Page 370 - Design for Six Sigma a Roadmap for Product Development

340 Chapter Nine

comparing these “lower-level design rules” with TRIZ tools is useful
in order to understand these two methodologies. Only three theo-
rems are selected because we do not think other theorems in AD can
be linked with TRIZ. Mann (1999) gives the general comparisons of
AD and TRIZ at the level of domain, mapping, hierarchies, and
axioms.

Axiomatic design TRIZ
Corollary 1: Decoupling of coupled design. Contradiction concept in TRIZ is similar
Decouple or separate parts or aspects of a to the functional coupling in AD.
solution if FRs are coupled or become Overcoming contradiction in TRIZ means
interdependent in the proposed design. the removal of functional coupling in AD.
This corollary states that functional There are two types of contradiction:
independence must be ensured by technological contradiction and physical
decoupling if a proposed design couples contradiction. A technological
the functional requirements. Functional contradiction is derived from a physical
decoupling may be achieved without contradiction. So, certain changes of the
physical separation. However, in many physical structure of a technological
cases, such physical decomposition may system guided by the “contradiction table”
be the best way of solving the coupling and the 40 “inventive principles” or
problem (Suh 1990). “separation principles” are often required
to remove contradiction.
Corollary 2: Minimization of FRs. Ideal final result (IFR) philosophy
Minimize the number of functional corresponds to Corollary 2 in AD. IFR
requirements and constraints. This states that a system is a “fee” for
corollary states that as the number of realization of the required function and
functional requirements and constraints IFR will be realized if the system does not
increases, the system becomes more exist but the required function is
complex and thus the information content performed. IFR helps an engineer focus
is increased. This corollary recommends on concepts that minimize requirements
that the designer strive for maximum in substance, energy, and complexity of
simplicity in overall design or the utmost engineering product and process.
simplicity in physical and functional
characteristics.
Corollary 3: Integration of physical parts. Evolution pattern 5: Increased complexity
Integrate design features into a single followed by simplification. This pattern
physical process, device or system when states that technological systems tend to
FRs can be independently satisfied in the develop first toward increased complexity
proposed solution. This corollary 3 states (i.e., increased quantity and quality of
that the number of physical components system functions) and then toward
should be reduced through integration of simplification (where the same or better
parts without coupling functional performance is provided by a less complex
requirements. However, mere physical system). The term mo-bi-poly indicates
integration is not desirable if it results in that monofunction products evolve into
an increase of information content or in a bifunction or polyfunction products
coupling of functional requirements. through integration of physical
embodiments.