Severity Occurrence Detection Ranking Scale - 1 to 10 vs. 1 to 5

K

kurisuoriari

#1
Hello another FMEA Topic from me.

A couple of years ago we reviewed our Severity Occurence Detection Ranking.

A broad difference exsisted in using scales of 1 to 10.
As a improvement the scales were refined to 1 to 5.

Thus I have a Max RPN of 125.
This has worked fine and provides good repeatability of classification for different users and team members.

However a recent customer auditor discussed my ranking and has documented a requirement to review the ranking. His point is that the range does not allow the correct priority since a higher range would seperate items of greater importance.

However I demonstrated that because I took all RPN of the same value with the same action priority and had no RPN's above 12 on any process in our plant my process was working effectively. This could also be justified by the quality of product supplied to this customer meeting target requirements.

Yet I fear that this auditor wants me to install a 1 to 10 ranking and if this is not carried out on the corrective action report he will not close this issue and improve my supplier ranking.

Any Thoughts ?

Cheers

Chris
 
Elsmar Forum Sponsor

Jim Wynne

Staff member
Admin
#2
This isn't actually a FMEA question, it's a customer-requirements question. The question is: how can I deal with customer requirements that don't make sense? First, if you've done your best to diplomatically convince your customer contact that the requirement doesn't make sense, you have two choices. You can just accept the nonsensical requirement and move on, or you can go over the guy's head. There's an excellent chance, though, that his boss will have no idea what you're talking about and find it much easier just to back his own guy. Even if the boss does rule in your favor, there's an excellent chance it will come back to haunt you, and at the worst possible time.
In short, this is a decision you have to make for yourself, because you should have a much better feel for the particulars of this situation than anyone here does. We don't know the customer, or the customer's representative, or how easy or difficult it would be to make a change and move on.
 
D

dokes

#3
Interesting situation. I wonder if there is any evidence of the reliability of a 10 point scale versus a 5 point scale. Frankly there is not a big difference between a 9 or 10 in a 10 point scale, both of which a 5 would cover on a 5 point scale.

If they've not done so, I'd ask the customer representative to create a short example of an FMEA using both 5 and 10 point scales, to demonstrate what s/he believes would occur and what the impact would be. I would then determine the degree to which this would likely occur with your product/application, and whether or not there is any evidence it has occurred.

I would bet this is just a usual "this is the way I've always seen/done it in the past" ... imposing additional costs on a supplier. Just make sure your next bid to them includes this additional cost.
 
R

Rob Nix

#4
As JSW05 (aka A.E. Newman) says, if your customer requires it, then that's the way it is (unless you can convince them otherwise). That is why a good contract review process is so vital! If discussed and documented then, there would be nothing the auditor could fault you on now.

But, on another vein,
kuri... said:
A broad difference exsisted in using scales of 1 to 10.
As a improvement the scales were refined to 1 to 5.
Therein lies the problem with FMEAs. As I've stated in other threads, the FMEA exercise is an excellent tool. But the overemphasis on ranking numbers and risk priority numbers is counterproductive. The fact is, for each line on the FMEA, you choose either to do something to improve it or not. Period.

The skills and cross-functionality of the team members are the important part. They identify the risks and decide which risks are too high to leave alone. You make a list of those things, prioritize them, and make assignments. All of the gyrations surrounding this number or that number shifts the focus away from the whole purpose of the exercise. IMHO anyway.
 

Jim Wynne

Staff member
Admin
#5
Rob Nix said:
As JSW05 (aka A.E. Newman) says, if your customer requires it, then that's the way it is (unless you can convince them otherwise). That is why a good contract review process is so vital! If discussed and documented then, there would be nothing the auditor could fault you on now.

But, on another vein,

Therein lies the problem with FMEAs. As I've stated in other threads, the FMEA exercise is an excellent tool. But the overemphasis on ranking numbers and risk priority numbers is counterproductive. The fact is, for each line on the FMEA, you choose either to do something to improve it or not. Period.

The skills and cross-functionality of the team members are the important part. They identify the risks and decide which risks are too high to leave alone. You make a list of those things, prioritize them, and make assignments. All of the gyrations surrounding this number or that number shifts the focus away from the whole purpose of the exercise. IMHO anyway.
I agree. The numbers are an unnecessary distraction, and lead to dangerous strategies such as "trigger" RPNs--if RPN is >X, actions are required. The trigger strategy came about as a result of auditors questioning FMEA documents that show no "right-hand activity" and auditees needing to come up with an appropriate explanation for it.
 
B

Bill Ryan - 2007

#6
I haven't vented in a while..... so here goes :mad:

This is yet another example of someone trying to impose his/her "ideal" onto a supplier that, apparently, has a methodology that works for them. The fact that it DOES work for you is of no consequence. It's the "Do it my way or there's the highway" syndrome. I have to go along with JSW (something new :rolleyes: ) in that you need to weigh the pros and cons of the battles you take on (with anyone). I also agree with Dokes in that this is how the AIAG manual presents the FMEA methodology and your customer probably doesn't understand what FMEA is all about, other than through the AIAG manual (I do, however, highly doubt the customer rep would go through the excersise you cited).

End of rant (I think):thanx:

In practice - do you really do much different if something has a severity of 9 or 10? If the difference between 9 & 10 is with or without warning, it is still a "Safety" feature that must be thoroughly dissected and kept "under control". If a Detection is ranked 9 or 10 you are probably going to go through the same excersize to lower the ranking (depending.....) because you, basically, can't "catch" the nonconformance.

What's the difference between 7 and 8? Or 5 & 6 (even with the Occurrence and Detection ratings)? I realize that customers have come out with their own, grandiose, rating tables but I still refuse to sit with a team and argue whether something should be rated as this number or maybe one higher. Maybe, just maybe, the 1-5 scale would actually help stop that kind of activity as you mentioned with the "good repeatability of classification" comment.

One of the issues could be that your customer doesn't know how to handle a "bogey" number that his organization has set (but let's not rehash that pain in the a** topic).

If I were in your position (again):
All in all - as JSW mentioned, there are occasions where it is best to "bite the bullet" and cave in. If that's the route you decide on, I wouldn't change anything you do internally. I would merely change the ratings for that customer on the document he sees and if he "knows" that you have just fooled with the numbers, tell him that's what his demands necessitated because you aren't about to disrupt a system that works well for you. That doesn't sound very "ethical" but most organizations I've seen don't handle different systems for the same process very well - and it IS your company, not theirs.

(Wow, am I wound up this morning ;) )
 

Jim Wynne

Staff member
Admin
#7
I have to go along with JSW (something new :rolleyes: )
One of the great things about the Cove is that it presents varying informed opinions to people with questions. Disagreement is a good thing, so long as it's not just contrarianism (did I just make up a word?).

Bill Ryan said:
That doesn't sound very "ethical" but most organizations I've seen don't handle different systems for the same process very well - and it IS your company, not theirs.
I don't think it's necessarily unethical when you give the customer what he asks for:D .
 

Tim Folkerts

Super Moderator
#8
Since you roughly cut in half the assigned scores (5 on a 1-5 scale = 10 on a 1-10 scale), how about simply doubling the numbers for this particular customer when you report the results. Since there are 3 scores, then you would multiple the final score by 8. So 125 --> 1000, or 1 --> 8. This will tend to overestimate the score slightly, but
1) it will be in the right ballpark (which is all you can really hope for)
2) it will be in terms the customer will appreciate.

I suppose the customer could argue that a 3x3x3 = 27 on your scale could be anthing from 5x5x5 = 125 up to 6x6x6 = 216 on a 10 point scale. Still, in the grand scheme of FMEA's that's not such a huge range. You are just trying to get a rough estimate of overall importance, after all.


Tim F
 
D

D.Scott

#9
I agree with the others that you have to pick your battles when dealing with customers. I also agree that the calculation of RPNs usually doesn't make much sense. Once again, the further down the line you are, the less sense they seem to make. Now for the disagreement.

I don't buy that a reduction of the scale from 1 to 10 is an improvement. By dropping from an RPN of 1000 to 125 would look great on paper but what did you actually do? The "nice looking" 125 is still the same "worst case" it would be at 1000 so what was accomplished?

The idea of a FMEA is to identify where the problems might be, not to grade the quality supplied to the customer. The FMEA is simply a tool to look at potential problems that might appear anywhere in processing.

There is a good chance that whatever you are making/processing is only a component of a larger "end" product. If that's the case, the information supplied by you for your portion of the process should be as compatible and understandable as possible with and to the others involved in the realization of the product.

For this reason alone, it is understandable that the scale of 1 to 10 was established and published as a guide for determining RPNs. When viewed as a piece of the "big" FEMA, your changes in formatting or calculations could be causing a problem up the line that you may not be thinking about. For the sake of uniformity and customer satisfaction, I would revert to the 1 to 10 scale. My honest opinion is if you insist on pushing it, you will find you are flogging a dead horse. This is not one of the "battles-to-pick".

Dave
 
J

Jconlake

#10
A Little Humble Opinion

The customer who insists on their ranking on a FMEA w/o a specific way it will improve the operation probably:

Would not recognize their own part if they saw it in production.

Probably can not read a blueprint.

Probably has no clue how to actually improve anything.

Probably can be intimidated into silence if you just drop the name of a higher ranking customer at their company who insisted on a scale of 1 to 5.

Ask them why you should stop at 10. After all, would not a scale of 1 to 100 offer you even more differentiation? How about a scale as wide as the number of dimensions on the part? You can even use heavier paper on the pages with the highest RPN's. You can scale the font according to the Severity. How about using Japanese symbols on the items with the lowest RPN?

Don't forget to point out that if you are forced to use a scale with a top end of 2 digits, you will have to increase your price to compensate. That is the reason why GM internally spells employee with only 1 "e", to save us all a few dollars on cars.

Better yet, give the customer blank pages and tell them it was prepared with invisible ink to protect their valuable info. It can only be read by holding the paper over an open flame.
 
Last edited by a moderator:
Thread starter Similar threads Forum Replies Date
D How to fill a Process FMEA - Three columns - Severity, occurrence and Detection FMEA and Control Plans 16
R DFMEA Severity 9-10 with Occurrence 3 and Detection 3 - Actions FMEA and Control Plans 3
K 4th Edition AIAG FMEA Occurrence, Severity and Detection Criteria for Plastics FMEA and Control Plans 1
L FMEA Occurrence, Severity and Detection Criteria FMEA and Control Plans 3
Y Severity, Occurrence and Detection FMEA Ranking Tables - Guidelines? FMEA and Control Plans 8
V Emphasizing Severity more than Occurrence and Detection vs. Overall RPN FMEA and Control Plans 20
E FMEA Severity, Occurrence, and Detection Rating - I am in need of some examples FMEA and Control Plans 19
R PFMEA - RPN - Severity, Occurrence and Detection - Which one does not change? FMEA and Control Plans 67
E Risk Management selection Probability of Occurrence and Severity ISO 14971 - Medical Device Risk Management 24
D Severity or Occurrence? Performing an FMEA on Motorcycle Operation FMEA and Control Plans 9
I Ford FMEA requirements for Severity and Occurrence Rankings Customer and Company Specific Requirements 1
R DFMEA/PFMEA mitigation of high severity (9-10) in low volume products IATF 16949 - Automotive Quality Systems Standard 1
silentmonkey How to measure severity if my product is designed for emergency use and failure would result in death? ISO 14971 - Medical Device Risk Management 9
J On PFMEA for danger labels - Label always should be assigned severity 10 ? FMEA and Control Plans 3
S The Severity of a Medical Device Hazard - Risk Analysis Clarification ISO 14971 - Medical Device Risk Management 6
MrTetris Informational Risk Register - Same hazardous situation, different severity of harms ISO 14971 - Medical Device Risk Management 7
A PFMEA severity score different applications FMEA and Control Plans 11
X Customer Service FMEA - Specifically Customer Care / Severity Rankings Service Industry Specific Topics 3
S What should the FMEA Severity for SC & CC Characteristics be? FMEA and Control Plans 4
N AIAG 4th ed. FMEA Manual "Fit" Changed to "Appearance" - Fit severity? FMEA and Control Plans 2
G Severity in Process FMEA for Rework Process FMEA and Control Plans 1
O PFMEA - Reducing Severity (S) Ranking - Manufacturing Process Design Changes FMEA and Control Plans 4
S FMEA's - Severity and Classification of Print Characteristics FMEA and Control Plans 1
N Risk Severity Estimation for Medical Devices as per ISO 14971 ISO 14971 - Medical Device Risk Management 12
C Determining PFMEA Severity for Armored Parts FMEA and Control Plans 5
C FMEA DOGMA about Severity - Am I right or Wrong? FMEA and Control Plans 2
F Risk = Likelihood * Severity - Can we mitigate the Severity? Occupational Health & Safety Management Standards 44
M Severity Reduction in a Design FMEA (DFMEA) FMEA and Control Plans 25
S Severity of 9 or 10 should be identified as Special characteristic? FMEA and Control Plans 10
G Internal vs. External PFMEA Severity Rankings FMEA and Control Plans 12
R Risks which must be Distinctly Identified - Harm, Hazard, Severity ISO 14971 - Medical Device Risk Management 7
C Severity of Effect on Process (Manufacturing/Assembly Effect) Scrap or Reworking FMEA and Control Plans 3
W Severity Rating CORRECTIVE ACTIONS - Opinions Wanted Please Nonconformance and Corrective Action 15
H DFMEA Severity Ranking of Non-Compliance to EMC Standards FMEA and Control Plans 2
P Chemical Purity Testing - FMEA Severity Scale FMEA and Control Plans 2
T FMEA Severity 9 &10 - Example of "with warning?" FMEA and Control Plans 6
E Harms Severity Scoring - Combination of Hazards ISO 14971 - Medical Device Risk Management 4
B The Distribution that represents the Severity of Nonconformances Nonconformance and Corrective Action 2
A AIAG Design FMEA Severity Rankings - Noncompliance Government Regulation? FMEA and Control Plans 9
G FMEA Severity Ranking for an Automotive Audio System FMEA and Control Plans 9
Chennaiite FMEA Severity Rating for Potential Manufacturing Effect mentioned in the FMEA manual FMEA and Control Plans 9
kedarg6500 FMEA Severity Scale - Higher for Failure at Customer's or End-Customer's place? FMEA and Control Plans 19
M FMEA Severity Ratings for Health Care Information System FMEA and Control Plans 10
C Does the PFMEA Severity have to match the DFMEA Severity? FMEA and Control Plans 3
P Measuring Severity of Construction Nonconformance Report Nonconformance and Corrective Action 3
L Standard for process control level depending on gravity (severity)? FMEA and Control Plans 7
I Defining a Severity Level of a non-conformance Nonconformance and Corrective Action 13
L FMEA - Should a severity of 9 or 10 be always followed by recommended actions? FMEA and Control Plans 2
J Severity of Finding for "Past Due Gage" found on the shop floor General Measurement Device and Calibration Topics 40
S FMEA Severity of 9 or 10 - Shower does not operate FMEA and Control Plans 13

Similar threads

Top Bottom