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DFSS Transfer Function and Scorecards 199

6. Maintenance. This is achieved by controlling all significant inde-
pendent variables, after optimization, either in house or outside.
7. Disposal. The design transfer functions are disposed or reach enti-
tlement in delivering high-level FRs either when new customer
attributes that can’t be satisfied with the current design emerged,
or when the mean or controlled variance of the FRs are no longer
acceptable by the customer. This stage is usually followed by the
evolution of new transfer functions to satisfy the emerged needs.
8. Evolution of a new transfer function. Per TRIZ, an evolution usu-
ally follows certain basic patterns of development. Evolutionary
trends of the performance level of the functional requirements
(FRs) of a certain design can be plotted over time and have been
found to evolve in a manner that resembles an S curve (Fig. 6.9).
The following are the possible sources of “detailed” transfer functions:
1. Direct documented knowledge such as equations derived from
laws of physics (e.g., force mass
acceleration or voltage current
resistance, profit price cost, interest formulas)
2. Derived transfer functions based on the direct documented
knowledge as related to the project scope. For example, a DFSS project
scope is to design a building elevator controller formed from many
electric circuits. The team can rely on electric circuit analysis, which is
based on direct documented knowledge of transfer functions such as

FR

New Invention Infant Stage

Invention Mature Stage

Invention Intermediate Stage
Invention Intermediate Stage
Invention Infant Stage

Time
Figure 6.9 The S curve of FR evolution.