FMEA is an easy-to-use yet powerful pro-active engineering quality
method that helps you to identify and offset weak points in the early
conception phase of products and processes. The structured approach
makes it easy to use and, even for non-specialists, a valuable tool.
The benefits obtained encompass by large, the investments in time and
resources to execute the analysis.
There are several types of FMEAs, some are used more often than others.
FMEAs should always be done whenever failures would mean potential harm
or injury to the user of the end item being designed. The types of FMEA
are:
FMEA can be employed before new services, processes, or products are
purchased or implemented, to identify potential failure modes and so
steps can be taken to avoid errors before they occur.
| Step 1 |
Select a process (function, product) to evaluate
with FMEA |
| Step 2 |
Recruit a multidisciplinary team |
| |
Be sure to involve everyone that may be involved at
any point in the process |
| Step 3 |
Have the team meet to discuss and list all
the steps in the process |
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Number every step in the process and be as specific
as possible. |
| Step 4 |
Have the team list all the failure modes and
causes |
| |
A failure mode is defined as the manner in which
a component, subsystem, system, process, etc. could potentially
fail to meet the design intent.
List everything that could go wrong including minor and rare
problems.
Identify all possible causes for each failure mode.
A failure mode in one component can serve as the cause of a failure
mode in another component. Each failure should be listed in technical
terms. Failure modes should be listed for the function of each
component or process step. At this point, the failure mode should
be identified whether or not the failure is likely to occur. Looking
at similar products or processes and the failures that have been
documented for them is an excellent starting point. |
| Step 5 |
For each failure mode, determine the potential
effect |
| |
Describe the effects of those failure modes. For
each failure mode identified, the engineer should determine what
the ultimate effect will be. A failure effect is defined as the
result of a failure mode on the function of the product/process
as perceived by the customer. They should be described in terms
of what the customer might see or experience, should the identified
failure mode occur. Keep in mind the internal as well as the external
customers. (See
sample chart) |
| |
Likelihood of occurrence: |
| |
1: |
It is highly unlikely OR
It has never happened here before |
| |
5: |
It is very likely OR
It happens here frequently |
| |
Likelihood of Detection: |
| |
1: |
It very likely |
| |
5: |
It is highly unlikely |
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Severity: |
| |
1: |
no harm OR
no damage |
| |
5: |
permanent harm OR
total damage |
| Step 6 |
Determine which failures to work on |
| |
Calculate the Risk Priority Numbers (RPNs)
- Multiply the three (3) scores obtained for “likelihood
of occurrence”, “likelihood of detection”,
and “severity”.
- Identify the failure modes with the top 10 RPNs.
|
| Step 7 |
Use Risk Potential Numbers (RPNs) to plan
improvement efforts |
| |
Failure modes with high RPNs are usually the most
important parts of the process to concentrate on improvement efforts. |
| |
1. |
If failure mode is likely to occur, |
| |
|
a. Evaluate causes to determine if they can be eliminated:
- What safeguards are in place?
- Do the safeguards work?
- What would have to go wrong for this failure to occur?
- Why wouldn’t the failure be caught and corrected before
it occurs or reach the customers?
|
| |
|
b. Consider using force function
c. Add a verification step
d. Modify other processes that contribute to the causes |
| |
2. |
Design and implement improvement strategies to prevent failures. |
| |
|
a. Eliminate the chances of errors
b. Make it easier for people to do the right thing
c. Identify errors quickly and take appropriate actions |
| |
3. |
Monitor actions taken through documentation. |
