Page 187 - Design for Six Sigma a Roadmap for Product Development

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design and process failure modes and sources of potential variation in
manufacturing, assembly, delivery, and services processes should be
determined. FMEA considerations include the variations in customer
usage; potential causes of deterioration over useful design life; and
potential process issues such as missed tags or steps, package and
shipping concerns, and service misdiagnosis. The team should modify
the design and processes to prevent “wrong things” from happening
and involve the development of strategies to deal with different situ-
ations, the redesign of processes to reduce variation, and errorproof-
ing (poka-yoke) of designs and processes. Efforts to anticipate failure
modes and sources of variation are iterative. This action continues as
the team strives to further improve the product design and processes.
We suggest using the FMEA concept to analyze systems and subsys-
tems in the early concept and design stages. The focus is on potential
failure modes associated with the functions of a system caused by the
design. Design FMEA (DFMEA) is used to analyze designs before they
are released to production. In the DFSS algorithm, a DFMEA should
always be completed well in advance of a prototype build. The input to
DFMEA is the array of FRs. The outputs are (1) list of actions to pre-
vent causes or to detect failure modes and (2) history of actions taken
and future activity.
Process FMEA (PFMEA) is used to analyze manufacturing,
assembly, or any other processes. The focus is on process inputs.
Software FMEA documents and addresses failure modes associated
with software functions.

5.9.1 The Use of FMEA and its links in the
DFSS algorithm (DFSS algorithm step 8)
Failure management using the FMEA is an iterative process that
promotes system and concurrent engineering thinking. The most promi-
nent failures are related to functional requirements. Since components,
subsystems, and systems have their own FRs, the FMEA development
should be paced with structure detailing.
FMEA can be easily linked to other tools in the DFSS algorithm, such
as the P-diagram (process diagram; see Fig. 5.15), fishbone diagram,
physical and process structures, transfer functions, process mappings,
and DOE, both classical and robust design. Among these tools, the P-
diagram deserves more attention as the newly introduced tool that was
skipped in previous chapters. The P-diagram is a robust design tool used
to summarize and capture inputs and outputs of a scoped design or
process entity. It distinguishes between factors on which the DFSS team
has control, the DPs at different hierarchal levels, and factors that they
can’t control or wish not to control because of technology or cost
inhibitors, the “noise” factors. Noise factors cause design failures and do