On page 43, the standard states that when the severity of the RPN is high, special attention should be given to it. What does everyone consider high? We have been using 100.

I have found that different suppliers have various "limits" for RPN's but I think the bigger picture would be to have some type of prioritized reduction plan for your highest RPN's.

In a previous life we even had a helpful SQA that gave us RPN numbers of our competitors (no names involved) to benchmark against.

I would like to hear from other forum members if they have any specific supplier limits they could share.

ASD...

------------------
Al Dyer
Mngt. Rep.
ullysses3@excite.com

"What does everyone consider high"
IMO 1000 or higher. Special attention when severity is 7 or higher.

From the FMEA manual;
"The risk oriority number is the product of severity (S), Occurrence (O), and detection (D). RPN = (S) x(OD) x (D)
This value should be used to rank order the concerns in the process (e.g., in Pareto fashion)
The RPN will be between "1" and "1,000". For higher RPN,s (higher than 1000) the team must undertake efforts to reduce this calculated risk through corrective action(s). In general practice, regardless of the resultant RPN( S x O x D ), special attention should be given when severity (page 35) is high (7,8,9,10)"
Note: expressions in parenthesis is my input.

[This message has been edited by Sam (edited 17 January 2001).]

I would discourage an arbitrarily established value. Failing to deal with a value below '100' might prove to be determental.

On the other hand, unwisely dispensing resources to countermeasure a low rating could prove equally bad.

Keep in mind that the FMEA is a LIVING DOCUMENT. This means it must be revisited from time to time. As such, you might find that an RPN for an item that was low because of a false expectation proves to be high. The reverse is also true. Still, as the process or system changes, the RPN could toggle back and forth.

So when do you react? Well, what is a manageable risk? Keep in mind that the organization for the most part is the AUTHORITY on the process or design. You make the decision as to what is a high or low risk (please pay attention to regulatory requirement, ie Essential Requirements which govern your actions). Being the authority on the product/process, the experts, and having knowledge of your manageable resources, you pick your own battles.

Another not so scientific method, but perhaps better than arbitrarily established RPNs, is to use the 80/20 principle. Use Pareto analysis to establish your priorities and address the "vital few" as your resources permit. Use Corrective/Preventive Actions. As you periodically do your review the FMEA, update your RPNS,reprioritize, and repeat the process.

Just another opinion.

Regards,

Kevin

At a minimum, we require the following...

1. Any RPN >= 100 must have an action plan to reduce.

2. If no RPN's are over 100, the top 3 RPN's must be considered. Why considered and not an action plan?...because if my top RPN is 20, I will probably get more value out of my engineers elsewhere.

3. Any severity of 9 or 10 must be evaluated. Again, the resultant RPN could be low if occurrence and detectability are 1, but because a 9 or 10 can affect safe vehicle operation or impact a govt. regulation, they deserve special attention.

You have all posed some interesting points of view with respect to the action or lack of action relating to a particular level of RPN. As I see it, the FMEA provides a micro view of your product or system in a prioritized fashion similiar to the Pareto chart which we are all familiar with. The major difference is that the FMEA provides actions and responsibilities and a feedback on the effect of these actions via the re-calculated RPN. Each element on the FMEA should be looked at as an oppurtunity for improvement, obviously with the higher RPN's providing the greatest bang for a buck. Rather than only focusing on RPN's reaching a level you should look at the entire system. Perhaps reducing a number of smaller RPN's may be more timely or economical than placing all of your resources on a single element. Additionally you should not discount the effect of lowering one RPN on other elements in the system. You may see some surprising relationships.

I’m agreeing with Al. In the spirit of continuous improvement, there needs to be some kind of prioritized reduction plan (a.k.a… the pareto chart).

I have facilitated a number of FMEA meetings. I have noticed if there is a arbitrary cut off value, all of the RPN’s magically and conveniently fall below that value. Now, it make take a bit of time and group justification to accomplish this, but by the end of the day they have convinced themselves of it.

If the RPN’s are on a pareto chart, I have found the group to achieve more realistic RPN’s and make the FMEA process more productive.

Anybody else experience this?


[This message has been edited by AJLenarz (edited 15 February 2001).]

[This message has been edited by AJLenarz (edited 15 February 2001).]

AJ,

Also agree and have been through it in depth.

Once a limit is set, it seems to be the mind set that human nature will direct you to set your "goals" below the acceptable limit.

Although goals need to be set, once continuous improvement is in place those goals have to be reset downward to continue the improvement process.

I think that internal goals, such as "PPM" must be set lower than any customer expectation.

I believe and have read/heard the mantra "Zero Defects".

Work this entire process into the actual cost of making a good product and we can all see that doing it right in the first place is a good premis, but that finding the faults in the process will lead to real, quantifiable results.

MHO

ASD...

FMEA's should not be used own their own. In my experience as an ex-Ford Quality engineer and now a senior engineer at a T-1, the use of FMEA's should be part of a process to make your product as robust to external noises as possible and also to incease the reliability of your product.

The Ford system of :

1. Quality History Analysis (FMA),
2. 'P' Diagram,
3. DFMEA (a. Block Diagram, b. Function Trees, c. DFMEA),
4. DVP,
5. PFMEA,
6. Control Plan

helps supplier and OEM engineers to look at what went wrong in the past and try to fix it for the future. An FMEA must consist of a cross-functional team and also include design, quality and manufacturing representatives.

FMEA's should not be looked at in isolation, but as part of a larger relibility and robustness (systems engineering) program.

I agree that the prioritized reduction plan is a must. And to set limits prior to the actual composition might be a mistake. The prioritization issue inevitably comes down to resources.
I also agree with Paul that the FMEa needs to be incorportade with other quality functions.
My 2 cents...

Hi all,

My opinion is that the RPN indication doesnot make sure that your process is safe-guarded against potential failure modes with the controls that you identify. There is an inherent methodology called Process review that can be practiced for the same. For eg., consider the following option:
S=5*0=7* D=5 = 175. We come to the conclusion that an action has to be taken.
But consider the following:
S=9 * O=5 * D=1
This will give an RPN of 45, but when the problem occurs, it will have a higher impact ont he customer. Hence the analysis tool has to be changed. What we are discussing will not work if you are targetting improvement.

Regards,
Arun Kumar

Hi guys,
I agree with Arun. Process review works!!!

Regards,
Ron Smith
Mgmt Rep.
Axles Inc.

Just a note: RonSmith is unregistered. I don't know exactly what the occasion is, but today Ron has left 7 messages each of which has been a confirmation of omnex. I wouldn't question this particularly, but with no registration it seems like a lot of love for omnex. I do hope this is not SPAM.

Arun, I feel that the FMEA manual provides all the guidance necessary to identify and analyse potential problems.

Ron, I have tried many software programs; the only one that gets my vote is MS excel.
We tend to make things to difficult by jumping from new fad to new fad and the one thing I don't need is some overated software package making my life more difficult.

RPNis an indication of how the safe the process is against the potential failure modes. However to have a perfect FMEA the following needs to be considered.
01. Potential Failure causes shall be identified taking into consideration Man, Material, Macheines, Methods & Environment.
02. Process Controls need to be identified from the following:
a.Controls that can Prevent the Failure Mode.
b.Controls that the Prevent the Cause of the Failure Mode.
c. Controls that can detect the Failure Mode.
d. Controls that can detect the Potential Cause of the Failure Mode.

If a FMEA is prepared taking into consideration the above the resulting RPN will have a close link with the Process and the Failure Modes.

Considering your example 2 even thought the RPN is only 45, Still action is required since the Severity is 9 which is very high which can affect the safety of the user & can be against the govt. regulations.

[This message has been edited by Marc Smith (edited 18 April 2001).]

If the severity is 9, occurrence is 1, and detection is 1, would you need to act on the situation.

I can't see why, severity is supposed to be determined by the customer and hypothetically out of your control. (internal or external customer doesn't matter)

As a supplier I would worry more about occurrence & detection than severity and RPN. O & D are within my control. This is not to say that RPN is discounted, if your O & D are high the actions would be commensurate with the severity level.

MHO

ASD...

On the Severity issue - if it is high - could you not suggest a design change to lessen its impact?

Only a thought.......

Originally posted by Paul Alexander:
On the Severity issue - if it is high - could you not suggest a design change to lessen its impact?

Only a thought.......

You sure could, it always helps to improve youself and help the customer!

ASD...

I would suggest that there is NO way to lower a severity rating with a design change.

For example, suppose the design in question is for a parachute. The severity of a failure to open would have to be a 10. How do you lower that severity?? A secondary parachute? That doesn't really lessen the severity, though. It just shifts it to the "n'th" redundant chute.

The fact of the matter is that severity of failure is not a function of the design. However, controlling the OCCURENCE and DETECTION RPN's is definitely facilitated by design alternatives, ie. design a chute with a 99.9999% successful deployment rating, and throw in a couple of redundant back-up chutes with equal success ratings, and your occurrence is extremely low.

But if the chutes don't open......

The severity rating cannot change. At least, I don't understand how.

What am I missing?

Originally posted by Help Me:

I would suggest that there is NO way to lower a severity rating with a design change.Are we talking process FMEA or Design FMEA?

Parachute: Design Intent is to reduce descent speed to survivable rate. The slower, the better.

Device failure mode: Chute does not open.
Device failure effect: Probable death.
Design change: Add small extra parachute so if main chute fails, the small chute can be deployed.

New failure effect: Probable broken leg bones.

********************************

Example of 'severity of failure' change as a result of a design change.

[This message has been edited by Marc Smith (edited 17 April 2001).]

My point is that then the small chute design has to be addressed. And the severity of the second chute failing to deploy is every bit as severe as a failure of the main chute to deploy.

If you get to the point where this chute is required and it, too, doesn't deploy, how have you reduced the overall severity? I don't think you have.

Sure, you have reduced the severity of the main chute not deploying (Assuming that the secondary chute deploys). If anything, the addition of the second chute has reduced the occurrence of the catastrophic failure (my earlier contention). But, the same severity exists no matter how many redundant chutes fail. Though, the occurrence will hopefully improve (eventually, one of the dang chutes will probably deploy).

I guess I am still missing something.

I'll keep thinking about it if you will.

I design a facial razor. It is rather crude and has no guard of any type (a razor blade on an old tooth brush). I can cut myself pretty good with this thing. Heck, I might be able to cut my jugular vein and die. Severity: 10

Now I like living. I like my customers to live to, so I design a safety razor. Pretty slick, but I can still cut myself. At present, my design will cut, but it would take great effort to kill myself. Severity: 9

This is a pretty extreme example, but with some time, we could all come up with things in our lives/work that if the design is changed, will result in a lower severity rating.

Regards,

Kevin

->My point is that then the small chute design has to be
->addressed. And the severity of the second chute failing to
->deploy is every bit as severe as a failure of the main
->chute to deploy.

Assuming a design FMEA, the DFMEA is about a product. A parachute. In the 'old days' it was nothing more than a half a bag with strings. As the design evolved different things happened. But the point is you take possible failures (e.g.: chute does not deploy) and rate them. Yes - if the main chute doesn't deploy and the small chute doesn't deploy you're still up s__t creek. But the probably of both failing is small compared to only 1 not deploying.

And, we're rating each failure mode individually. If you decide you want to assess what will happen if multiple failures occurr simultaneously you're going to be getting into a more complicated analysis.

->If you get to the point where this chute is required and
->it, too, doesn't deploy, how have you reduced the overall
->severity? I don't think you have.

The second chute is like adding a safety to a gun. It's not specifically required (or wasn't long ago). It's an enhancement of the gun design.

You should stop thinking about each possible individual failure mode as a catastrophic failure which causes the whole device (the product as a whole) to fail. This can happen but not always.

Just some thoughts.

Just to add,

Severity applies to Effect and there can be multiple Modes which have their own Severity which can be internal or external customers.

If need be for internal Severity, we can, and should define our own evaluation and ranking criteria.

Back to real life, Severity is defined by the customer and can be influenced by our suggestions to improve their processes. We all realize that during a PFMEA we have to "assume" that the DFMEA is viable.

MHO and waiting for more responses!

ASD...

I still hold that all you are really doing by adding safety chutes is favorably affecting the occurrence, therefore the overall RPN.

It is quite possible that the designer/manufacturer of the safety chute is not the same party that is designing/manufacturing the safety chute (remember, the chute example is hypothetical).

Since this forum is heavily automotive, I will try to use an automotive example:

The function of the wheels on the car are to provide directional stability. If a wheel falls off because the one and only lug nut included in the design falls off, the result is loss of vehicle control, possible injury/death.

Through analysis it is determined that three lug nuts are sufficient to retain the wheel in any real world situation. Being a very safety concious engineer (btw, I might want to drive one of these things) I decide that if three is sufficient, I will add three more to my design. This is kind of like replacing the razor blade on a stick into a safety razor (whchh, btw doesn't eliminate the potential for cutting the jugular. It just reduces the occurrence to nil).

Now I have 6 lug nuts in my design.

DOES THIS REDUCE THE SEVERITY OF THE FAILURE MODE: LOSING A WHEEL? Absolutely not. If the wheel falls off, I still have the potential of injury/death. Yes, this is another catastrophic event. But, by definition, that is what a severity 9-10 is.

Now, is the 6 lug wheel going to fall off? Very unlikely. But that doesn't change the severity the failure effect should it happen.

Isn't that what a design FMEA does? Take into consideration the:
Severity X Occurrence X Detection = RPN

From a design standpoint I have to appreciate a high severity. That high severity makes me pay particular attention to occurrence and detection factors.

The essence of a Design FMEA is, as it should be, to "What if" the design to death.

You contiinue to equate this to a catestrophic failure of the entire product. FMEAs look at one potential failure at a time. Just because you can cite one failure for which the severity may not change does not mean the severity of all possible failure modes are not changable. If you design in 6 lugs because 3 are deemed to be the least necessary to ensure against catestrophic failure (a common practice is to over-design) and your potential failure mode is lug nut or stud failure, it's severity rating will indeed be lowered from what the severity would be if you only had 1 lug nut and the nut or stud failed. If 1 lug nut or stud fails and there are 6 total, the severity of the failure of a lugnut or stud is next to nothing. Technically your FMEA could include line items (potential failure modes) for each - 1 lug fails, 2 lugs fail, 3 lugs fail, etc., but that is a bit much. If more than 3 lugs fail it is probably in response to an accident, hitting a high curb or other significant event.

You also have to look at the wording of your DFMEA. If the potential failure mode is lug nut failure, the potential effect will probably not be that the whole wheel will fall off if one fails (if you have 6 lug nuts). If you have only 1 lug nut then the potential effect of the failure mode would undoubtedly be that the wheel will fall off. So - by changing the design you have also changed the potential effect(s) of the failure.

So - with 1 lug nut the potential effect of the failure of a lug / stud is very serious. With a re-design to include 6 lug nuts total, the potential effect of a lug / stud failure isn't very significant. If you now take it to the extreme and say "...I want to address the issue of all studs failing simultaneously..." you have to put that in as a line item in and of its self as a potential failure mode.

Part of the mis-conception here may be from the fact that in a process FMEA the ONLY way to reduce severity is through a design change. This is typically true of Design FMEAs as well.

Another possible source of confusion here is that it is NOT necessarily true that every severity rating CAN be reduced. For SOME failure modes there is very little you can do to reduce severity of the potential effects. If your DFMEA line item for a Potential Failure Mode reads 'Failure of all lugs / studs simultaneously ' there is not much you can do to address severity.

Then again, with all the new electronics coming into play, this, too, may be reduced in the future (if it is not already) by recognition of the loss of traction, car body position, etc. So - you may, through a design change where a computer helps maintain control, in fact reduce the severity of all lugs / studs failing at the same time. The reduction in severity may be small, but it is there. It may be that loosing a tire in and of its self, for any reason, is not so much a problem because the computer helps maintain lateral stability.

BTW - I have had tires fall off of a car I was driving twice. Once with while pulling a loaded horse trailer a rear drive wheel of my van fell off (someone stole 3 of 5 lugs off each wheel the night before but I didn;t notice them missing) and once a front tire on a car I had (it had mags and like with the van someone decided they wanted my lugnuts late at night). Neither time did I loose control nor did I really feel I had lost control. Luckily I was on an expressway both times (and I won't begin to get into the flats I've had in my life).

To go to the extreme, you could put in a DFMEA a line item for a Potential Failure Mode of all lugs / studs on all wheels simultaneously failing with the Potential Effect being all wheels fall off of the car at the same time.

Bottom line is you miss the step where your design change (1 nut to 6) changes the effect of the failure.

With only 1 nut, the effect of the failure of 1 nut is the wheel falls off. With 6 nuts, the effect of the failure of 1 nut is not very severe at all. To addess the failure of all 6 simultaneously a new Potential Failure Mode line item has to be added.

BTW - You might want to take a read through http://Elsmar.com/FMEA/

Wellll, Mark and others,

The point I have been trying to make (unsuccessfully) is that the severity of the POTENTIAL effect of a failure cannot be reduced with a design change to that system in question. The anecdotal evidence of maintaining control of one vehicle after losing a wheel is, indeed, good news! Though, a less skilled driver, in different conditions, may not have been so lucky. But, maybe I made a mistake by choosing a bad HYPOTHETICAL (I wish I could make that word boldface and about 14 font sizes larger). So, I will refrain from trying to use any aditional hypotheticals.
I also agree that the switch to 6 lugnuts would drive new line items. One of which would have to be all 6 lugnuts failing simultaneously. High severity/extremely low occurrence (where have I heard this before?) Likewise, for the secondary, tertiary, nth chute. Severity for the main chute not deploying reduces because the high severity ranking trickles down to the nth chute. Though, eventually, you would run out of altitude before you run out of chutes, I suppose(HYYYYYYPOTHHHHETTTTTTTTTTICALLLLLLLLL).
The bottom line is that our ISO team where I work have picked up on the verbage in the FMEA manual that says that severity rankings can only be reduced by design changes. Therefore, in their minds, any severity ranking of 9-10 is not acceptable and must be reduced by way of design changes.

It is encouraging that you have stated that not all severity rankings can be reduced through design change. Unfortunately, they do not share your interpretation. In their minds, if any severity rankings can be addressed (Lowered) with a design change, then, all severity rankings can.

I know I am going to tick you all off again. But, I still think in the design changes you have suggested in your responses to my hypothetical cases only serve to shift the high severity rankings to another component/system.

I am going to quit posting on this subject as I cannot seem to make my point clear.

You're not 'ticking off' anyone.

On 17 April 2001 you said:

-> I would suggest that there is NO way to
->lower a severity rating with a design change.

If you approach it from the point of view of a system FMEA (as you now are) and your line item for the potential failure is a wheel falling off (due to whatever reason), you can change the design so that the severity of the effect of the failure (the wheel falling off) can be reduced. I can think of lots of ways - some of which would be pretty far fetched, but none the less...

[This message has been edited by Marc Smith (edited 18 April 2001).]

OK. I'll bite. (I almost made it a full 24 hour without breaking my self imposed moratorium on posting).

How does the severity of a wheel falling off ever change?

IF it falls off, it falls off.

Just as an aside, a few years ago, there was a jet that crashed. It was determined upon investigation that what had happened was that an engine blade came loose and cut through the primary and the two or three back-up hydraulic lines meant to provide control to the tail sufaces used to control the flight of the plane.

Now, I am sure that you could say that the original severity ranking for the effect of the main hydraulic line failing was decreased by the addition of the secondary and tertiary hydraulic lines. But, in the big picture, shouldn't the severity ranking of last redundant hydraulic line have inherited the high severity ranking for effect of potential failure: Loss of control surface articulation, if you will.
This real world, actually happened, example, I think, illustrates my contention that you don't really reduce the severity ranking with a design. Whether it is a safety razor, or a space shuttle.

Yes, I think in terms of systems. I think it is a bit naive to not think in terms of systems. I really believe that the low hanging fruit and the biggest bang for the buck(pardon the gratuitous usage of cliche) is in focusing on design changes that will reduce the occurence and detection rankings.

Obviously my focus on a system FMEA is incorrect as no responses have echoed my stance.

Many thanks for your tireless (not intended as a pun related to the lugnut issue) efforts to explain the logic to me.

Create a new design where you don't need any wheels. Then they can't fall off.

Let's take a different direction:

I start with acute pancreatitis. What is the mortality rate? <10% (death)

I increases to chronic pancreatitis. What is the mortality rate? >50? (death)

I increase to pancreatic cancer. What is the mortality rate? >99? (death)

Can I reduce the severity by acting upon O & D by redesigning my life style?

Yes

ASD...

[This message has been edited by Al Dyer (edited 19 April 2001).]

AHA!!!

The pancreas example is a good one to explain my position.

And you have included all the information that I need to explain myself!

Firstly, the severity rating for all three cases is identical:

Acute-P, chronic-P, and P-cancer have identical severity ratings. The rating is 10 because the POTENTIAL effect is death. And the potential effect is death regardless of how good the detection is.

In other words, if the patient dies, he/she is just as dead if the pancreatic condition (take your pick which one)was detected or not.

Your model also illustrates nicely that the occurrence of the effect is very different for the different conditions. As you have stated, the Ocurrence of potential effect are, <10%, >50%, >99%, respectively. So, let's give them O's of 1, 6 and 10, respectively. Now, I am going to say from this that my detection had better be good, near 100% for all three cases due to the high severity. I want to have a detection rating no higher than 1 for any of the potential failure modes (acute P, chronic P, P cancer).

What this does is effectively control my RPN.
Results:

RPN Acute=10
RPN Chronic=60
RPN Cancer=100

But, as you pointed out, Al, the severity of all three remain at 10 (the potential effect of failure:death).

HM

Ok guys, I Think "Help Me" has us backed up into a corner. I do believe he is corect in his assumptions.
From the book; Severity of effect 10
"Very high severity ranking when a potential failure mode affects safe vehicle operation and/or involves noncompliance with a government regulation without warning"

Having read and re-read this statement several times I agree with "Help Me", There is nothing one can do to lessen the severity ranking. You can design a vehicle, as someone mentioned, without wheels, but you haven't lessened the ranking you have eliminated it; and just replaced it with another ranking.
You can add dual wheels, but that only reduces the severity ranking on one wheel.

IMHO the answer is a careful review and analysis of the potential effects of failure before selecting a ranking.

Ok guys, I Think "Help Me" has us backed up into a corner. I do believe he is corect in his assumptions.
From the book; Severity of effect 10
"Very high severity ranking when a potential failure mode affects safe vehicle operation and/or involves noncompliance with a government regulation without warning"

Having read and re-read this statement several times I agree with "Help Me", There is nothing one can do to lessen the severity ranking. You can design a vehicle, as someone mentioned, without wheels, but you haven't lessened the ranking you have eliminated it; and just replaced it with another ranking.
You can add dual wheels, but that only reduces the severity ranking on one wheel.

IMHO the answer is a careful review and analysis of the potential effects of failure before selecting a ranking.

->Ok guys, I Think "Help Me" has us backed up into a corner.
->I do believe he is corect in his assumptions.

You may be backed into a corner but I'm not. You and Help Me are missing a couple of important concepts.

If you, for example, redesign the car with no functional wheels (let's say you use an air cushion) where previously the severity of a wheel falling off was 10 (possible death), the severity of a wheel falling off now becomes zero. If the car doesn't depend upon wheels any more (a design change), if you have a wheel (maybe as an ornanment) and it falls off its severity is now 4 or less.

In reality the re-design would effect the removal of the FMEA line item for a Potential Failure Mode for a wheel falling off, or, if a wheel is kept for 'looks', the Potential Effect would now probably be 4 or less - customer dissatisfaction.

->You can design a vehicle, as someone mentioned, without
->wheels, but you haven't lessened the ranking you have
->eliminated it;

It is a given that some design changes will eliminate a potential failure mode all together.

->You can add dual wheels, but that only reduces the
->severity ranking on one wheel.

That was what was originally being looked at. The line item for the Potential Failure Mode was Wheel falls off. From another point of view. You have a line item for a wheel falling off. You re-design the vehicle to have 2 rear wheels, two centre wheels and 2 front wheels. This design change will lessen the severity of any individual wheel falling off.

Yes,
You can lessen the severity of any one wheel falling off by adding more wheels. But, you still have to look at the POTENTIAL EFFECT of the redundant wheels falling off. Whether they fall off simultaneously, or one at a time without any detectable warning to the operator. Again, the high severity ranking will be lurking in some other part of the design. You can't get rid of it. At best, you can find a wall to throw it over so that the engineer of another system has to cintend with a high severity.

Replace the wheels with a cushion of air. Fine, the severity fo losing an ornamental wheel is relatively minor. But, you have also changed the "Item/Function". Once the function of the wheel changes, you have to go back and look at the sytem/component that replaced the original wheels' function. In this case, the air cushion system, or whatever. So throw it over the wall to the Air Cushion Engineer. Loss of air pressure severity ranking on his DFMEA HAS to be the same as the original ranking for losing a wheel.

->The severity applies to the EFFECT only. The effect of a
->given failure will not change unless you change the design
->of the system or part. In the parachute example, if the
->chute doesn't open, you probably die and therefore it is a
->10 (failure occurs without warning). No suppose I design a
->smartchute that has built in diagnostics that emits a loud
->audible alarm telling me it is not going to open...It
->still doesn't open, but warns me that I am about to die,
->therefore making it a 9 (failure occurs with warning.) If
->I take it a step further, and add a smaller backup chute
->that deploys, that allows me to land without dying, I can
->make a case for the severity being a 7 (Item operable, but
->at a reduced level of performance. Customer dissatisfied).
->
->The question of action should be based on the RPN, not
->severity only. I think your ISO organization is wrong if
->they are trying to force you to lower the severity just
->because it is a 9 or 10. We often have 9's and 10's on our
->DFMEA's because many of our products effect safe vehicle
->operation or a government regulation. If the severity is
->high, we at least think about any changes that might be
->made. Often times, we have no control on what the vehicle
->does when our parts fail...this is determined by the car
->companies and we all know they are infinitely wise in
->areas of quality and safety. If changes are not feasible,
->we then focus on occurrence and detection (See my post
->much, much earlier in this string on what our procedure
->is) to bring the RPN into an acceptable level.

Well said and concise. I wish I had said that!

Just as an aside,

The AIAG FMEA manual designates (both on page 13 for DFMEA and page 35 for PFMEA) that the severity rating can be modified for specific parts/products as long as the group agrees on the criteria.

??????????

ASD...

Al,

You are correct. I always make sure the team agrees and that the criteria is DOCUMENTED. I also try to make sure they stay within the 10 point scale and cover 1-10.

Thanks,

All along, through my posts I have been saying that a high severity ranking (which, by definition, is the ranking of the severity of the effect of the potential failure-I think I got ripped once for looking at it in this way)is an indication that specific attention should be given to reducing the occurrence and detection rankings, therefore the overall RPN.

I think I referred to this as "Low hanging fruit." And, I would suggest that all the horns and secondary chutes actually, on a system level, do just that. They reduce the occurrence of the mechanism of the potential failure, and provide a means of detection of a failure. So, the redundant systems are a fantastic way to lower an RPN with design changes. But, if I remain cognizant that these items only will come into use if the main system fails, I must also be prepared to address what happens if the back-up systems (ABS, stability control, horns, back-up chutes, and the like) fail. And in the vast majority of cases, the severity of effect of the failure (again, this is the definition of DFMEA severity)of the parent system is inherited by the child, or back-up system.

If I don't, at least, consider what could POTENTIALLY happen if all the wheels fall off,(btw, does anybody remember when I said this was hypothetical? Sometimes exaggeration helps make the point. eg. I'll bet the guy who designed the hydraulics on that plane never dreamed that the main and two back-up systems could be wiped out in one event, either. But, it happened.) I haven't really assessed the seriousness of the effect of all the failure modes. Again, I admit that the wheels falling off was an unlikely HYPOTHETICAL (I am sure I said that before. Didn't I???)

As for System FMEA/ Design FMEA goes, I can't help but look at designs in terms of systems. And the AIAG FMEA reference manual specifically states that, "End items, along with every related system, subassembly and component should be evaluated." So, I don't think I am off base by taking a systems approach.

Perhaps we must agree to disagree on whether or not a severity ranking for the effect of a potential failure (the definition of DFMEA Severity)can be effectively reduced by a design change and get on with our lives.

I will stick to focusing on designs that will favorable impact occerrence and detection, esecially on the high severity items.

I thank all of you for your patience with me on this topic.

Good-bye

Help Me,

Don't say good-bye. Join the forum and post your opinions, we all need a wake-up call now and again.

ASD...

J.R. Strickland posted:"
In the parachute example, if the chute doesn't open, you probably die and therefore it is a 10 (failure occurs without warning)."

TRUE
"No suppose I design a smartchute that has built in diagnostics that emits a loud audible alarm telling me it is not going to open...It still doesn't open, but warns me that I am about to die, therefore making it a 9 (failure occurs with warning.)"

TRUE but the potential failure effect of the of the alarm becomes 10.

"If I take it a step further, and add a smaller backup chute that deploys, that allows me to land without dying, I can make a case for the severity being a 7 (Item operable, but at a reduced level of performance. Customer dissatisfied)."

TRUE, but the potential failure effect of the backup chute becomes 10; and so on through out the design phase.
The original potential failure effect was "the chute does not open" The ranking will never change but will only be carried over to each design change. IMHO

"The question of action should be based on the RPN, not severity only. I think your ISO organization is wrong if they are trying to force you to lower the severity just because it is a 9 or 10. We often have 9's and 10's on our DFMEA's because many of our products effect safe vehicle operation or a government regulation."

Refer to the AIAG FMEA manual pg. 21step 18 the last underlined sentence in the paragraph.

Sam,

Thank you!

I knew somebody out there had to understand what I was trying to say.

I agree wholeheartedly with the line you refer to from the manual.

And I think that comes through from my posts.


Tom

Originally ...

Refer to the AIAG FMEA manual pg. 21step 18 the last underlined sentence in the paragraph..........[/B]

I gracefully ask, what is your point?

The FMEA manual says we can define our own criteria and what do you consider high severity?

I think it is company specific and based upon customer requirements!

Does underlining a sentence that starts with "In General......." make a difference?

I will not go into the other subjects such as "shall", "should", "note", "as applicable" etc..............

ASD...

[This message has been edited by Al Dyer (edited 20 April 2001).]

Now you're going beyond common sense. Your original line item was 'the wheel falls off'. It was not 'every wheel falls off at the same time'.

If you will stick to the original line item, the design change will have reduced the severity of that failure mode or, as often happens, eliminated the specific potential failure effect. Your arguement is based upon trying to keep the potential effect of the potential failure.

You keep saying you still have to address the effect of the potential failure.
->But, you still have to look at the POTENTIAL EFFECT of the
->redundant wheels falling off.

Now you're talking a higher level. You're changing the subject.

One effect is for a given wheel to fall off. You want to now say, well, all the wheels might fall off so you have to address that. Well, maybe, maybe not. But let's say you you do want to address all wheels falling off at the same time. That is more of a system FMEA than a design or process FMEA. None the less, we'll say it's the line item you're concerned with.

Potential Failure Mode = All wheels fall off at the same time.
Potential Failure Effects = Car uncontrollable, possible death.

If I redesign the car to ride on an air cushion, the severity of all wheels falling off approaches zero.

->At best, you can find a wall to throw it over so that the
->engineer of another system has to cintend with a high
->severity.

Yes - sometimes there are tradeoffs. Sometimes not.

->Replace the wheels with a cushion of air. Fine, the
->severity fo losing an ornamental wheel is relatively
->minor. But, you have also changed the "Item/Function".

So? Is that somehow illegal? Please explain why that does that not count for reducing the severity of the effect of a wheel falling off. So what if you assign it to another system which can better handle the problem.

-> Whether they fall off
->simultaneously, or one at a time without any detectable
->warning to the operator.
This is not a valid arguement because that's not how FMEAs evolve.

I have never, by the way, seen a top level automotive FMEA (or lower level FMEA, whether design, system, or process) which has as a Potential Failure Mode of "Every wheel falls off at the same time". It doesn't happen in real life. One wheel - yes. Maybe even 2. But 3? Or 4?

Every month you hear of another stability function being added to cars. All wheel drive, ABS, electronic stability control systems - all of these reduce the severity of a wheel falling off. And they are all design changes.

I hesitated to dive into this one, but what the heck...

The severity applies to the EFFECT only. The effect of a given failure will not change unless you change the design of the system or part. In the parachute example, if the chute doesn't open, you probably die and therefore it is a 10 (failure occurs without warning). No suppose I design a smartchute that has built in diagnostics that emits a loud audible alarm telling me it is not going to open...It still doesn't open, but warns me that I am about to die, therefore making it a 9 (failure occurs with warning.) If I take it a step further, and add a smaller backup chute that deploys, that allows me to land without dying, I can make a case for the severity being a 7 (Item operable, but at a reduced level of performance. Customer dissatisfied).

The question of action should be based on the RPN, not severity only. I think your ISO organization is wrong if they are trying to force you to lower the severity just because it is a 9 or 10. We often have 9's and 10's on our DFMEA's because many of our products effect safe vehicle operation or a government regulation. If the severity is high, we at least think about any changes that might be made. Often times, we have no control on what the vehicle does when our parts fail...this is determined by the car companies and we all know they are infinitely wise in areas of quality and safety. If changes are not feasible, we then focus on occurrence and detection (See my post much, much earlier in this string on what our procedure is) to bring the RPN into an acceptable level.

Marc,

You posted:

...Every month you hear of another stability function being added to cars. All wheel drive, ABS, electronic stability control systems - all of these reduce the severity of a wheel falling off. And they are all design changes.

Thank you, severity can be reduced!!!!!!!

ASD...

Sam posted: "Refer to the AIAG FMEA manual pg. 21step 18 the last underlined sentence in the paragraph."

Yes, the OEM's get a little antsy when 9's and 10's are in FMEA's despite the fact many of them are driven by the system they own. (I wonder what the Firestone FMEA had in it?) If you look closely at my original post, I did say..."If the severity is high, we at least think about any changes that might be made." The actual verbiage in our internal procedure is "...Action plans will be considered and initiated, where possible, for the following FMEA conditions: 1) the top (highest) 3 RPNs, 2) a severity number greater than 8...). Why does it say "...where possible..."? I still stand on my claim that real action is based on RPN. What is a design team to do if they have a S=9,O=1,D=1 making the resultant RPN=9? My answer?...nothing, unless there is some easy and inexpensive change that can be made. My company's engineering resources will be better spent working on the other issues or designing the next product. In general I agree with the underlined statement on page 21, section 18. This doesn't mean I force my design organization into the redesign loop just because I have a 9 or 10.

As for the analysis of my scenarios, I agree that a failure of the main chute AND the alarm constitute a 10. I suppose one could make some argument as to the failure of the alarm itself being a 10, but I would put it further down on the scale. Most FMEA's don't take into account 2nd, 3rd, and 4th level failures in determining severities. While that would be nice, for complex products, it becomes an impractical exercise and none of us would want to pay the cost in sticker price for each part of a vehicle to take the FMEA to that level.

In the end, if I have a 10 and my design is so robust that my occurrence is a 1 and my design controls are so thorough as to be a 1, I move on and really worry about those items that have S=7,O=5,D=6,RPN=210 or 9 and 10 severities that do not have low occurence and detection ratings.

Help Me may be right about agreeing to disagree. However, I also read a lot of aggressive agreement in the posts.

I'd like some comments on occurance. The tables in the manual I've always had interepretted in PPM or in terms of the number of parts. When doing a process FMEA and looking at a process failure, is it also how often the event may occur? For example if there could be a set-up problem that you think occurs 1/20 set-ups, but only 1 piece out of the schedule run of 100,000 gets produced because 1st piece inspection catches it, is occurrance 1/20 or 1/100,000?

I have an opinion, but am interested in hearing some others first.

Well I'll step out on the limb here and say, IMO; that "occurrence" means "What is the probability that the potential effect will occur, not how many times it will occur" This can only be established by determining the confidence limits of your process, i.e., .90, .95, .999999.

-> This can only be established by determining the
-> confidence limits of your process, i.e., .90, .95,
-> .999999.

How about for a design FMEA?

I think in Laura's example, the set-up would be a "process function" and not related to occurance. Occurance is tied to the projected rate that the potential cause will occur.

Hopefully there is data (PPM, Scrap, Rework etc...) from past or current projects that can be used in the determiniation of your ranking of the occurance.

When thinking occurance don't consider effects or controls, think of causes.

ASD...

In Laura's scenerio, I take the stance that the occurrence stays at 1 in 20.

However, the first time inspection is the DETECTION, isn't it? Therefore, if the first time inspection is robust, the overall RPN will be driven down. So, in and of itself, the occurrence of 1 in 20 is not necessarily a bad thing. But it is a huge red flag to make sure that BOTH your detection is robust, AND make sure that your severity is reasonable. If you have a high severity and a 1 in 20 occurrence, I would think that the process may need additional tweaking.

HM

I tend to agree with Al. My first question is "What is a failure?" This may determine how you treat occurrence due to the specific cause. If you are addressing a specific product failure mode, then I would take the position that the occurrence is 1/100,000, not 1/20. You have 1/20 setups fail that result in 1/100,000 failed products. You can also think of it in terms of Cpk. Would you say your production process is incapable because your setup fails 1/20 times and generates 1/100,000 failures? I wouldn't. (I would still go fix my setup process anyway because a setup part still has $$$ associated with it.) I would evaluate my baseline process capability outside of any setup to determine occurrence.

JRS

Energy –

I think we are arguing semantics here. The FMEA manual states “The possible failure rates are based on the number of failures which are anticipated during the process execution”. In my own opinion the setup process is part of the overall global “process execution”.

Look at the broad picture as Al suggests. Base the occurrence value off historical performance data such as PPM, scrap or fallout from past or current projects.

I have watched many FMEA meetings get hung up on these types of questions. If no historical data is present, play is safe and score to the high side. Keep the FMEA alive, build some history and update as more data and history becomes available.

I am having a bit of trouble understanding this, I guess.

There are some assumptions being made by everyone regarding Laura's example. And, I think we maybe aren't making the same assumptions.

So, help me out Al and J.R. In your interpretation of the scenerio, what would be the process weakness, and what is the process control?

I guess I am looking at it as if the set-up is the weakness, and the inspection is the control. And I think of inspection as a type 2 control. The inspection doesn't really change the occurrence of a wrong set-up. It does, however, detect it.

It almost seems like you are considering the inpection as a type 1 control. Maybe that is acceptable.

Just different ways of looking at it, I suppose. I trust that you will let me know if I am off base.

HM

I guess I would look at the situation this way:

1: Process Set-Up Is A Process Funtion.

2: Oversized Diameter would be a Potential Failure Mode

3: Unable to process through next operation would be the Potential Effect Of The Failure.

4: Lack of set-up instructions would be the Potential Cause Of The Failure.

5: For Current Process Controls, setup instructions would be a Prevention Control, and 1st artical inspection would be a Detection Control.

The Occurance value would be derived based on #4 from above, the "Potential" occurance of the cause.

This is an over-simplified example.

Severity --- Potential Effect
Occurance --- Potantial Cause
Detection --- Current Controls (Prevention & Detection)

In Laura's example I don't see a reference to the cause of the failed set-up. There might be multiple causes which would call for multiple occurance ratings.

MHO

ASD...

So would it depend, then, on whether it is a set-up dependent(machining) or operator dependent(assembly) operation? APQP has alot of examples of different "types" of processes, but the FMEA does not.

My thoughts aligned with ASD - however the company did not want to be as specific as "would not assemble" as the effect. They preferred "parts out of spec" - because they are a machine shop and didn't necessarily know the detail of the effect. So each dimension wasn't specifically identified as out of spec - the entire operation was grouped as "parts out of spec." The customer rep was actually present, but also didn't know all of the effects, and the group really wanted to focus on eliminating the cause.

MHO? - the occurrance criteria being used should be established when you start out (we didn't do that). That the PFMEA manual is intended to be in terms of parts (rejects, PPM) and that it needs to be "changed" by company procedures if the processes are set-up dependent. I started out thinking 1/100,000 but changed to 1/20 - with the number off the table being the same - just modifying the criteria.

Laura,

Your statement:

MHO? - the occurrance criteria being used should be established when you start out.....

You have it in the proverbial nutshell!!!!

Thought Process!!!!!!!!!!!!!

ASD...

Originally posted by FMEA best:

yOU CAN NOT CHANGE THE SEVERITY OF DYING ONLY THE OCCURANCE OF IT HAPPENING OR THE DETECTION OF THIS THE WARNING SHUTE IS A DETECTION METHOD SO CHANGES THE DETECTION SCORE AND NOT THE SEVERITY. tHE SMART CHUTE IS WHERE YOU ARE REDUCING THE OCCURANCE OF SOMEONE DYING SO AGAIN YOU CAN NOT CHANGE THE SEVERITY OF SOMEONE DYING BUT YOU CAN REDUCE THE OCCURRANCE OR INCREASE THE DETECTION BEFORE JUMPING.Now you're just being silly. We're getting the same verbal gymnastics again.

Just because you can cite a case where you believe the severity cannot be modified does not extend to imply, much less prove, that in no case is this possible.

To those of you who still feel that you can never modify a severity rating through a design change, I suggest you write a paper and contact the ASQC and other related organizations. Every FMEA book I have read in the last 15+ years states this basic premise. I believe if you can prove your theory you will be the first to do so and will probably go down in 'quality history'. Your revelation will be a turning point and will profit you greatly. You will cause authors to rewrite their books and training companies will change their courses. As an example, you will force the AIAG to change their statements on pages 21 and 43 of their FMEA manual.

I am anxiously awaiting such a paper as well as agreement from your peers that your premise is correct. Until then, I personally will continue as I have for over 15 years - I will modify the severity of an FMEA line item through a design change.

yOU CAN NOT CHANGE THE SEVERITY OF DYING ONLY THE OCCURANCE OF IT HAPPENING OR THE DETECTION OF THIS THE WARNING SHUTE IS A DETECTION METHOD SO CHANGES THE DETECTION SCORE AND NOT THE SEVERITY. tHE SMART CHUTE IS WHERE YOU ARE REDUCING THE OCCURANCE OF SOMEONE DYING SO AGAIN YOU CAN NOT CHANGE THE SEVERITY OF SOMEONE DYING BUT YOU CAN REDUCE THE OCCURRANCE OR INCREASE THE DETECTION BEFORE JUMPING.

I agree Marc. I am sure we could come up with a lot of examples on real FMEAs where a design change HAS reduced the severity rating.

The topic was fun for a while, but as you say don't beat the dead horse here. Take it to somebody who cares.

Dave

It has been fun and, I believe, informative and thought provoking. And I remember years ago I had trouble with the concept until I had been on several FMEA teams. I admit I was a bit 'rough' in my last post, but -- geezzzzz. I also wanted to point out that this is not just my opinion.

Halo, I am new here in this interesting forum.
In column of 'detection' , if I want to rank based on the ability to detect the cause of the failure, how can I do that. The table in FMEA manual seems only for ranking based on the ability to detect the failure. Can I mix the two approach (rank based on detection the cause and detection the failure)? the rank will be very different.
Can anybody explain to me about this? thank you.

Dear Ibrahm,

Please see the discussion in the FMEA manual.

D ranking relates to the ability of your detection system, it doesn't matter if it to detect the cause or the failure mode.

So to my understanding you can use the same ranking table for the cause as well as the failure.

Good Luck
MSAFAI

Originally posted by MSAFAI:
Dear Ibrahm,

Please see the discussion in the FMEA manual.

D ranking relates to the ability of your detection system, it doesn't matter if it to detect the cause or the failure mode.

So to my understanding you can use the same ranking table for the cause as well as the failure.

Good Luck
MSAFAI



Be careful, the detection rating assumes the failure has already occurred.

Detection ratings apply to how well your current process controls will detect the failure.

I can't see where the Severity, Occurance, and Detection ratings can be interchanged.

MHO

ASD...

Dear Al,

I think there was a misunderstanding.

I was only talking about D-ranking table. I meant it can refer to the ability of a control method to detect a 'failure mode' or a 'cause'. (type 2 and 3 controls)

Regards,
MSAFAI

For MSAFAI and All Dyer, thank you for the reply. Maybe I need to explain my case more clearly. There is one failure mode, just say the wire color is red (I work in cable industry), the potential cause is too high temperature of annealing. S = 8, O = 6.
There are two Current process control in practice: check temperature 1 time per shift, and inspect 100 % of the product.
To find D:
If I use the first current control, D will be 5, so RPN = 240. Need action (I use RPN 100 as a limit)
If I use the second one, D will be 2, so RPN = 96. No need action.
What should I choose? In my opinion, I should lead my process to be failure preventive. So 100 % product inspection should be avoided. But according to the manual,that states that we can use type 2 of 3, It seems that we can choose the number of RPN. We want to high, use the second approach (in my case above). We want to low, use the first one. Am I correct?

Dear Ibrahm,

I think there are two methods to use:

1- Give a D number for the TOTAL control system (cause + failure detection)

2- Use the lowest D number.(this is what I prefer)

Colleagues, please comment which approach is better?

regards,
MSAFAI

If there are multiple process controls for a given cause, each of those controls should have its own detection ranking.

Under failure mode "xyz" I could have two separate causes.

I could have cause "A" that is controlled by 3 different controls. Each of those controls would need a separate detection ranking.

Cause "B" is controlled by 1 control method and would require 1 detection ranking.

I guess this all leads to the fact that we can have 1 failure mode that has multiple causes, controls, and RPN's.

As with all FMEA's, there is room for discretionary use with the knowledge that we need to be able to back up our reasoning for using whatever ranking systems we develop. The ranking systems in the AIAG are only guidelines as long as we keep it as consistant as possible.

ASD...

Thank you guys. Those makes me think about some ideas.

You're welcome!

Blast from the past. Anyone have anything to add?

If I use the first current control, D will be 5, so RPN = 240. Need action (I use RPN 100 as a limit)
If I use the second one, D will be 2, so RPN = 96. No need action.
What should I choose?

I think that the RPN number has a lot to answer for, as a lot of companies use this as a limit (around the 100 mark). Whilst I agree that the RPN number as intended is a useful tool for action prioritisation, we ( a T1 Automotive Supplier) go a little further and assign FMEA actions based on the following criteria.

1: High Severity (a severity rating of 9 or 10) including those rated as OS (operator safety).
2: Those with Internal / External significant characteristics.
3: High RPN (a RPN rating of >=100)
4: Other items identified by the team that could reduce a high occurrence or detection rating.

This increases the resultant actions from the FMEA but also ensures that High Severity items are also covered (more often than not the RPN for these is > 100 anyway), if the severity cannot be reduced from a resultant design change then the team must make a decision as to the management of the risk in production.

I would therefore recommend expanding your limits to look beyond just the RPN, even if no action is required, state this on the FMEA as agreed with the team and at least it shows that you have specifically reviewed the issue.

Another "methodology" I have heard of is using SxO for prioritizing. Using that approach, I would think, would "lead" you to have better detection implementation - at least for new products.

Bill

I have been doing FMEAs for design, equipment, and process for not an insignificant number of years, and the one conclusion I come to is this: variable data of any kind (whether a severity of 8 or 9 or 7.826, or an RPN or 99 or 101) is simply a feel good exercise with no real value.

Also, using severity if high, even though the RPN is fairly low, may mislead: since it is somewhat of a brainstorming exercise, nobody will be vetoed if they state the failure mode - "machine may spontaneously transmogrify into the likeness of Jabba the Hutt and suck all the air out of the shop"! It's severity is 10, but its probability of occurrence and undetectability is somewhere in the neighborhood of 0.000000001.

The REAL VALUE of the FMEA is the exercise itself - and the talent utilized to create it! It all comes down to one attribute. It is either an issue that will be addressed, or it will not be addressed. Period. So for each failure mode and probable cause, the group determines (naturally based on its S, O, D, or RPN - or gut feel) whether action is needed or not. If so, assignments, responsibilities, and target dates are established. The RPNs or S values MAY be used to prioritize tasks if there are many.

Allow me to curl up into the fetal position before the pummeling begins. :o

If there is any "pummeling", include me. I agree with Rob's statements.

The only issue I have is with the B3 and Tier 1s who have decided it's "their way (with their bogies) or the highway". IMO, they are the #1 CAUSE for FMEAs not being used in a manner useful to a company.

Bill
(Wow - that came out a bit stronger than I think I intended :eek: )

I wasn't around the first time this thread was discussed and found it highly thought-provoking. My question is "why tie the values to an arbitrary 10 point scale?" A severity of 10 is generally more than 10 times worse that a severity of 1. I know it would a big challenge to get the numbers, but why not come up with a score that really matters to management - some sort of cost/benefit analysis.

importance = (cost per occurrence) x (probabilty of occurrence) / income


If you can come up with good estimates, this seems to work wonderfully.

So for example:
1) Paracute school: with no backup chute, 1/10,000 jumps has a fatal error, which would cost $5.1 million (lawsuits and loss of future income). You make $200 profit per jump.
importance of main chute failure
= ($5,100,000) x (1/10,000) / ($200) = 2.55 = 255%
ie the expected cost of the failures is 2.55x your income and your net profit is $200 - $200*2.55 = -$310 per jump

with backup chute, 1/1,000,000 has a fatal error, but added expenses cut $40 out of your profit. Also, the lawsuit is less because you took appropriate precautions
importance of both failing
=($1,100,000) x (1,000,000) / ($160) = 0.0069 = 0.69%
importance of main failing
= ($10,000 in lost income) x 1/10,000 / $160 = 0.62%

i.e cost of failure = 1.3% of income, and your net profit is $160 - 0.013x$160 = $158 per jump.

2) Lug nuts: with 1 lug nut, you make $1000 profit per car, but you have a 1/10,000 chance per car that the wheel falls off and you loose a $5 million lawsuit. With 5 lug nuts per wheel, you only make $995 per car, but the odds of a lawsuit drops to 1/1 billion. You do the math.

Basically, change the severity scale from 1-10 to cost per failure, and change the occurrence scale from 1-10 to 0-1 (odds of failure).

Tim Folkerts

P.S. Two additional points. 1) The cost is not necessarily proportional to the # of failures. It probably costs Goodyear ~$100 to deal with one bad tire, but I'm sure it costs a lot more than $1,000,000 to deal with 10,000 bad tires. 2) Putting a price on human life can be difficult and politically incorrect, as Ford learned with Pinto gas tanks.

If there is any "pummeling", include me. I agree with Rob's statements.

The only issue I have is with the B3 and Tier 1s who have decided it's "their way (with their bogies) or the highway". IMO, they are the #1 CAUSE for FMEAs not being used in a manner useful to a company.

Bill
(Wow - that came out a bit stronger than I think I intended :eek: )

:agree:
Interesting that you mentioned the bogies / targets for FMEA here. I revisited the GM Statement of Requirements that their WWP group issued in Dec. 2002 which has a PFMEA bogey rpn number of 40 in their list of items suppliers are reuired to utilize / demonstrate / provide or get a signed waiver if they exceed rpn value of 40.

I believe the 40 RPN bogie is only for GM Powertrain (which, of course, we're tier 1 to).

Bill

I believe the 40 RPN bogie is only for GM Powertrain (which, of course, we're tier 1 to).

Bill
Yo are correct that it is currently only applicable to GM Powertrain, which I am happily not a Tier 1 to any longer.

"As a general rule, RPNs should be 40 or below. Processes showing RPNs over 40 must obtain formal written approval from your GM SQE." It is the requirement of GM Powertrain.

Who has the experience of " Processes showing RPNs over 40 must obtain formal written approval from your GM SQE."?

nancy chen

Who has the experience of " Processes showing RPNs over 40 must obtain formal written approval from your GM SQE."?
We don't have any PFMEAs that have every RPN under 40. The one part we supply Powertrain has very few under 40. I did not ask for "formal written approval". I told my SQE that the PFMEA had many RPNs over 40 and asked him if Powertrain was willing to cough up some money to help us get under 40 and he said "just submit it". Go figure :rolleyes:

Bill

Fantasic discussion: Some times the customer has "Prefered Method" of risk reduction activities, and some times they hide them in "Customer Specific Requirements" such as QSB (Quality Systems Basics) Attached is one of those "Perfered Methods" from the QSB work shop. I hope this is helpfull
Kind Regards:
Ragnar.

"As a general rule, RPNs should be 40 or below. Processes showing RPNs over 40 must obtain formal written approval from your GM SQE." It is the requirement of GM Powertrain.

Who has the experience of " Processes showing RPNs over 40 must obtain formal written approval from your GM SQE."?

nancy chen

Just launched a new program with GMPT and as with our previous 4 or 5 programs, our SQE provided us with a written waiver for the 40 target. Basically states we internally strive for RPN < 100 and have an active RPN reduction process to continually strive to push them ever lower. :whip:

"Target" RPNs are self-fulfilling prophecies. I strongly advise my suppliers against it, as the usual result will that the highest RPNs will be just below the target value. Common sense should always prevail.

Dear Sir,

Sorry for joining late, but this is response to Post # 1

We, in our Six sigma Project of Improving recovering efficiency in Copper recovery plant, have conducted a process FMEA to improve recovery, my observation is

# The issue with the higher RPN is to be addressed first , In my view these number only gives priority of taking action ,but do not leave any thing which has low RPN or are ‘trivial few’ after doing Pareto analysis.

# Severity in our case was more or less around 4. As safety was not an issue. Severity was to some extent a constant factor. So the reference given for page 43 for severity does not necessarily hold true.

Alok Bhatnagar
:thanks: