The term “design” has many connotations.
They can range from industrial designers to
high structural load engineering designers.
A few of these will be summarized in order
to highlight that different designer skills
are used to meet different product requirements.
Essentially it is the process of devising
a product that fulfills as completely as possible
the total requirements of the user, and
at the same time satisfies needs in terms of
cost-effectiveness or ROI (return on investment).
It encompasses the important interrelationship
practical factors such as shape, material
selection (including unreinforced and
reinforced, elastomers, foams, etc.), consolidation
of subparts, fabricating selection, and
others that provide low cost-to-performance
products.
Product design is as much an art as a
science. Recognize that a successful design
is usually a compromise between the requirements
of product function, productibility,
and cost. Basically design is the mechanism
whereby a requirement is converted to
a meaningful plan. Design guidelines for plastics
have existed for over a century.
With plastics to a greater extent than other
materials, an opportunity exists to optimize
product design by focusing on material composition
and orientation to structural member
geometry when required. The type of designer
to produce a product depends on the
product requirements. As an example in most
cases an engineering designer is not needed
because the product has no major load requirement.
All that is needed is experience
and/or a logical evaluation approach based
on available material and processing data.
This practical approach is the least consumer
of time and least expensive.
Design Technology
It is the prediction of performance in its
broadest sense, including all the characteristics
and properties of materials that are essential
and relate to the processing of the plastic.
To the designer, an example of a strict definition
of a design property could be one that
permits calculating product dimensions from
a stress analysis. Such properties obviously
are the most desirable upon which to base
material selections.
However, like with metals, there are many
stresses that cannot be accurately analyzed.
Hence one is forced to rely on properties that
correlate with performance requirements.
Where the product has critical performance
requirements, such as ensuring safety to
people, production prototypes will have to
be exposed to the requirements it is to meet
in service.
In plastics, these correlative properties, together
with those that can be used in design
equations, generally are called engineering
properties. They encompass a variety of situations
over and above the basic static strength
and rigidity requirements, such as impact, fatigue,
flammability, chemical resistance, and
temperature.
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