Slides in this set
What is a PDS and why write one
A product design specification (PDS) is a document
which sets out fully and in detail exactly what will be
required of a product, before it is designed. Many
companies do not work to such formal specifications, but
as a result they are not fully in control of what they
produce. PDSs are essential.
A PDS does not just help the people who design and
make the product. Those who eventually use it also
benefit. Consumers' judgements are all too often
overlooked by engineers, but people think critically about
the products they buy. They may take an interest in
design or engineering for its own sake. They certainly
will not hesitate to criticise a product if it does not do,
efficiently and reliably, what they expect it to. A PDS is
therefore also an analysis of what the market will
demand of the product.…read more
A PDS specifies a problem, not a solution. A
PDS does not pre-empt the design process by
predicting its outcome. Rather, it defines the task
by listing all the conditions the product will have
to meet. This can involve a good deal of
research, into market conditions, competing
products, and the relevant literature including
patents. When you write a PDS, you are defining
something that does not yet exist. But for
practice at thinking this way, it can help to look at
an existing product and work out what its PDS
A PDS has to be a written document, but it does
not need to be engraved in stone. It can be
changed. As a rule, the design follows the PDS.
But if the emerging design departs from the PDS
for some good reason, the PDS can be revised
to accommodate the change. The important thing
is to keep the PDS and the design in
correspondence throughout the design process.
In this way, the PDS ends up specifying not just
the design, but the product itself.…read more
This section give detailed advice on writing a PDS under
the 29 headings listed below. It is therefore a good idea
to write your PDS under these headings, leaving out only
those that clearly do not apply.…read more
Performance questions are usually the first to occur to
engineers, so make these the first you answer.
· What exactly is your product going to do?
· How fast will it run?
· Constantly or intermittently?
· Under what loads?
· For how long?
Remember, the more complex the product, the greater
the likelihood of needing to specify ranges of values,
rather than single, fixed values.…read more