Page 184 - Design for Six Sigma a Roadmap for Product Development

Design for Six Sigma Project Algorithm 157

In a decoupled design case, a design matrix of lower/upper triangle
DPs is adjusted in some sequence conveyed by the matrix. Uncoupled
and decoupled design entities possess conceptual robustness, where
the DPs can be changed to affect intended requirements only without
readjustment of any unintended functional requirements. Definitely, a
coupled design results when the matrix has the number of require-
ments greater than the number of DPs. The coupled design may be
uncoupled or decoupled by “smartly” adding extra DPs to the struc-
ture. Uncoupling or decoupling is an activity that is paced with struc-
ture detailing and can be dealt with using axiomatic design theorems
and corollaries. Uncoupled and decoupled designs have higher poten-
tials to achieve Six Sigma capability in all FRs than do coupled
designs. Design for Six Sigma in the conceptual sense is defined as
having an overall uncoupled or decoupled design by conducting the
process mapping and physical mapping concurrently by the team.

5.7.3 Simplify design using axiom 2
(DFSS algorithm step 6)
After maintaining independence per axiom 1, the DFSS team should
select the design with the least information content. The less informa-
tion specified to manufacture or produce the design, the less complex
it is; hence, information measures are measures of complexity. In gen-
eral, “complexity” is defined as a quality of designed entities.
Complexity in design has many facets, including the lack of trans-
parency of the transfer functions between inputs and outputs in the
physical structure, the relative difficulty of employed physical and
transactional processes, and the relatively large number of assemblies,
processes, and components involved (Phal and Beitz 1988). In Chap. 8,
we explore different techniques to simplify the design. For now, suffice
it to say that the number, variance, and correlation relationships of the
design elements are components of design complexity.

5.8 Initiate Design Scorecards and Transfer
Function Development (DFSS Algorithm Step 7)

The functional requirements in the physical structure can be further
detailed by design scorecards and transfer functions, two unique con-
cepts of the DFSS algorithm (Chap. 6). The transfer function is the
means for dialing customer satisfaction and can be initially identified
via the different design mappings. A transfer function is a relation-
ship, preferably mathematical, in the concerned mapping linking con-
trollable and uncontrollable factors. Transfer functions can be derived,
empirically obtained from a DOE, or regressed using historical data.