FMEA - Reduce Occurance of a Failure (or its cause) by Design Change

Hi everybody,

1- anybody knows if one can use FMEA ranking tables (for S,O,D) directly in an FMEA session, or one has to customize these tables for a specific product? If yes, does anyone has a customized ranking system?

2- FMEA reference Manual suggests that to reduce Occurance of a failure (or its cause) one has to undertake a design change. On the other hand, in the example given for DFMEA it seems with with increasing test they have managed to reduce the occurance ranking? Don't these two statements seem contradictory?

[Marc]

Originally posted by KAVOSH:

1- anybody knows if one can use FMEA ranking tables (for S,O,D) directly in an FMEA session, or one has to customize these tables for a specific product? If yes, does anyone has a customized ranking system?

Typically each product has at least some custimization. I don't have an example off hand.

2- FMEA reference Manual suggests that to reduce Occurance of a failure (or its cause) one has to undertake a design change. On the other hand, in the example given for DFMEA it seems with increasing test they have managed to reduce the occurance ranking? Don't these two statements seem contradictory?

What pages in the FMEA manual are you looking at?

[Qualiman]

Originally posted by KAVOSH:
Hi everybody,


2- FMEA reference Manual suggests that to reduce Occurance of a failure (or its cause) one has to undertake a design change. On the other hand, in the example given for DFMEA it seems with with increasing test they have managed to reduce the occurance ranking? Don't these two statements seem contradictory?

You can reduce occurrence by attacking the potential CAUSES of failure and detection by making changes on your process/design CONTROLS, but severity will only be reduced making changes in your design in order to reduce the EFFECT of the failure

Qualiman

Originally posted by Marc Smith:
What pages in the FMEA manual are you looking at?

Dear Marc,

I was refering to FMEA manual, design FMEA, the example given there. In the example they seem to have decreased Occurance by increasing design controls (which is meant to decrease Detection). On the other hand in the main text of the manual they suggest that only through design change you can reduce Occurance !

Originally posted by Qualiman:
You can reduce occurrence by attacking the potential CAUSES of failure and detection by making changes on your process/design CONTROLS, but severity will only be reduced making changes in your design in order to reduce the EFFECT of the failure

Qualiman

Dear Qualiman,

That is exactly my point! In the DFMEA example (FMEA manual) they have only included more Lab Testing (more Control) and it seems as a result Occurance has decreased !? This means they haven't attacked the cause, doesn't it?

[Dawn]

Kosha,
A test will only detect an occurence; not reduce it. What type of test was it in the book? (My book is at work). You can use the tables in the book. To customize your own tables would be ok; but not necessary; as the tables are pretty much a "shall" on what numbers to give.
Hope this helps a little.

Originally posted by Dawn:
Kosha,
A test will only detect an occurence; not reduce it. What type of test was it in the book? (My book is at work). You can use the tables in the book. To customize your own tables would be ok; but not necessary; as the tables are pretty much a "shall" on what numbers to give.
Hope this helps a little.

Thanks Dawn.
The test in the FMEA reference manual was a corrosion test on car door.
Thanks for the adivce.