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What is Six Sigma?

What is Six Sigma?
surrounding the drive Six Sigma quality are essentially those of statistics

and probability. In simple language, these concepts are reduced to: “How can I be sure that what I planned to really happen?” Basically, the concept of Six Sigma deals with measuring and improving how close we came to the delivery of what he intended to do.

Everything we do is variable, even slightly from plan. Since no result can match exactly our intention, we usually think in terms of limits of acceptability of what we plan to do. The ranges of acceptability of the limits of tolerance (or) to respond to the intended use of the product of our work-the needs and customer expectations.

Here’s an example. Consider how your tolerance limits may be structured to meet the expectations of customers in these two statements:

“Cut two medium potatoes into quarters of an inch. “and” Scan and press two quarter-inch holes in the carbon steel supports. “

What be the range of acceptability or tolerance for the quarter-inch value? (Tip: a 5 / 16 “cube of potato would probably be acceptable, a 5 / 16″ threaded hole probably not.) Another consideration in the manufacture of potato cubes and holes would be the inherent capacity of how that occurs the dimension of a quarter-inch-process capability. Are you hand-cut potatoes with a knife or are using a special cutting machine memory pages?
Is you drill holes with a portable drill or using a drill? If we measure complete enough cubes of potato and holes, the capacities of the various processes to talk to us. His tongue distribution curves.

The distribution curves tell us not only how well our processes have done, but they also tell us that the probability that our process is done. Statistical probabilities in group segments of the call distribution curve deviations mean standard. The symbol used for standard deviation is the lower case Greek letter sigma.

For any process with a distribution standard (something like a bell curve), the probability is 68.26% that the next value will be within one standard deviation from the mean. The probability is 95.44% of the value itself following are within two standard deviations. The probability is 99.73% which is within three sigma, and 99.994%, which will within four sigma.

If the range of acceptability, or tolerance for their product is at or outside the four sigma point on the curve of distribution for your process, you are virtually assured of producing acceptable material every time, provided, of course, that its process is focused and stays focused in its target value.

Unfortunately, even if its center can process at once, tend to drift. Experimental data show that most processes that are in control still drift about 1.5 sigma on either side of its center point in time.

This means that the actual probability of a process with the tolerance limits at four sigma, production of acceptable material is actually more like 98.76%, not 99.994%.

To get to close out perfect process, the curve for the process should fit within the tolerances so that the tolerances are equal to or more than six standard deviations, or Six Sigma, in the distribution curve. That’s why we call our objective of Six Sigma quality.

Quality makes us strong
In the past, conventional wisdom says that high levels of quality costs more in the long run than poorer quality, raising the price he had to ask for your product and make it less competitive. Balance Quality costing was thought to be the key to economic survival. The surprising discovery of the companies that originally developed Six Sigma, or world class the quality of the best quality is that it costs more. Actually costs less. The reason is something called cost of quality. Cost of quality is really the cost of deviating the quality they pay for things such as rework, scrap and warranty claims. Doing things right the first time, especially if the effort need to reach that level of performance-in fact it costs much less then the creation of finding and fixing defects.

Shooting for Six Sigma:
An illustrative fable
The rationale for Six Sigma quality involves some understanding of the role of statistical variation. Here a story about that. Robin Hood is in the meadow practicing for the archery contest to be held next week at the castle. After Robin 100 first shots Friar Tuck, Robin Master Black Belt in archery, adding the number of hits on target for each objective. Robin is considered successful in the bull’s eye 68% of the time.

Friar Tuck plots the results of target practice by Robin in a graph called a histogram. The results look something like this. “Note that the bars form a curve that looks something like a bell, “says the monk.” This is a normal distribution curve. Each process that varies uniformly around a central point of forming a pattern that resembles a smooth bell curve, if you make a large enough number of trials or in this case, shoot arrows enough “.

Robin scratches his head. Friar Tuck explained that the process involves selecting Robin straight arrows (raw material) to hold the bow steady and smoothly release the bowstring (human), wood of the bow and the force of the chain (machinery), and the technique of pointing to the center of the process in the bull’s eye (calibration and statistical process control).

The product of the process of Robin is an arrow on target. More specifically, products satisfy the customer are the arrows that counts. Arrows outside the third circle on these goals will not count, so they are defective. Robin process seems to be 100% within specification. In other words, any product made is acceptable in the eyes of the customer.

“You seem to be three to four sigma goalkeeper,” the priest continued. “We would holes that measure more to know for sure, but let’s assume that 99.99% of his shots score, which is four shots sigma. “Robin to tell progress to his merry men.

The next day, the wind is constantly changing directions, there is a slight haze. Robin believes that feels a cold. Either that is the reason, the process is not centered on the average of the way it did before. In fact, derives up to 1.5 Sigma unpredictable as both sides of the mean. Now, instead of producing flawless, after a hundred photographs, Robin has been a defect, a hole outside the circle of others. In fact, instead of 99.99% of his shot scoring only 99.38% do.

Although this may not seem like much has changed, imagine that instead of shooting at targets, Robin was laser holes in the turbine blades. Let’s say there were 100 holes in each sheet. The probability of producing a defect-free sheet would not be good. (Due to the creation of defects would be random, their process but there are some leaves and some sheets with multiple defects.)

Many times without control over all (not to mention spending a huge amount of rework and scrap), Robin, laser drilling, would be practically impossible to never give even a series of turbine blades drilled holes correctly.

Not only that the four sigma producers have to spend much time and money finding and fixing defects before the products could be sent, but since the inspection can not find all defects, it should also fix problems after they reached
the client. The Six Sigma producer, on the other hand, would be able to concentrate on only a handful of flaws to further improve the process.

How tools can help the Six Sigma quality? If the archer Robin were going to use these tools to become a Six Sigma shooter instead of a shooter than four sigma, where came out in the wind and rain, still do everything
The score ranges. Some arrows might now be in the second circle, but they all still be acceptable to the client, ensuring the first prize in the contest. Robin laser perforator also would succeed, he would be doing virtually defect-free turbine blades.

The steps on the road to Six Sigma quality:
1. Measurement
Six Sigma Quality means a level businesswide to less than 3.4 errors per million opportunities to make a mistake.
This quality standard includes the design, manufacture, marketing, administration, service, support all facets of the business. Everyone has the goal of equal quality and essentially the same method to reach it. While the design application manufacture of engines and obviously, the goal of Six Sigma-performance and most of the same tools apply equally to the softer, more administrative processes.

After the improvement project has been clearly defined and delimited, the first element in the process of quality improvement is performance measurement. Claims effective measurement of taking a statistical view of all processes and all the problems. This reliance on facts and logic is essential for finding Six Sigma quality.

The next step is knowing what to measure. The Sigma level determination is essentially based on the count of defects, so we measure the frequency of defects. Errors or defects in a manufacturing process tend to be relatively easy to define, simply a breach of a specification. For further the application to other processes and to further improve manufacturing, a new definition is useful: a defect is any breach of a satisfaction customer requirement and the customer is always the next person in the process.

At this early stage is critical to select quality characteristics will improve. These are based on an analysis of the needs of his clients (usually using a tool like Quality Function Deployment.) After clearly define its rules of and validate its performance measurement system (Gage with reliability and repeatability studies), then be able to determine the short term and long term capacity to process and performance of the actual processes of (Cp and Cpk).

2. Analysis
The second step is to define performance goals and identify sources of variation process. As a company, we have set of Six Sigma performance of all processes within five years as our goal. This should lead to specific objectives in each operation and process. To identify sources of variation, after accounting for the defects that should determine when, where and how they are produced. Many tools can be used to identify causes of variation that creates defects.

These include tools that many people have seen before (process mapping, Pareto charts, diagrams fish, histograms, scatter diagrams, run charts) and some that may be new (affinity diagrams, box and whisker diagrams, analysis Multivariate hypothesis testing).

3. Improvement
This phase includes the identification of possible causes of variation and discover the interrelationships between they. (The common tool in the design phase of the experiment or DOE.) Understanding these complex relationships, and then allows adjustment of process tolerances individual interact to produce the desired result.

4. Control
In the control phase, repeat the validation process and measuring system capacity assessment to ensure that the improvement was. The steps are taken to control the improvement process. (Examples of tools used in this phase are Statistical process control, testing and tweaking internal quality audits.)

Words of wisdom about the quality of
If you think it is natural have defects, and that quality is finding and fixing defects before they reach the customer, you are hoping to go out of business. To improve the speed and quality, must first measure it, and you should use a common measure.

The common business-level measures that promote improved quality are the defects per unit labor and cycle time per work unit. These measures apply equally to design, production, marketing, service, support and administration.

Everyone is responsible for the production of quality, therefore, all must be measured and responsible for quality. Measuring quality in an organization that pursues a type of aggression is the responsibility of improving operational management.

Customers want on-time delivery, a product that works immediately, there is first years of life failures and a product that is reliable in his lifetime. If the process is defective, the customer can not easily kept them for inspection and testing.

A robust design (one that is within the capabilities of existing processes for their production) is the key to increasing customer satisfaction and reduce costs. The form is a robust design through concurrent engineering and integrated design processes.

Because of a higher quality ultimately reduces cost, highest quality producer is more likely to be the lowest cost producer and, therefore, more effective competitor in the market.

About the Author

Steven Bonacorsi is a Senior Master Black Belt instructor and coach. Steven Bonacorsi has trained hundreds of Master Black Belts, Black Belts, Green Belts, and Project Sponsors and Executive Leaders in Lean Six Sigma DMAIC and Design for Lean Six Sigma process improvement methodologies.

Bonacorsi Consulting, LLC.

Steven Bonacorsi, President

Lean Six Sigma Master Black Belt

14 Clinton Street

Salem NH 03079

sbonacorsi@comcast.net

603-401-7047

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