Page 423 - Design for Six Sigma a Roadmap for Product Development

Failure Mode–Effect Analysis 389

concept FMEA to analyze systems and subsystems in the early concept
and design stages. This focuses on potential failure modes associated
with the functions of a system caused by the design. The concept
FMEA helps the DFSS team review targets for the FRs, select opti-
mum physical structure with minimum vulnerabilities, identify pre-
liminary testing requirements, and determine if hardware system
redundancy is required for reliability target settings. Design FMEA
(DFMEA) is used to analyze designs before they are released to pro-
duction. In the DFSS algorithm, a DFMEA should always be com-
pleted well in advance of a prototype build. The input to DFMEA is
the array of functional requirements. The outputs are (1) list of
actions to prevent causes or to detect failure modes and (2) history
of actions taken and future activity. The DFMEA helps the DFSS
team in

1. Estimating the effects on all customer segments
2. Assessing and selecting design alternatives
3. Developing an efficient validation phase within the DFSS algorithm
4. Inputting the needed information for Design for X (DFMA, DFS,
DFR, DFE, etc.; see Chap. 10)
5. Prioritizing the list of corrective actions using strategies such as
mitigation, transferring, ignoring, or preventing the failure modes
6. Identifying the potential special design parameters (DPs) in terms
of failure
7. Documenting the findings for future reference

Process FMEA (PFMEA) is used to analyze manufacturing, assem-
bly, or any other processes such as those identified as transactional
DFSS projects. The focus is on process inputs. Software FMEA docu-
ments and addresses failure modes associated with software functions.
The PFMEA is a valuable tool available to the concurrent DFSS team
to help them in

1. Identifying potential manufacturing/assembly or production process
causes in order to place controls on either increasing detection,
reducing occurrence, or both
2. Prioritizing the list of corrective actions using strategies such as
mitigation, transferring, ignoring, or preventing the failure modes
3. Documenting the results of their processes
4. Identifying the special potential process variables (PVs), from a fail-
ure standpoint, which need special controls