Page 57 - Six Sigma for electronics design and manufacturing

The Nature of Six Sigma and Its Connectivity to Other Quality Tools
In summary, the FMEA process is comprised of the following steps:
1. FMEA preparation
Select FMEA process team and complete a process map. Identify
all process steps.
List process outputs to satisfy internal and external customers.
List process inputs for each process step and rank them.
Develop a relationship matrix, relating product to process steps.
2. FMEA process 27
List ways process inputs can vary and identify failure modes.
List other causes and sources of variability.
Assign severity, occurrence, and detection rating for each cause.
Calculate risk priority number (RPN) for each failure.
3. FMEA improvements
Determine recommended actions with time needed to reduce
RPN.
Forecast risk reduction and take appropriate action to reduce
failure risk.
Recalculate RPN and put controls in place to ensure that failure
is completely eliminated from the system or process. An exam-
ple of an FMEA chart is given in Figure 1.8.
1.11.2.2 FMEA definitions
Failure mode: A statement of fact describing what would happen
when a system, a part, or a process has potentially failed to meet
the designer specification intent or performance requirements.
The cause might be a design flaw or a change in the product that
prevents it from functioning properly.
Effect: A description of what the end user will experience or notice.
The users might be line operators, the next department to re-
ceive the parts, or the customers.
Cause: The reason why a failure occurred.
Severity(SEV): How significant is the impact of the effects to the
customers (internal or external)?
Occurrence (OCC): How likely is the cause of the effect to occur?
Detection (DET): How likely will the current system detect the
cause of the failure mode?
Risk priority number (RPN): A numerical calculation of the relative
risk of a particular failure mode, obtained by multiplying the
severity, occurrence and detection numbers of each failure listed
in the FMEA chart.