Can anyone define what Six Sigma really is?

[WALLACE]

This might be usefull

Here's a Visual map that I compiled a while back. It covers the basics of the Sick sigma stuff. Hope it's usefull to the discussion.
Wallace.

 

[J Oliphant]

learning about SS

.... Where I work, I have also seen the opposite extreme, that of people using less rigorous methodologies and wrapping the Sigma mantle around them in order to be able to claim their ROSS dollars and get recognition. Well, at least that was true until a recent crack down on Sigma rigor!

Beyond the rigor of the problem solving methods, I would also argue that the program structure of, at a minimum, distinct, peer reviewed, phases in accordance with DMAIC or DMADV, is mandatory. (Have you or any others here ever been invited to a "MAIC" phase exit review?!). The reason for this last point is that in order for these methods to add value, they need to be iterative in the proper sequence and not proceed to the next phase without adequate readiness.

The implications are that Sigma should be reserved for major improvements which would justify the adminstrative and program management overhead involved.

Mark

You know I think I'm seeing that rush to claim $$$. That makes the technique even more confusing, because instead of a process to eliminate variation- Its about claiming $$$.

I'm getting the book from my local library soon. thanks for all the replies, I realize you've been through these sort of threads before.

I think many of the more confusing aspects of six sigma, are a consequence of certain corporate decisions upon its implementation.

I recently passed CQE (found out today!) and I've been pondering whether SSBB is 'value added.' The way to find out is to genuinely learn more about it rather than just to look to how the corporation chooses to implement it.

Needless to say, since its a corporation-- its a given that some things will just not make a lot of sense.

have to agree about the comment with isixsigma. Makes me appreciate how generally polite and courteous cove members are.

 

[Bill Pflanz]

You know I think I'm seeing that rush to claim $$$. That makes the technique even more confusing, because instead of a process to eliminate variation- Its about claiming $$$.

I think many of the more confusing aspects of six sigma, are a consequence of certain corporate decisions upon its implementation.

J.
Now you are beginning to realize why SS is such a controversial topic with quality professionals. Executives are always looking for a quick fix that will be the answer to all their problems and SS is the latest. Its predecessors were TQM, Quality Circles, Reengineering etc. Besides his comments on management, many executives did not accept Deming because he did not believe in quick fixes. (There is no instant pudding).

I recently passed CQE (found out today!) and I've been pondering whether SSBB is 'value added.' The way to find out is to genuinely learn more about it rather than just to look to how the corporation chooses to implement it.Needless to say, since its a corporation-- its a given that some things will just not make a lot of sense.

Congratulations on your CQE. From your previous postings, it appears that you are considering a career change to the field of quality. Rather than spending more time on getting certifications, I would recommend doing some more individual studying in order to understand the history and philosophies of the various quality and management experts. If you are as passionate as you indicate, you will find lots of interesting readings that will educate you more than taking another ASQ test. This forum always has recommendations for what books to read and a visit to your local library will provide a free resource. Don't look for just quality books but also include leadership, team dynamics, communication, and other management books.

At the same time, you will need to make a decision on what you want to do with your life, including staying in the Butler area. There may be opportunities within your company, within your industry and the possibility of a total career change into a different industry, in a different part of the country

You sound like a smart person who is willing to learn on their own. It will take you some time but the journey will be worth it. Down the road, you could be the one answering questions in this forum as the expert. Just so we all keep are egos in check - I always describe an expert as someone who knows more than anyone else on a subject. Of course, if you know one thing and the rest of us know nothing than you are the expert.

Good luck.
Bill Pflanz

 

[QCAce]

I don't want to invoke the displeasure of KMAAA, so I will stick to a literal response to "what is six sigma".

In the beginning . . . Motorola was making electronic components and was having failures. The question was - how much work was needed on improvement? When are you "good enough". The theory was, if you keep improving the process until the centerline of the data is six standard deviations away from the specifications for the part, then this is the optimal place to be. Basically a Cpk of 2. That's it.

Hi Steve,

In a course I took at Univ of Wis, "Robust Tolerance Analysis," I was taught that you were allowed a 1.5 sigma shift from the centerline of your process for setup, and therefore you could be as close as 4.5 sigma to the nearest specification. This would mean a Cpk anywhere from 1.5 – 2.0.
I’m not sure if this was the original Motorola design or if it was some new six sigma thinking?

Andy 6/26/04

 

[Al Dyer]

Andy,

Respectfully, your teacher said it was allowed?????? By whom??? The customer doesn't expect a perfect product, but only one that fits in with all the other products that make up an assembly.

I guess just a difference between hypotheticals and real life.

Don't get me wrong, I believe in the process of 6S (continuous improvement), just not the marketing of it as another "saviour for industry".

Al...

 

[QCAce]

Al,

It was a course I had taken several years ago that taught the concept of process tolerancing. It was one of the best courses I had ever taken, but it was also taught as an approach to six sigma.

Not commenting on the pros and cons of 6S, I was just looking for comments from Steve or others to see if they had heard of the 1.5 sigma process average shift, and if this would then equate to a Cpk of 1.5.
What is six sigma? Is it +/- 6S or +/- 4.5S ?


Andy 6/27

 

[quasi_black_belt]

I've typically viewed the 1.5 Sigma shift as a reflection of tool wear and oddities such as qualification of not-quite-identical replacement sources for parts/materials/items which went end-of-life. Essentially, it is a fudge factor to encompass all the stuff that even the best sampling plan and experimental design could not explicitly capture as control factors / known variables.

 

[QCAce]

Sounds good Quasi,
I think our friend Steve might say from an SPC standpoint, you've identified known causes for process average shifts. We could make a note on our SPC chart, recalculate the control limits and move on, life is good .
But the question for me remains, when would you tell your boss that the process has achieved six sigma? +/-4.5S (Cpk = 1.5), +/-6S (Cpk = 2.0), +/-7.5S (Cpk = ?) ???

Andy 6/28

 

[Steve Prevette]

Hi Steve,

In a course I took at Univ of Wis, "Robust Tolerance Analysis," I was taught that you were allowed a 1.5 sigma shift from the centerline of your process for setup, and therefore you could be as close as 4.5 sigma to the nearest specification. This would mean a Cpk anywhere from 1.5 – 2.0.
I’m not sure if this was the original Motorola design or if it was some new six sigma thinking?

Andy 6/26/04

I have no direct knowledge of where the 1.5 sigma shift came from. I suspect it was because the normal distribution value at 6 sigma is SO small that managers did not find it palatable. I also believe it comes from misunderstanding SPC. With a full suite of SPC rules (not just a single point outside of the UCL/LCL) you will easily detect a 1.5 sigma shift in the average.

I still believe the original design was simply a Cpk of 2.

 

[Bill Pflanz]

I agree with Steve that if someone has an understanding of control charting, the shift is part of the normal process. If there is "tool wear and oddities" in the process, than the control chart is used to identify them. Whether you recalculate the limits to include these data points is dependent on how the original control limits were calculated and what you want to accomplish. If you want to use the control chart to detect the oddities, then I guess you would not use them in your control chart calculations and they would show up as outside the control limits. On the other hand, if tool wear and other oddities are part of the process, they would be included and the other control chart rules (besides being outside the control limits) would detect any shifts that would need to be investigated.

While studying for the ASQ SSBB exam, I did some research on the origins of the 1.5 Sigma shift. The following is an excerpt from Six Sigma - Understanding the Concept, Implications and Challenges, by Mario Perez-Wilson, who played a role in the promotion and implementation of Six Sigma at Motorola and is an explanation of the origins and reason for the use of the 1.5 Sigma Shift:

"Six Sigma is not 3.4 ppm. The whole misunderstanding about 3.4 ppm resulted from Motorola’s document “Our Six Sigma Challenge”. In it Motorola asserted if a process was made to be Six Sigma by having the design specifications be twice the process-width, the process would be extremely robust. Such a process would be robust, even if it was surprised by a significant or detrimental shift in average, as high as +1.5 sigma, the customers would not perceive a degradation in quality. At worst case, a shift of 1.5 sigma, would make a zero-defects product be 3.45 ppm and the customer would only perceive an increase from zero to 3 products defective, assuming a production run of 1,000,000. This was supposed to be the warranty Six Sigma processes brought to the customer, not actual ppm levels for Six Sigma.”

Bill Pflanz