Biomedical Engineering Reference
In-Depth Information
birth
death
time
Figure 1.1
The classic life cycle bathtub.
1.2 The Design Life Cycle
People like to talk about the life of a design. To have a life means something has to be brought
to life and then die; clearly this is a little too anthropomorphic for comfort. But the idea of
a cycle is very important and the product's “conception,” “birth,” and ultimate “end of life”
are very pertinent to the designer. In the past the cycle was only concerned with the time to
bring new versions to market (revision cycle). Nowadays we consider the whole cycle from
manufacture to disposal for obvious environmental reasons. Hence we have two cycles to
consider: revision cycle analysis and life cycle analysis . To avoid confusion between the old
and the new, we will use these two terms from now on.
Revision cycle analysis is concerned with keeping products and services “up to date,” and this
is usually reflected by sales figures. A classic bathtub curve describes this cycle ( Figure 1.1 ).
At the beginning a new design generates new interest and the sales grow. Eventually these
sales plateau as market penetration is reached: consumers get bored, new competitors come
along, or there is no one left to sell to. Hence this design's life has ended. To carry on with
this version would be silly to say the least. Hence designers need to plan revisions into the
process to maintain the sales plateau ( Figure 1.2 ). It is important to understand why a design
is never finished … it goes on and on, continually improving, continually getting better. In
quality management this is called a continual improvement process . It is clear that unless the
designer is embedded into the discipline into which their design will reside all will fail. We
must keep in touch with the end-user . We shall see, later, that postmarket surveillance is an
essential part of this process.
Life cycle analysis has grown in popularity since we all became aware of our environment. The
days have gone when any designer can just ignore waste and the consequences of waste. Many
products now must have carbon footprint assessments. But as designers we must all be aware of
our effects on the environment; the medical devices industry is not immune from this requirement.
We will see later that bringing together a design team enables waste to be minimized.
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