KPC & KCC verification and updates

#11
The severity of a failure mode remains high even though the occurrence may be low. To a nation of consumers, a failure rate of 1 ppm has low criticality. To the one consumer out of a million who is injured by a malfunction, the criticality is high. Process controls and error-proofing measures may reduce the risk of occurrence, but over time, changes occur which were never anticipated or countermeasures have a way of becoming removed or defeated. Someone once said, it is tough to make any design foolproof because they keep making better fools. Marking a KPC on a design document ensures that the potential risk is communicated and not overlooked, now and long into the future.

But that is why the PFMEA is a living document right? To mark a KPC solely on severity alone with the assumption that the occurrence will change over time may lead to way too much over-analysis. As of the current revision of the PFMEA, the supporting KCC to the KPC is well engrained in the process with such a low occurrence rating that to call it out as a KPC would be ineffective.

This is my position, the design engineer I'm working with shares your position. What are your thoughts on the overuse of KPC? Wouldn't that lead to uneconomical processing and increased customer scrutiny?
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#12
why does it matter to you? how would your work in manufacturing change if the characteristic was no longer a KPC?

what is your understanding / definition of a KPC? Why do you think it is there?

Why do you think there are too many KPC's? I seriously doubt that your Customer would be concerned about too many KPCs. too few KPCs would be a red flag, but not too many.
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#13
Look if you have appropriate controls in place to assure that the occurrence rate of a failure in the KPC is low to non-existent then you have done your job. the continued identification of the KPC on the drawing doesn't' require you to take additional action it only requires you to continue controlling the process. why does this bother you?
 

John Predmore

Involved In Discussions
#14
What are your thoughts on the overuse of KPC?
Since you ask, I think excessive use of KPCs is a negative reflection on the design engineer. The design engineer may have run out of lead time or may not know any alternative, which is a reflection on management. Overuse of special characteristics leads to a spiral of excessively tight tolerances, diminished process capability, excessive or redundant inspection, high scrap, high cost of manufacturing, dissatisfied customers, loss of competitive position, loss of business, loss of jobs and ultimately damage to our country's economic engine, which is predominately manufacturing.

In the century of Quality 4.0, quality professionals have a role to educate engineers and managers, and encourage quality by design, quality at the source. As Deming said, the transformation is everybody's job. Institute leadership.
 

GRP

Involved In Discussions
#15
I have spent many years in automotive and am familiar with the YCs and YSs from reviewing Fords FMEA handbook thoroughly.

I will have to check out the SCCAF form.

I just still feel as though there is no clear methodology of KPC revision based on PFMEA analysis.
Great, the SCCAF tackles in part the subject of KPC follow up. However you wont find an answer to the drawing and KPC issue.

In case you haven´t read it before, it might be interesting to also check FAP03-111, which is the procedure for identification, selection and control of SC.

My experience with this is that we got hit by a drawing with over 200 potential special characteristics. A lot of the significant ones we managed to avoid including in the control plan, based on knowledge of the process and demonstrated high capability.

That being said, and being at the receiving end of the workload, we didn´t think much of whomever created the drawing and we thought the design should have been more robust.

On the other hand, I would tend to agree with Bev D´s argument of leaving the KPCs in the drawing.
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#16
I agree that actual over use of special characteristic designations is a waste as you point out John. So is the underuse. The under use is actually more expensive as it leads to failures in the hands of the end user. Both are a result of poor design activity. When designers/developers don’t characterize the inputs of their design to the outputs (function) they are left with guessing.

On the other hand I have also experienced the same aversion to work from manufacturing who will try to reduce the amount of process controls.

Both are wrong and they are wrong to blame each other. I encountered this insanity when I entered the quality profession some 35 years ago adn I am pained to see it still in existence. In my experience it is the fault of engineers, managers and leadership. I also firmly believe that many of our standards - while well intended - drive us to the lowest common denominator of mediocrity resulting in more ‘contract lawyering’ than good engineering. Engineers should be asking “What is the right thing to do” not “what does the standard say”.
 

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