Page 35 - Biomedical Engineering and Design Handbook Volume 2, Applications

14 MEDICAL DEVICE DESIGN

In addition to the economic and technical reasons that support modularity, it can assist in a
medical product gaining acceptance. If the product can be viewed by the clinician as having a number
of modules that are familiar, along with some new functionality, it may be easier to introduce than a
system that is viewed as an entirely new approach. Most medical professionals are somewhat
conservative and like to be on ground that is at least somewhat familiar. This could be a consideration
in choice of architecture and even in the details of the deconstruction process.
In many designs, the layout of the system is obvious. Similar products have been broken out the
same way to everyone’s satisfaction, and no other arrangement seems possible. On the other hand, it
is good practice to ask if this is indeed the optimum architecture for the given product, and explore
the advantages and disadvantages of altering the architecture.

1.13 DETAIL DESIGN

The detail design phase is where the individual components of the system are fully defined. Again, the
issues here vary greatly across the product spectrum, but primarily the issue is function against the vari-
ous penalties of weight, space, cost, etc. None of these are unique to the medical device area, but the
costs tend to be higher, the penalty for error much higher, and therefore the need for care very intense.
It is good practice to use commercially available components as much as possible as long as they
do not compromise the design functionality in any way. Each and every part that is unique to the
product will require careful specification, manufacturing study, shape, and manufacturing documen-
tation, manufacturing qualification, etc. It is difficult to estimate the cost of adding a part to a medical
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product production system, but Galsworthy quotes a source from 1994 stating that the average in
the commercial world is no less than $4000. The medical product equivalent must be an order of
magnitude larger.
As the parts are designed, consideration must be given to not only the manufacturing process to
be used, but also the method of testing and verifying functionality. Some foresight at the detail level
can provide “hooks” that enable the initial testing of the part, the system, and even the ongoing quality
assurance testing that good manufacturing practice mandates. Providing an electrical contact point
or flat on which to locate a displacement probe can make what would otherwise be a project into a
routine measurement.

1.14 DESIGN FOR MANUFACTURE

The need for design for manufacture goes without saying, since one of the primary measures of suc-
cess in product development is cost to manufacture. There is a strong belief among developers that
the cost to manufacture a product is largely determined at the concept-selection stage, but there is a
great deal of evidence that indicates details of design based on selection of manufacturing methods
are the real determining factors. The major stumbling block here is that so many manufacturing
processes are volume sensitive. The design of parts for the same physical function and annual vol-
umes of 1000, 100,000, and 10 million would call for three totally different manufacturing processes.
In detailing the part, it is important to know the production targets. Things can be designed to tran-
sition from low volume to high volume as the product gains market, but it needs careful planning and
good information. This is one of the places that the team’s skills in marketing, design, and manu-
facture can pay large dividends.

1.15 ROLLOUT

Bringing the product out of the trial phase and into manufacturing and the marketplace is the last
responsibility of the team. The initial product planning should have defined target sales volumes, and