Page 26 - Biomedical Engineering and Design Handbook Volume 2, Applications

MEDICAL PRODUCT DESIGN 5

1.2 SCOPE

The term medical product can describe things that vary in size, scope, complexity, importance, and
cost by several orders of magnitude. All of the material covered here is applicable over virtually all
of that range, but the relative importance of and effort spent in various elements will vary in the same
way. A stage that requires a year in the development of one product may be completed as part of a
single meeting on another. The reader is cautioned to exercise judgment in this regard. Judgment will
be found to play a major role throughout any product development effort.

1.3 QUALITIES OF SUCCESSFUL PRODUCT DESIGN

Before proceeding it may be useful to define the objectives of this section more specifically.
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Eppinger and Ulrich suggest that there are five aspects to the quality of a product design effort:
• Product quality
• Product cost
• Development cost
• Development time
• Enhanced development capability
Product quality in this context is the overall accumulation of desired characteristics—ease of
use, precision, attractiveness, and all of the other things that one finds attractive in artifacts. Cost is,
of course, the cost to manufacture. In general, the market determines a product’s selling price, while
the cost is determined by the design. There are differing opinions about where in the design process
cost becomes locked in—in the conception, the details, or the manufacturing start-up—and it no
doubt differs for various products, but it is always within the scope of the material discussed here.
The profitability of the project depends on the difference between the two, the gross margin. That
difference must cover the other expenses of the enterprise with something left over. In the medical
device business, those other expenses are much higher than in most sectors. Costs of selling, track-
ing, providing customer service, etc., are higher for medical devices than for other products of equiv-
alent function. The development cost of the product is another of those expenses that must be covered
by the margin. (It is also one that is higher in the medical device sector.) It represents an investment
and is apportioned over the life of the product. Development time is often tightly related to develop-
ment cost, as projects tend to have a spending rate. In addition, the investment in development cost
must be recovered in a timely way, which only begins when the product begins to sell. Furthermore,
it is generally accepted that the product will eventually be replaced by another in the market, and that
the “window” of opportunity opens when the product is introduced and begins to close when its
successor appears. The design team can widen the window by an earlier introduction.
The last of these qualities needs some explanation. The process used here results in good docu-
mentation of the design activities. This results in an opportunity for those engaged to re-evaluate the
work done and to learn from that effort. Coming out of a design effort with an organization better
equipped to undertake the next task is an important benefit of doing it well. Design of medical products
is always done in a rapidly changing milieu where the rate of learning is very important.

1.4 CONCURRENT ENGINEERING

Although a recently coined term, concurrent engineering embodies an approach that has been around
for a very long time. Simply stated, it asks that a design be developed from the outset by a team that