Page 180 - Design for Six Sigma a Roadmap for Product Development

Design for Six Sigma Project Algorithm 153

Concepts
…
FRs

FR 1
s –2 +3 –1
FR 2
s –2 –2 –2
:
s –1 +1 +3
:
s +3 +3
–1
s
FR m

Total (–)
Total (+)

Figure 5.11 Pugh generation-selection matrix.

■ Select the best concept with the maximum number of plus signs and
minimum number of minus signs.

5.7 Finalize the Physical Structure of the
Selected Concept (DFSS Algorithm Step 6)

The first step in design detailing is to develop the physical structure
that determines the opportunity to capture the “maximum potential for
customer satisfaction” defined in step 2. The purpose of the physical
structural definition is to establish an enabler to subsequent concept
and detail design efforts to realize this maximum potential. The
axiomatic design method provides the zigzagging process as the means
to define physical and process structures. The structure is captured
mathematically using mapping matrices with matrices belonging to the
same hierarchical level clustered together. Hierarchy is built by the
decomposing design into a number of simpler functional design matri-
ces that collectively meet the high-level functional requirements
obtained from phase 2 QFD. The array of FRs should be checked for
independence, that is, that they are different and distinct. For example,
speed and torque are independent functional requirements, although
they are constrained by physics. This requirement is needed because it
forms a minimum array to design, for that will have the potential to
satisfy design requirements. Extra functional requirements may not be
demanded by the customer and will result in either overdesign or poor