Copyright Goodheart-Willcox Co., Inc.
Chapter 3 Engineering Design 49
Prototypes can simply be the outside shape of
an object at full scale, scaled down, or scaled up to
meet the needs of the test. Picture a full-scale clay
model of a new sports car painted to look like the
fi nished product. A model like this can be tested in
a wind tunnel for aerodynamics or shown to poten-
tial customers to test the market for such a car.
Sometimes full-scale working prototypes are
made to test all aspects of a new design. For exam-
ple, a new offi ce chair can be made as if it came off
the production line. The prototype could be given
to people in offi ces, where it would be used in its
real environment. The people who use the chair
then provide feedback to the engineers about what
they liked or disliked about the chair.
CNC lathes, routers, mills, and other equip-
ment are used to cut prototype parts out of solid
pieces of materials like wood and metal. Designs
are created using CAD software, and the parts
are made by the machines. Parts that might have
taken hours or days to make using conventional
means can now be made in a matter of minutes.
Rapid prototyping is increasingly popular
because it is a fast and affordable way to move
from design to prototype. The term rapid proto-
typing refers to a variety of processes, but three-
dimensional (3-D) printing is the most popular.
Three-dimensional printers build solid models
by adding many thin layers of material until the
entire shape has been created, Figure 3-11.
Goodheart-Willcox Publisher
Figure 3-10. 
This prototype can be used to test the new design of the
locker.
Figure 3-11. 
Rapid prototyping
machines build models
layer by layer until desired
shapes have been created.
Stratasys, Inc.