Quality in Design - Medical Device Design: Innovation from Concept to Market - page 148

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Environment: environment the device is in and the effect this has.

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Methods: how device is used and could be misused; instructions that are required.

There are several herringbone models: some with eight arms, some with more, and some with
less. It matters not. The main aim of Ishikawa is to get you to think about external factors and
how they affect the performance of your device. Once again you can then feed this back into
your FMEA to undertake a more detailed analysis.

7.6 D4X
We meet the D4X (Design for X) family of tools when we come to product realization
(that is doing the actual “dirty work” of design). However they are also very valuable in
design quality too. Let us, for example, examine Design for Assembly (D4A) . In the normal
context this is taken as designing the device so that it can be assembled quickly and easily
on the shop floor. This is fine for the automotive industry but useless for the medical devices
industry. How many of our devices are assembled just prior to use? I would suggest the
majority. Hence it is a quality issue, as poor D4A will have a detrimental effect on the
company's reputation.

Hence, even though the D4X tools are presented in another chapter you should also read them
in the context of design quality.

7.7 Six Sigma
I have mentioned Six Sigma (or 6 σ ) numerous times in this text. There is little doubt that
this is the section where it is introduced properly. Without doubt it is the product of the
end of the twentieth century ( Bicheno and Catherwood, 2005 ) and is the culmination of
disparate quality systems into a coherent strategy. It was first introduced and developed
by Motorola with the sole ambition of reducing failures to 6 σ , or 3.4 defects per million;
an increase of 100× the quality they had previously. The genius of 6 σ is in its simplicity;
it took all of the quality tools already developed and combined them into a new package.
Hence many of the tools used are already well known by designers and engineers. One
of the disadvantages of 6 σ is that it is heavily policed and to be a 6 σ practitioner you
must have studied an accredited course and achieved one of their belts (note the link with
a martial art!). But the benefit of the widespread adoption is that there is a plethora of
textbooks that contain all the information you need to do an adequate job. If you want your
company to be 6 σ through and through then I'm afraid there is no avenue but to undergo
the expensive training programs.