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As
a useful supplement on design, David Norman, an American psychologist,
urges designers to consider the manufacturing and assembly errors that
do occur, and make them easier to correct. This should be done at the
design stage. He further urges designers to take a wider view of users:
"Think of an object's user as attempting to do a task, getting there
by imperfect approximations." So it's the usefulness of the product
in its wider context that counts.
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COMPLEXITY OF DESIGN
Boothroyd
and Dewhurst have also suggested a measure for the assessment of design
complexity. They use three factors: the number of parts (Np), the number
of types of parts (Nt), and the number of interfaces between parts (Ni).
First, the numeric value of each of these factors is determined by addition.
Then, the factors are multiplied and the cube root taken. This yields
the design complexity factor. Note that reducing the number of parts usually
also reduces the number of interfaces, which are points at which defects
and difficulties are most common. Also, reducing the number of types of
part has a direct impact upon inventory management and quality.
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