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Internal vs. External PFMEA Severity Rankings

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GoKats78

#1
We are in the middle of revisiting our PFMEAs in an effort to make them relevant (after 5 years of struggling to get this project started).

We have come up against an interesting dilemma. The severity ranking guidelines we are using come from Honda and have separate criteria for "Effect on Product (Customer Effect)" and "Effect on Process (Manufacturing/Assembly Effect)"

What happens here is we end up with situations where the internal severity is higher (7 or 8) than the external severity. (usually based on the section of the criteria that states "A portion of the production run may have to be scrapped.") but the effect to the customer is much lower (5 -6: Loss of secondary function - vehicle operable, but comfort/convenience functions inoperable).

We have an internal rule that if the severity of a process is 7 or 8 that limits who (full-time vs. temporary) can run the process. Any changes to that rule will be vetoed by our customer as was driven by them years ago...

We are almost to the point of developing a PFMEA with 2 separate Severity Rankings (and therefore, 2 different RPN's) based on internal vs external issues.

How have others dealt with the issue?
 
G

guruprasadb

#2
HI,

We have also implemented the severity ranking by considering the potential effect of failure ---in

Operator Safety:
Next Operation:
Vehicle / Customer:
Govt Regulations:

severity will be ranked cosideration each effect in above category

in some processes we had three RPN 's

I am attaching the sample format for your reference
 

Attachments

Chennaiite

Never-say-die
Trusted
#3
We have an internal rule that if the severity of a process is 7 or 8 that limits who (full-time vs. temporary) can run the process. Any changes to that rule will be vetoed by our customer as was driven by them years ago...

We are almost to the point of developing a PFMEA with 2 separate Severity Rankings (and therefore, 2 different RPN's) based on internal vs external issues.

How have others dealt with the issue?
I don't understand your need to develop FMEA with two different Severity rating. Generally, it's the Severity of the most serious effect that influences RPN or risk assessment. Probably, I miss something here? May be you think of projecting lower Severity in your Customer copy in order to avoid his intervention?
 
G

GoKats78

#4
I don't understand your need to develop FMEA with two different Severity rating. Generally, it's the Severity of the most serious effect that influences RPN or risk assessment. Probably, I miss something here? May be you think of projecting lower Severity in your Customer copy in order to avoid his intervention?
No..it has to do with whom can perform the process (full time vs temporary associate)
 
#5
I am not altogether convinced that anything good will come from fiddling too much with proven concepts like FMEA. The basic RPN setup looks pretty solid to me, and I frown a bit when each customer (in this case Honda) persists in coming up with their own homegrown setups. If a supplier has a large number of customers, all of whom require the use of their particular guidelines this will cause nothing but unnecessary confusion and red tape.

In short: Keep it simple, and do try to apply lean concepts to the lean process itself. Otherwise it will become a burden (muda) in its own right.

/Claes
 
G

GoKats78

#6
I am not altogether convinced that anything good will come from fiddling too much with proven concepts like FMEA. The basic RPN setup looks pretty solid to me, and I frown a bit when each customer (in this case Honda) persists in coming up with their own homegrown setups. If a supplier has a large number of customers, all of whom require the use of their particular guidelines this will cause nothing but unnecessary confusion and red tape.



/Claes
I agree...but Honda is over 90% of our business...
 
G

GoKats78

#8
Here is the line in the guidelines causing us all the headaches:
A portion of the production run may have to be scrapped. Deviation from the primary process including decreased line speed or added manpower.
This puts a "7" severity on the process. Almost any process you could have to scrap something if something goes wrong!

What we are new considering is looking more at the second part (Deviation from the primary process including decreased line speed or added manpower.) for internal processes and considering the whole guideline for our customer
 

Chennaiite

Never-say-die
Trusted
#9
Here is the line in the guidelines causing us all the headaches:

This puts a "7" severity on the process. Almost any process you could have to scrap something if something goes wrong!

What we are new considering is looking more at the second part (Deviation from the primary process including decreased line speed or added manpower.) for internal processes and considering the whole guideline for our customer
Generally speaking, this understanding seems to make sense for me. What really may also influence the severity rating is the nature of your product, process and the failure mode.

I am saying this because with reference to AIAG Manual, the whole idea of line speed, 100% scrap, additional manpower, etc only go behind exploring what if the effect of a failure mode is detected before reaching the end user. Its true that when it comes to detection of effect, the detection at customer end takes front seat rather than the one before despatch. Hence it makes sense that 100% or portion scrap is more serious at Customer end than at site.
Having said that, we may have to be careful with handling process step such as Heat treatment where the process happens in batches and hence scrap within site may also happen in batches. This may even have disastrous effect on the machining process, where as can go undetected at the customer end assembly. Thats why I believe one should also consider higher level effects such as Major/Significant/Moderate disruption before going any further.
 

Helmut Jilling

Auditor / Consultant
#10
Remember, when evaluating Severity, you evaluate the failure impact on the OE customer and on the end user of the vehicle, and take the higher of the 2 numbers.
 
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