Page 178 - Six Sigma Demystified

Chapter 7 i m p r o v e S tag e 159

evaluating Process Failure Modes

Once the process flow is established, it can be evaluated for its failure modes.
Understanding process failure modes allows one to define mitigation strategies
to minimize the impact or occurrence of failures. These mitigation strategies
may result in new process steps, optimal process settings, or process control
strategies to prevent failure. In some cases, where failure cannot be prevented
economically, a strategy can be developed to minimize the occurrence of the
failure and contain the damage.
Cause- and- effect diagrams used in the analyze stage are again useful for
brainstorming the potential causes of failures. This brainstorming activity will
provide necessary input to process decision program charts and failure modes
and effects analysis (FMEA).
The process decision program chart, also known by its acronym PDPC, is a tool
for identifying problems that can occur in a project or process and developing
contingencies (either a solution or work- around) to deal with each problem.
The PDPC has the same general format as a tree diagram. For each process
i
step shown in the first level, potential problems ( “what- fs”) are identified in the
second level. Countermeasures provide the contingencies for each problem.
The intent of the analysis is to confront problems that otherwise might not have
been addressed. Forcing the team to anticipate problems before they occur helps
team members to uncover issues or solutions that otherwise would be ignored.
Additionally, this process allows team members to discuss points that they may
find troublesome without feeling like they are being unduly negative. Once the
potential problems are identified, the next step is to think of measures to counter-
act those problems. When more than one countermeasure is available, note each

of them, and prioritize the solutions using the methods discussed earlier.
For instance, suppose that the anticipated problem is resistance to change
among process personnel. The possible counteractive measures include an
incentive program to boost morale and an education program to inform work-
ers of the need for change. You then can weigh the costs and benefits of each
alternative to decide on your course of action. Of course, it is much easier to
make these decisions in the calm of the planning room than in the heat of the
project when you suddenly discover an unanticipated problem.
Failure modes and effects analysis (also known by its acronym FMEA or failure
modes, effects, and criticality analysis) is a more detailed approach to the prob-
lem. It is used to determine high- risk functions or product features based on
the impact of a failure and the likelihood that a failure could occur without