Copyright Goodheart-Willcox Co., Inc.
48 Engineering Fundamentals
Renderings are full-color drawings that show
what the object will look like in a given light. See
Figure 3-9. These can be hand-drawn or computer-
generated renderings.
Detail drawings are technical drawings that
accurately communicate size and shape. They
usually include specifi c dimensions for others
to see.
Three-dimensional (3-D) models can be
made by hand out of products like clay, plas-
tic, wood, and foam. They can also be drawn
using 3-D computer-aided design (CAD) soft-
ware. Designers use CAD software to create
drawings in order to communicate solutions to
design problems. Rapid prototyping machines
are used to create 3-D models. Equipment using
computer numerical control (CNC) converts the
CAD models into 3-D shapes. Computer-aided
manufacturing (CAM) software converts the
CAD drawings to machine tool paths. Tool paths
are the paths or tracks that the tool follows.
Picture an engraving tool cutting your name
into a brass plaque for an award you have won.
The cutter bit will scratch your name into the
brass similar to the way you write your name
with a pencil. The letters of your name become
the tool path.
See Workbook Activity 3-5 to learn how
to draw the best idea to communicate the
solution.
Engineers might fi nd during the solution
creation stage that none of their ideas actually
solve the problem or that none of the ideas are
feasible. They may also discover completely new
ideas or ways to improve on current ideas. They
may fi nd it necessary to move back to the idea
generation step. They may even have to rede-
fi ne the problem or reevaluate the criteria for the
solution.
Test/Analysis
Once the best solution has been chosen and
communicated, it is time to test and analyze that
solution. There are many ways to test solutions.
Engineers are responsible for selecting the test(s)
that best evaluate their solution against the stated
criteria. For example, it is critical to test the aero-
dynamics of a new wing design in a wind tunnel,
but there would be no reason to use a wind tunnel
to test a new keyboard design.
Where possible, computer simulations are
used for testing because they take relatively little
time and money to set up and run, but much can
be learned. Picture a 3-D computer simulation of
the operation of a new drive linkage for a moun-
tain bike. Computer simulations show if the parts
fi t together properly, if there is any interference
between moving parts, and the speed at which
the bike moves in a given gear when the pedals
are moved at a given speed. Tremendous knowl-
edge can be gained without having to invest the
time and money to actually build the bike.
Prototypes are also used in testing. Prototypes
are physical models of a fi nal product or some
aspect of a product. Prototypes can be made
from the material that will be used for the fi nal
product or of another material like foam or clay.
See Figure 3-10.
Goodheart-Willcox Publisher
Figure 3-9. 
Renderings show the designs in a given light.