What You Need to Know About Failure Mode and Effects Analysis (FMEA)
Every product or process has modes of failure. The effects
represent the impact of the failures. An FMEA is a tool to:
- Identify the relative risks designed into a product or
- Initiate action to reduce those risks with the highest
- Track the results of the action plan in terms of risk
FMEAs help us focus on and understand the impact of potential
process or product risks. A systematic methodology is used to
rate the risks relative to each other. An RPN or Risk Priority
Number is calculated for each failure mode and its resulting
effect(s). The RPN is a function of three factors: The
Severity of the effect, the frequency of Occurrence of the cause of
the failure, and the ability to detect (or prevent) the failure or effect.
- RPN = Severity rating X Occurrence rating X Detection rating
- The RPN can range from a low of 1 to a high of 1,000
Once the RPNs are determined, you need to develop an Action Plan
to reduce the risks of failure modes of unacceptably high RPNs.
Next, use the FMEA as the basis for developing a Control Plan.
Control Plans are a summary of defect prevention and reactive
FMEA Checklists and Forms
Many of these forms can be downloaded as Excel Spreadsheets or Word
Tips to Make FMEAs More Effective
Customize the rating scales
While industry guidelines suggest customizing generic ranking
scales, they do not require it. However, by taking the time to add
organization-specific examples of applications of the ranking
definitions, FMEA teams will have an easier time applying the
scales. The use of meaningful, relevant examples saves teams time
and improves consistency of rankings from team to team.
Use the same (custom) ranking scales throughout the organization
Once a custom set of ranking Scales are developed, use them for
every FMEA study conducted in the organization. By using the same
scales, the RPN for every failure mode and effect can be compared on
a relative level and the highest potential risks for the
organization can identified.
Add a Control Plan right to the FMEA Worksheet
Control Plans ensure a system is in place to control the risks of
the same failure modes identified in the FMEA. While Control Plans
can be developed independently of FMEAs, it is time- and
cost-effective to link Control Plans directly to FMEAs. The Control
Plan describes how each potential failure mode will be controlled
and how it should be reacted to if it (the failure mode) does occur.
To add a control plan component to an FMEA, add “columns” to the
FMEA Worksheet for the control factors, the specifications and
tolerances, the measurement system, sample size, sample frequency,
the control method, and the reaction plan.
Use a team approach
A team will be able to generate a more comprehensive list of
potential failures than any one individual could do. A team approach
will lead to a richer and more accurate analysis of the risks
associated with a process or design.