Process FMEA (Failure Modes Effects Analysis) Severity Rating and RPN

[tattva]

Pfmea

Hi everybody!

Just had A PSO from one of my customers to release a new product, during PFMEA he asked for corrective actions for activities with severity 9 or higher, Is this right? I mean do I have to do this?

I looked all over FMEA manual and gives no information if i should or not, hope someone can help me in this matter.

Thanks in advance!

 

[ben sortin]

Every good PMEA has a recommended action for all potential failure modes. A nine is a nine, so fix it in the design.

 

[M Greenaway]

Am I right in thinking that you cannot change the severity rating ?

Only reduce the occurrence, or improve the detection ??

 

[Sam]

Am I right in thinking that you cannot change the severity rating ?

Only reduce the occurrence, or improve the detection ??

You are correct.

 

[howste]

Like Ben implies, severity rankings can only be changed with a design change.

Tattva, If your customer requires it in their CSRs or contract, you have to have to do it. Unfortunately I've seen far too many suppliers "fudging" numbers to avoid customer requirements like that. Realistically, you should consider improvement to failure modes that have a severity that high, but blindly requiring it doesn't seem right. If your severity is 9 with occurrence 1 and detection 1, is it really necessary? Can you give us some idea of the RPN or occurrence/detection rankings for these?

 

[Bill Ryan - 2007]

My answer is "It depends". I'm not sure how your customer defines a "9" but the AIAG guidelines say it is a Safety item with warning. If you have a Detection level of 1 (Poke-Yoke), so you are guaranteed to catch the failure and not ship it to your customer, and your management can "live with" whatever the Occurence value reflects, your customer should be fine. There is nothing wrong with a note in the Recommended Actions that simply states "No action to be taken at this time" to show that it was reviewed.

Sam is correct - you cannot reduce Severity on a PFMEA.

Every good PMEA has a recommended action for all potential failure modes.

I don't buy that!!!

Bill

 

[tattva]

Actually RPN is 18 Occ=1 and Det=2, the problem is that this is for physical test activities and he argued this was a very important issue

 

[Rob Nix]

There are times when the severity is high but the likely of occurence is sooooo rare, or ease of detection soooo obvious that nothing further is to be done.

There are no rules attached to specific RPN numbers, nor detection or occurence numbers, that require action. This is a thought process, where each issue is considered on its own merit. The numbers just serve as guidelines.

I've worked with companies that "pareto-ize" the RPNs, and simply work on the top 10 or 15. Others say anything above 6 for each category requires action. I've tried to help all of them see that the value of the FMEA is in the exercise, not the precise numbers derived.

 

[Howard Atkins]

There is a second aspect of the 9 rating and perhaps this is how your customer looks at it

This ranking results when a potential Failure Mode results in a final customer and/or a manufacturing/assembly plant defect. The final customer should always be considered first. If both occur, use the higher of the two severities.​

(Manufacturing/ Assembly effect)​

Or may endanger operator (machine or assembly) with warning. 9​

​

​

​

​

From the Ford FMEA training manual
​

Path/Step 1 of the Working Model is completed by considering
​

appropriate Recommended Actions to:
​

a. Eliminate the Failure Mode
​

b. Mitigate the effect
​

To reduce Severity, consider this action:​

​

Change the design (e.g., geometry, material) if related to a product characteristic or change the process if operator safety is involved or if it relates to a process characteristic.​

To accomplish this:​

·​

Eliminate Failure Mode(s) or change its effect on the product performance.
​

If you believe that it is a design issue then you should return this to your customer for his action.
If it is your process then you should deal with it.

 

[Marc]

A nine is a nine, so fix it in the design.

Yup!