Page 113 - Design for Six Sigma a Roadmap for Product Development

88 Chapter Three

hypotheses, depending on the way in which the fundamental
knowledge areas are treated. Fundamental knowledge that can’t be
tested, yet is generally accepted as truth, will be treated as axioms.
If the fundamental knowledge areas are being tested, they are
treated as hypotheses. Design axioms (Suh 1990) and TRIZ
(Altshuller 1988) hypotheses are examples of fundamental knowledge
in DFSS theory.
The major objective of DFSS is to “design it right the first time” to
avoid painful downstream experiences. The term “Six Sigma” in the
context of DFSS can be defined as the level at which design vulnera-
bilities are not effective or minimal. Generally, two major design vul-
nerabilities may affect the quality of a design entity:

■ Conceptual vulnerabilities that are established because of the viola-
tion of design axioms and principles.
■ Operational vulnerabilities due to the lack of robustness in the use
environment. Elimination or reduction of operational vulnerabilities
is the objective of quality initiative including Six Sigma.

The objective of the DFSS when adopted upfront is to “design it right
the first time” by anticipating the effect of both sources of design vul-
nerabilities. This requires that companies be provided by the analyti-
cal means to achieve this noble objective and sustain it. Many
deploying companies of the Six Sigma philosophy are devising their in-
house views of DFSS. It is the authors’ perception that most of the
thinking about DFSS in many companies who are leading the DFSS
deployment is geared toward different packaging of the DMAIC
methodology plus “voice of the customer” tools. Their proposed deploy-
ment of DFSS is concentrated around phasing DMAIC methods in the
development process boosted, however, with dosages of tool complexity
(e.g., multiple regression instead of simple linear regression). This track
does not guarantee the achievement of Six Sigma capability in the
design entity. Additionally, because of unavailability of data in the
early design phase, most of the current Six Sigma tools may be useless.
In this context, the proposed DFSS strategy in this book has the view
depicted in Fig. 3.15. Accordingly, the DFSS should be based on new
tools that should take into consideration the unique nature of the
design process itself.
On the hard side, in order to “design it right the first time,” the DFSS
theory presented in this book is designed to attack both types of design
vulnerabilities to have Six Sigma yield of the designed entity. This objec-
tive can be achieved not only by targeting the entity itself but also by
extending DFSS deployment to the developmental processes that produce