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Chapter 3 Engineering Design 45
such as size, cost, and quality. These are the
design requirements or constraints of the design.
Understanding the constraints on the design
is part of the problem defi nition stage. The
constraints and background information must be
fully understood before the engineer can move
on to the idea generation stage.
See Workbook Activity 3-1 to identify prob-
lems, criteria, and constraints.
Idea Generation
In the idea generation stage, engineers try
to come up with as many different ideas or solu-
tions as possible without regard for evaluating
them. The process of generating ideas is called
ideation. There are no wrong answers at this
stage. The most important thing is to come up
with as many ideas as possible. There is a direct
link between the number of ideas generated at
this stage and the quality of the fi nal product
of the design process. Generating a great idea
starts with an open mind and the willingness to
think outside the box. As more ideas are gener-
ated, a wide variety of solutions are available
to the engineer in the next step. Increasing the
number and variety of ideas increases the likeli-
hood that one of them will be a good solution.
Once a wide variety of ideas have been gener-
ated, each will be evaluated individually in the
solution creation stage.
While there are numerous techniques for
ideation, brainstorming is one of the most
commonly used. Brainstorming involves generat-
ing ideas in order to develop solutions. This tech-
nique can be done by an individual, but is more
commonly and more effectively done in groups.
A group of people, preferably of diverse back-
grounds, is brought together and given a problem.
One person is selected to keep a record of ideas.
Math
Ratios and Scale
Objects are often too large to fit on available paper, or they are too small to be seen at their normal size
on paper. Drawings can be scaled up or down in order to meet the needs of the reader. The concept of scale
is something you will need to understand in order to create sketches and drawings of designs. A scale is a
means of communicating the size of the design on paper relative to the size of the actual designed object.
Scales are communicated in ratios.
Imagine you are designing a new four-wheeler, and you need to communicate your drawing on standard
8 1/2″ × 11″ printer paper. The four-wheeler you have designed measures 50″ tall and 60″ long. You could
scale it down by a factor of ten for printing. A scale of ten to one can be shown as the ratio 10:1. This means
each inch on the paper is equal to 10″ for the real design.
10:1 = 50:5
10:1 = 60:6
50″ scaled by a factor of ten equals 5″. 60″ scaled by a factor of ten equals 6″. Therefore, your design of
the 50″ × 60″ four-wheeler shown at a scale of 10:1 is shown as 5″ × 6″.
For the following problems, use ratios to scale the design up or down to fit on standard 8 1/2″ × 11″
printer paper.
1. A 72″ × 60″ oven.
2. A 1″ × 2″ digital music player.
3. A 4 ″ × 8″ office phone.
4. A 52″ × 36″ television.
5. A 60″ × 84″ bookshelf.