FMEA - Preventive vs Detection Control

[Jimmy123]

I have always a discussion when I have write a test into the detection or prevention control. Example I do a leakage test with different parameters. The intention is to prevent a weakness of my design. Why should I write this as a detection? Any definition what’s the characteristic of the measure?

 

[Miner]

Is this for a DFMEA or PFMEA? I am guessing you meant DFMEA.

It would be difficult for a leakage test to prevent a design weakness. By the time you get to the point of testing, the design is nearly finalized, so this would be detection. An example of a preventative design control would be a finite element analysis of a design concept. This would allow you to revise the concept before the first prototype was built thus preventing the design weakness.

 

[Jimmy123]

Is this for a DFMEA or PFMEA? I am guessing you meant DFMEA.

It would be difficult for a leakage test to prevent a design weakness. By the time you get to the point of testing, the design is nearly finalized, so this would be detection. An example of a preventative design control would be a finite element analysis of a design concept. This would allow you to revise the concept before the first prototype was built thus preventing the design weakness.

But, we discussed, if the leackage test is done the effidence of the design is proved, that means related to occurrence.

 

[Miner]

You still have not specified whether this is a DFMEA or PFMEA.

You are assuming that it passes the leakage test. What if it fails?

 

[Jimmy123]

You still have not specified whether this is a DFMEA or PFMEA.

You are assuming that it passes the leakage test. What if it fails?

Sorry, we create D-FMEA. If it fails, this is a sign that the design is not robust as we think, maybe increase the O evaluation.

 

[indubioush]

Is the leak caused by a component and the leak test takes place as part of receiving inspection?

 

[Cephissus]

If you make multiple leak tests by changing various dimensions each time, you are using the leak tests to define your components dimensions, it qualifies as such as a Prevention Action.

If you have already determined the dimensions of your components and which to see whether your design is robust by leak testing, then it is a detection action.

What do you think?

 

[John Predmore]

In a DFMEA, which is the failure analysis of a design process, a low Detection score indicates confidence that the Design activity is likely to uncover a design shortcoming (such as a tolerance stackup) which was otherwise overlooked in the design. If there is a potential failure of the design output, for example a seal not being robust under all conditions and the failure effect is severe, one way to improve the RPN score is greater validation activity. That could mean longer test runs, larger sample size, inner/outer array type DoE, HALT, intentionally building worst-case tolerance stack-up combinations, testing artificially aged parts. In one sense, you are preventing a failure which has not yet occurred, but through detection in the design engineering process.