Let's fix Six Sigma!

Bev D

Heretical Statistician
Staff member
Super Moderator
#81
DPMO is the core six sigma concept. A defect occurs when a product or service is outside specification...As Bill Smith, the hero of six sigma, ironically pointed out, the specification can be anything you want it to be. DPMO can hence be anything you want.
Funny. Unfortunately not true. Bill Smith never wrote any such thing. (you have read his work, right?) In his articles he always defines defects as a failure of the product or service to meet customer expectation and/or as a failure of the product to function...additionally, his approach to design and process tolerances is always tied to ensuring that the product or service meets customer expectations and requirements; he did advocate a robust design that leveraged knowledge of true process capability such that the design tolerances were greater than the process variation in order to meet customer expectations with the fewest true defects. He also stated - as did others - that the more complex a design was the more likely a defect was to occur. Which is of course, true. He therefore advocated for variation reduction and robust simple as possible designs. In fact he advocated that the design process wasn't over until the manufacturing process reached high (true) quality levels holdign the designers accountable for meeting customer expectations. I see absolutely nothing wrong with waht Bill Smith actually wrote - not what other's claim he wrote.

It was the snake oil sales men who bastardized his - and other's - concepts - but they did make a lot of money:
It has been a great line for consultants approaching senior managers to say "I can absolutely guarantee that I will reduce your defect rates ! " How how impressive is that ... at least for anyone who has no understanding of the basics of quality. Approaches such as this have been used to milk companies of billions of dollars.
and there were similar consultants who jumped on the Deming/SPC bandwagon in the eighties. Did their actions and money grabbing make Deming or SPC flawed? No. They misrepresented Deming and SPC for their own gain. Oh well, such is the way of the world. Greed always wins in the short term...
 
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Helmut Jilling

Auditor / Consultant
#82
...I know that many companies who traditionally reported a defect rate of lets say 3%, got into the Six Sigma stuff, looked at all the 'opportunities for error' as the new denominator in their defect rate calculation, and then came up with a ppm figure based on that.

No process improvement had occurred, just a simple change in the metric.

Also with no clear description of either what constitutes a defect, or what constitutes an opportunity for a defect, the concept is somewhat open to abuse one might suspect ??

OK, that could happen. So what? Has any actual harm been done? They adjusted their number. If their purpose was to fudge numbers, they do not concern me anymore than guys who fudge their golf scores.

The real question is did they calibrate it to reflect a more accurate, noise-free baseline calculation, from which they will grow and improve, or did they just fudge a number?

If it is a more accurate number, then they can see more clearly how to improve their operations.
 

bobdoering

Stop X-bar/R Madness!!
Trusted Information Resource
#83
Now who sets the specification for a particular process, product or service ?
For "product specification" I would like to think it is the "Design Responsible" party. For "process specification", it would be the manufacturer.

[*]If someone else set the specification, would the specification be the same ?
It depends. Risk aversion, cost sensitivity, depth of process and function knowledge would surely bring people to different conclusions.

Do customers and manufacturers always set the specification at the same points ?
It depends. Although the "product specification" may be the same (as they are points) the "process specification" should be tighter (as they deal with distributions, and they are typically sampled, so they need to address sample error).

It has been a great line for consultants approaching senior managers to say "I can absolutely guarantee that I will reduce your defect rates ! " How how impressive is that ... at least for anyone who has no understanding of the basics of quality. Approaches such as this have been used to milk companies of billions of dollars.
I have made that claim for precision machining, and have shown it to be true. I can not claim to eliminate defects, thanks to special causes (e.g. broken tools), but I can reduce them with correct SPC (which, by the way, you will not find in Six Sigma books - yet. Sorry.) And, I haven't milked anyone for billions of dollars, yet. In fact, the info is all here in the Cove for free Statistical process control for precision machining. You can thank me later...

Counting defects and the specification based methodology is indeed the fundamental flaw in six sigma. The dozens of other flaws in six sigma follow.
I think if you know the conceptual difference between a product specification and a process specification, you may have a chance. As far as flaws, they are there. Normalcentricity is a popular flaw. Might want to deal with that.
 

Helmut Jilling

Auditor / Consultant
#84
...Reducing variation on the surface sounds great - but the down side is it can lead to overcontrol. Overtightened specification really can have a negative economic impact. Why pay more for tighter tolerances if the product performance is not improved? Who are you trying to impress with your target shooting skills? Painting the broad side of a barn with a paintball gun? :paint: Sure it's fun....but still....:rolleyes:

Do not define "quality" by specification or reduction of variation. Define quality by economic control - adjust your process only when you need to.

When debating the issue, be careful of picking sides. :nono: You may find occasions when one side is right and other situations when the other side is right. This just happens to be one example...

Hey...."It depends!" (Now that should be a Six Sigma concept, eh? :vfunny:)

I agree with much of what you said. I think sometimes the science gets in the way of common sense. When I started in Quality, I asked at what point you stop reducing variation in a particular process,and was told, "never." That did not makes common sense to me back then, and still doesn't even though I now have much more experience.

I agree different tools and different outcomes are appropriate, in differing situations. Sometimes we overcontrol.
 

Helmut Jilling

Auditor / Consultant
#86
...They were silly perpetuators of all kinds of myths and stupidity about SPC - but that didn't make SPC wrong. those people are leaches who have now moved on to 'six sigma' and are probably even now looking for the next blood source. Greed will always be with us. It does us no good to continually rail against it; we must focus our energies on the good we can do. We need to lead by example.

...Why don't we turn our efforts to doing some real good instead of "fighting the civil war" all over again?

Every industry has good and bad practitioners, even some charlatans - medical, real estate, politicians, Wall Street... Why should it surprise us that Quality has it's share.

I don't worry about that. I try to help people who want to learn how to achieve good results, and try to apply useful tools. And if I do that well, then I have earned my wages.
 

Stijloor

Staff member
Super Moderator
#87
Every industry has good and bad practitioners, even some charlatans - medical, real estate, politicians, Wall Street... Why should it surprise us that Quality has it's share.

I don't worry about that. I try to help people who want to learn how to achieve good results, and try to apply useful tools. And if I do that well, then I have earned my wages.
Well stated Helmut! :agree1:

The fact that the package and its label has been misapplied and abused, and sold as the ultimate quality solution, does not mean the individual tools contained in it are bad.

Stijloor.
 

Jim Wynne

Staff member
Admin
#88
Well stated Helmut! :agree1:

The fact that the package and its label has been misapplied and abused, and sold as the ultimate quality solution, does not mean the individual tools contained in it are bad.

Stijloor.
It's not just "charlatans" causing the trouble, although they're a significant part of the problem. It's all of the "practitioners" who feel confident in their use of the tools but have only superficial knowledge of them. There are no companies that use SS that I know of where there is real, verifiable evidence of the grandiose claims of money saved. There might be improvements, but often at the expense of inappropriate--and often unnecessary--use of statistical tools by people who don't understand what they're doing. Let's face it--DMAIC is just PDCA in an ill-fitting rented tuxedo.
 

Helmut Jilling

Auditor / Consultant
#89
It's not just "charlatans" causing the trouble, although they're a significant part of the problem. It's all of the "practitioners" who feel confident in their use of the tools but have only superficial knowledge of them. There are no companies that use SS that I know of where there is real, verifiable evidence of the grandiose claims of money saved. There might be improvements, but often at the expense of inappropriate--and often unnecessary--use of statistical tools by people who don't understand what they're doing. Let's face it--DMAIC is just PDCA in an ill-fitting rented tuxedo.

I won't denigrate the SS program, there are many people who get value form it. Are the results always 250,000 or better? No, of course not, but then, I never believed that part anyway.

There are many people who do it poorly, ham-handedly, with little knowledge. Poor practioners are found in every profession.

I do remember an article I read long ago touting the SS success at one particular company. They detailed all the $$$ improvements they achieved and were quite pleased and proud. Later in the article, they discussed how many people had been trained and all theinvestment they put in. I crunched some numbers and it appears they invested almost as much in training as what the improvements amounted to.

I think SS is worthwhile, as are all the other Quality tools. Let's justnot turn it into something more than it is, tools to achieve improvements.
 
E

e006823

#90
It's not just "charlatans" causing the trouble, although they're a significant part of the problem. It's all of the "practitioners" who feel confident in their use of the tools but have only superficial knowledge of them. There are no companies that use SS that I know of where there is real, verifiable evidence of the grandiose claims of money saved. There might be improvements, but often at the expense of inappropriate--and often unnecessary--use of statistical tools by people who don't understand what they're doing. Let's face it--DMAIC is just PDCA in an ill-fitting rented tuxedo.
I can tell you that AlliedSignal had "real, verifiable evidence of the grandiose claims of money saved".

The amount of games being played with metrics and savings all comes down to ethics and corporate culture. If someone is going to fudge numbers they’ll do with or without SS.
 
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