Design FMEA ( DFMEA )
A Design FMEA ( DFMEA or Design Failure Mode and Effects Analysis ) is performed during the design stage of a product to determine how it might fail, how likely such a failure would be (Occurrence), how serious it would be (Severity) and whether such a failure would be detected during the development programme (Detection).
There are several levels of a Design FMEA (DFMEA).
A System FMEA
This is performed on a whole system or subsystem and can be started before the detail design of all the parts has been undertaken. In fact it should be started as early as possible.
A Design FMEA
This is done on smaller assemblies, down to part level if necessary. This is usually done a bit later in the design and development process, but it should not be left too late.
How to do a Design FMEA
The process is similar to a brainstorm and should involve a multi-disciplinary team of ideally 4-8 people. The results are recorded on a special form (often an Excel Spreadsheet). The Severity, Occurrence and Detection are each scored from 1-10, and then these scores are combined into a Risk Priority Number (RPN), to give an overall ranking. Those with the highest RPN are identified for action to reduce the RPN. This can often result in a re-design, which is why doing an FMEA should not be left too late. Also Significant & Critical Characteristics are identified, which are those for which a Process FMEA should be performed.
An example is shown below.
Note: The detection score should quantify the likelihood that the Design Verification Plan (DVP) detects the problem during the engineering programme. Therefore an initial DVP should exist and be known prior to performing the FMEA.
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