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Optimized transfer functions: Design of Experiments (DOE) is the backbone
of the process design and the redesign improvement. It represents the most
common approach to quantify the transfer functions between the set of
CTSs and/or requirements and the set of critical factors, the Xs, at different
levels of the design hierarchy. DOE can be conducted by hardware or
software (e.g., simulation). From the subset of a few vital X's, experiments
are designed to manipulate the inputs actively to determine their effect on
the outputs (Big Ys or small ys). This phase is characterized by a sequence
of experiments, each based on the results of the previous study. “Critical”
variables are identified during this process. Usually, a small number of Xs
accounts for most of the variation in the outputs.
The result of this phase is an optimized software entity with all functional require-
ments released at Six Sigma performance level. As the concept design is finalized,
there are still a lot of design parameters that can be adjusted and changed. With the
help of computer simulation and/or hardware testing, DOE modeling, robust design
methods, and response surface methodology, the optimal parameter settings will be
determined. Usually this parameter optimization phase will be followed by a toler-
ance optimization step. The objective is to provide a logical and an objective basis
for setting the requirements and process tolerances. If the design parameters are not
controllable, we may need to repeat stages 1-3 of software DFSS.
DFSS tools used in this phase:
Transfer function detailing (physical DOE, computer DOE, hypothesis testing,
etc.)
Process capability analysis
Design scorecard
Simulation tools
Mistake-proofing plan
Robustness assessment
Software DFSS Phase 4: Verify and Validate the Design
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This phase spans the following two stages: Verification (Stage 6) and Launch
Readiness (Stage 7).
Stage 6: Verification
Stage 6 Entrance Criteria
Closure of Tollgate 5: Approval of the gate keeper is obtained
Risk assessment
TG “6”—Stage 6 Exit Criteria
After the optimization is finished, we will move to the final verification and
validation activities, including testing. The key actions are:
The pilot tests are audited for conformance with design and operational doc-
umentation.
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See Chapter 19.
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