text.
After a CAD drawing is completed, it can
be output in a number of ways. CAD drawings
are typically printed on a plotter, Figure 7-5.
Inkjet plotters are most commonly used to
produce CAD drawings. CAD drawings may
also be output to a printer, such as a laser printer.
CAD drawings may also be converted
to an appropriate fi le format for electronic
viewing in another program. For example, a
drawing may be posted by a fi rm on a website
for clients or for another engineer working
on the project. If the fi le is sent via e-mail to
a client, the client can typically download the
viewer software needed to display the fi le.
Regardless of the drawing and production
methods required, CAD programs offer a
size. Coordinate entry, scaling, and other types
of drawing functions in CAD programs are
discussed in this chapter.
How CAD Works
A CAD drawing project starts with the
generation of a geometric model of the
proposed design. The base outline or profi le
of the design is created fi rst and then features
are added. CAD models are created in 2D or
3D form, depending on the type of program
being used and the purpose of the project.
Instructions are given to a CAD program
through the use of commands. Commands
can be picked from “ribbon” or “command
manager” tabs, selected from pull-down menus,
or entered at the keyboard. See Figure  7-4.
Toolbars and palettes may also be available for
selecting commands. A typical CAD software
interface normally provides a number of ways
to execute commands and functions.
Once objects are drawn, they can be altered
as needed. For example, an object can be
moved, rotated, copied, deleted, or mirrored.
The evolution of computer technology and
electronic communication has had a major
effect on the way drawings are made and
presented. Not long ago, manual drawings
were the primary means of communicating
manufacturing information to trade workers.
Today, drawings are created with computer-
aided drafting programs and distributed
electronically. They are used by workers to
program computer-controlled machine tools.
Computers then interpret the information
and manufacture parts. This is accomplished
through various phases of communication—
including interaction between the drafter and
the computer and the computer and a machine.
There are literally hundreds of CAD
software programs that have been used to
design products for industrial use. Computer
animation programs make it possible to
communicate an entire design of a product
before it is manufactured or built. Internet
technology makes it possible to send, receive,
evaluate, and modify drawings in a very short
period of time.
When compared to manual drawing
techniques, CAD tools have made it much
simpler to communicate information. However,
it is important to understand that as with other
communication tools, CAD is only a tool. The
same drawing skills, visualization techniques,
and concepts practiced in manual drafting must
be understood in order to use CAD accurately
and successfully.
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