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alan1jones
Has anybody got any experience of this?
Re: FMEAs using P-diagrams
Have a look at this thread: P-diagram in FMEA preparation - What does the "P" stand for in "P-diagram"?.
Have a look at this thread: P-diagram in FMEA preparation - What does the "P" stand for in "P-diagram"?.
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alan1jones
Re: FMEAs using P-diagrams
Had already found this thread. I think i'm getting a bit hung up generation of 'control factors' and then the how the information is transcribed into an FMEA.
Thanks Jim,
Had already found this thread. I think i'm getting a bit hung up generation of 'control factors' and then the how the information is transcribed into an FMEA.
M
Michael Walmsley
Re: FMEAs using P-diagrams
Hope this helps.
Hope this helps.
Last edited by a moderator:
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alan1jones
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alan1jones
Re: FMEAs using P-diagrams
It does seem to be a speedier and more logical way to pick up failure modes and causes, instead of moving down an FMEA line by line. I'm just not sure how to translate the p-diagram into an FMEA.
M
Michael Walmsley
Re: FMEAs using P-diagrams
The value of any analytical process lies in the fact that it either causes you to think or not.
Functional blocks provide you with the overview of the big picture.
It answers the questions of :
What is the environment?
What are the interfaces?
How do they generically interface?
What are the regulatory requirements?
Who owns what?
Still there is a lot of room for needed improvement.
The P-Diagram attacks a subset of the elements in the Functional Block causing you to break these interfaces down and analyze them at a lower level.
For a particular interface ("System" in the pictures , Item in the FMEA),you may have a group of functions that are to be performed .These ideal functions are prompted by an input signal. In an FMEA the Input signal defines "Function". The "Ideal Function Output" is the function broken down into its constituent parts.
The anti-Function is the failure mode.
The "Error States" in the P-Diagram can either allude to the Failure Effect in the FMEA or causes/mechanisms.
The "Control Factors and Noise Factors" further define specific items to look at in defining failure causes/mechanisms.
See attached brief example (does not include everything provided on earlier attachment).
The benefit for me of using the P-Diagram,lies in the fact that it causes me to think before I act in filling out an FMEA. I use it specifically to help me develop System and Component DFMEA's. It could probably be used on PFMEA's,but I have not had an opportunity yet.
The FMEA has had a bad rep over the years because some people approach it and blindly fill it out ,offtimes leaving out important info. Because of this,we have product recalls or loss of business.
To me the P-Diagram in conjunction with the Design Functional Block (or Process Map) forces further discipline into the FMEA process.
The value of any analytical process lies in the fact that it either causes you to think or not.
Functional blocks provide you with the overview of the big picture.
It answers the questions of :
What is the environment?
What are the interfaces?
How do they generically interface?
What are the regulatory requirements?
Who owns what?
Still there is a lot of room for needed improvement.
The P-Diagram attacks a subset of the elements in the Functional Block causing you to break these interfaces down and analyze them at a lower level.
For a particular interface ("System" in the pictures , Item in the FMEA),you may have a group of functions that are to be performed .These ideal functions are prompted by an input signal. In an FMEA the Input signal defines "Function". The "Ideal Function Output" is the function broken down into its constituent parts.
The anti-Function is the failure mode.
The "Error States" in the P-Diagram can either allude to the Failure Effect in the FMEA or causes/mechanisms.
The "Control Factors and Noise Factors" further define specific items to look at in defining failure causes/mechanisms.
See attached brief example (does not include everything provided on earlier attachment).
The benefit for me of using the P-Diagram,lies in the fact that it causes me to think before I act in filling out an FMEA. I use it specifically to help me develop System and Component DFMEA's. It could probably be used on PFMEA's,but I have not had an opportunity yet.
The FMEA has had a bad rep over the years because some people approach it and blindly fill it out ,offtimes leaving out important info. Because of this,we have product recalls or loss of business.
To me the P-Diagram in conjunction with the Design Functional Block (or Process Map) forces further discipline into the FMEA process.
Re: FMEAs using P-diagrams
I can't help but feel that there's some serious overcomplication going on here, and perhaps some confusion over what "FMEA" means. In the description above, the P-diagram is part of the FMEA process, not something that precedes it. FMEA is not filling out a form; the form is only a record of what took place. It's really very simple, I think. If you start out with a rational separation of process operations (commonly manifested in a process flow diagram), then all you have to do is:
I can't help but feel that there's some serious overcomplication going on here, and perhaps some confusion over what "FMEA" means. In the description above, the P-diagram is part of the FMEA process, not something that precedes it. FMEA is not filling out a form; the form is only a record of what took place. It's really very simple, I think. If you start out with a rational separation of process operations (commonly manifested in a process flow diagram), then all you have to do is:
- Gather the people who have significant knowledge of the operation and the larger process;
- Get them to make suggestions as to anything that might possible go wrong;
- Make a list of those things, and then eliminate those that are obviously too unlikely to be concerned about;
- Rank the remaining potential problems in order of severity (where the term has been previously explicitly defined) and then in order of likelihood of occurrence, and then in order of the likelihood that a given failure will be detected before further value is added;
- Appraise each item, in the order ranked, to determine whether preventive measures may be taken and/or if detection methods can be improved;
- Do something;
- Make a record of all of the above.
M
Michael Walmsley
Re: FMEAs using P-diagrams
Jim,
I can't fault your logic w/r to PFMEA.
As I have said, I have not used it there.
For S/DFMEA,it is an invaluable tool that is used to precede these processes.
I usually fill out the P-Diagram after the Functional block with the engineers.
We then use it as an input to the S/DFMEA.
W/r to filling out the "form",this has been a common problem that I have had to overcome with many engineers. This is their "view". Not mine.
Jim,
I can't fault your logic w/r to PFMEA.
As I have said, I have not used it there.
For S/DFMEA,it is an invaluable tool that is used to precede these processes.
I usually fill out the P-Diagram after the Functional block with the engineers.
We then use it as an input to the S/DFMEA.
W/r to filling out the "form",this has been a common problem that I have had to overcome with many engineers. This is their "view". Not mine.
