what percentage of a normal distribution is contained within six sigma?

how many sigma are there?

what is the difference between six sigma projects and poka-yoke error proofing. poka-yoke seems to be for creating zero defect product, and six sigma for reducing the amount of nonconforming product through discipline and study.

can someone give me some examples of different industries or products that would be clearly a subject of error-proofing or alternately six sigma?

“what percentage of a normal distribution is contained within six sigma?”

approx. 99.9999999009878 %

”how many sigma are there?”

I’m not sure what you mean with this question. How many sigma are there where?

”what is the difference between six sigma projects and poka-yoke error proofing. poka-yoke seems to be for creating zero defect product, and six sigma for reducing the amount of nonconforming product through discipline and study. can someone give me some examples of different industries or products that would be clearly a subject of error-proofing or alternately six sigma?”


Six Sigma is the realization/recognition of upper management that customer oriented quality is important. Six Sigma emphasizes a disciplined data oriented approach to problem solving (DMAIC/DMADV methodologies). In application the emphasis is on meaningful metrics, a common language, training at all levels of an organization and a team approach to problem solving. Six Sigma incorporates other methodologies/tools such as QFD/Poke-Yoke/Lean. As a methodology it is applicable to any process, and it’s use is expanding beyond manufacturing and transactional business applications to government, schools and hospitals. I believe that you would use at least some of the Six Sigma methodology (Define/Measure/Analyze/Improve/Control) prior to implementing a poka-yoke solution. It would be up to you and your company when to use what tool. I would just caution you to use what is practical for a given situation.

Regards,
Bob

Bob

thank you for your response. I am very interested in these tools and their application in automotive type industry. whether it be hydraulic hand pumps or irrigation water tanks or actual automotive hardware, I want to use these sophisticated tools for our sophisticated customers.

are you familiar with machined hardware as provided by a job shop? with this, I am talking about custom hardware as specified by a TS-16949 organization in quantities of 200-1000000 and about 60% repeat part number manufacturing.

what sort of tools would you leverage in this type of operation?

would AIAG FMEA, APQP and control plan, SPC, and MSA be considered six sigma quality tools? are these tools adequate for DMAIC disciplining?

what is QFD? are there other tools you would recommend incorporating into the operations of a job shop in the process of becoming an automotive class supplier?


Erik

atetsade,

When talking about 6 Sigma you must consider the WHOLE process, not the product (or manufacturing) in isolation.

Is poke-yoke literally "error proofing" and does it result in zero defects?

Is poke-yoke literally "error proofing" and does it result in zero defects?There are plenty of web sites devoted to poke yoke and "mistake proofing" - use Google to find and sample a few.

In nearly forty years of being in or on the fringes of Quality as a profession, I can tell you truly I have never seen an organization with Zero Defects, regardless of its methodology (or its advertising.)

What you DO see with mistake proofing is a new way of looking at processes. Essentially, we try to eliminate as many chances for failure as possible.

Think of training wheels for a kid's two-wheel bike. Options for failure without training wheels include

kid falls and gets injured
kid falls and damages bike
dad running along side to prevent falling has heart attack
The reality is there can still be failures with training wheels

ride in front of car or truck
smash into a person and injure him/her
snag a training wheel or its frame on an obstacle

I’m very familiar with machined hardware; however I’m not too familiar with the requirements of TS-16949.

The limited familiarity (I’ve read the AIAG manuals) I have with APQP leads me to believe that the tool set used in Six Sigma is also used in the APQP process. The difference that I believe is present is that the APQP process is done upfront and the Six Sigma methodology is usually applied as part of a continual improvement program.

Quality Function Deployment (QFD) is a methodology for taking the Voice of the Customer and using that information to drive aspects of product development. There is some good information on the Cove about QFD and also at this website: http://www.qfdi.org/what_is_qfd/what_is_qfd.htm



“Is poke-yoke literally "error proofing" and does it result in zero defects?”


There are four types of mistake proofing that I’m aware of:

Elimination: Redesign the system to eliminate the chance of the error.

Facilitation: Provide methods of guidance, hard and soft, to minimize the chance of an error.

Mitigation: Lessen the effect of the error if the resulting defect gets to the customer.

Flagging: methods that ensure 100% chance of capturing and removing all defective units prior to shipment.


http://www.campbell.berry.edu/faculty/jgrout/tutorial.html has some good info on poke-yoke and some more can be found at http://www.isixsigma.com/library/content/c020128a.asp, and
http://www.isixsigma.com/library/content/c020828a.asp


I may sound cynical but I don’t believe that poke-yoke will result in zero defects, if for no other reason then Murphy’s eleventh law: It is impossible to make anything foolproof because fools are so ingenious. It is however in my opinion a big step in decreasing/limiting the amount of defects.


You asked about what sort of tools would you leverage in your operation. It depends on what you have in place and what you are trying to accomplish. Are you focusing on process improvement or TS-16949 compliance?


Bob

“what percentage of a normal distribution is contained within six sigma?”

approx. 99.9999999009878 %



Just two quick comments:

1) FOR GENERAL INFORMATION: When you talk to six sigma people, this isn't the answer you get. For a variety of statistical and/or practical reasons (no one seems to be really sure quite why), six sigma people really only claim a 4.5 sigma quality level, or 99.999966% = 3.4 PPM

2) FOR STATISTICS PURISTS: The fraction of the normal distribution no more than n standard deviations above the mean can be looked up in a variety of tables, or you can use an Excel function =NORMSDIST(6). This gives the result quoted above. You really should, however, also consider the fraction that are at least 6 standard deviations below the mean. This will double the # of defects, so the correct answer should be
not 99.9999999009878 % (0.00099 PPM)
but 99.9999999019756 % (0.00198 PPM)

(As if anybody but me would ever worry about such a miniscule difference!)

Tim

six sigma people really only claim a 4.5 sigma quality level, or 99.999966% = 3.4 PPM

6 sigma "Short Term" = 4.5 sigma "Long Term", this takes account of the 1.5 sigma shift over time.

Just two quick comments:

2) FOR STATISTICS PURISTS: The fraction of the normal distribution no more than n standard deviations above the mean can be looked up in a variety of tables, or you can use an Excel function =NORMSDIST(6). This gives the result quoted above. You really should, however, also consider the fraction that are at least 6 standard deviations below the mean. This will double the # of defects, so the correct answer should be
not 99.9999999009878 % (0.00099 PPM)
but 99.9999999019756 % (0.00198 PPM)

(As if anybody but me would ever worry about such a miniscule difference!)

Tim
Your correct, and I should have caught it before posting.

6 sigma "Short Term" = 4.5 sigma "Long Term", this takes account of the 1.5 sigma shift over time.
There is a lot of controversy within the “community” of Six Sigma practitioners about the use and validity of the “1.5 Sigma Shift”. In my opinion if it is used at all, it should be only used in the absence of real data as an estimate of long-term capability, as in a process start-up. The company I’m with always reports short-term Sigma levels, the Six Sigma goal refers to short term Sigma.

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 the best explanation of the origins and reason for the use of the 1.5 Sigma Shift I’ve seen:

“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.”


Bob

In our company we use six-sigma typically for improvements on manufacturing processes. Poka yoke on the other hand is typically uses at assembly processes.

On wikipedia you will find a good description of six sigma

Six_Sigma

as well as poka yoke

Poka_yoke

For poka yoke do visit Grouts homepage - it is a must

www.mistakeproofing.com

I would say poka-yoke can be used for nearly any process. With enough creativity you can mistake proof manufacturing, service, clerical, administrative, etc...

In our company we use six-sigma typically for improvements on manufacturing processes. Poka yoke on the other hand is typically uses at assembly processes.

Assembly is a manufacturing process.


I would say poka-yoke can be used for nearly any process. With enough creativity you can mistake proof manufacturing, service, clerical, administrative, etc...

Yes. Most processes are amenable to mistake-proofing, even ones that are completely automated.