Lean and Six Sigma

Whenever a process occurs, whether it is manufacturing a computer chip, drilling a hole in a piece of wood, or filing a piece of paper, there is a variance between the target value and what actually happens. When taken over a period of time or scaled on a large scale over many products, this variation causes problems with the end product. If a component of a product does not meet the required specifications, then it is naive to think that the product itself will function in the required capacity.

Six sigma is the strategy concerned with reducing the amount of variation concerned with completing a process on a repeated basis, so that the overall product can function at a level that is acceptable to the customer. It is also the practice of constant improvement by identifying defects that can be brought under control in order to improve the functionality of the end product. While it may seem like six sigma is a highly technical skill, in reality it is used in many different sectors. It is not uncommon to see six sigma practices implemented into marketing, sales, and customer support organizations as well.

Initially created and implemented by Motorola, most companies have implemented some sort of version of a six sigma program in most of their departments. There are some companies that even require all personnel to be trained in six sigma implementations and policies. It uses statistical methods integrated with quality and lean processes to measure the possible and recognized improvement in the process. If implemented properly, entire teams and sub organizational structures (i.e. black belts, green belts, etc) are implemented to guide personnel in the proper conduct of the six sigma process and bringing the culture to the workplace successfully.

The idea behind six sigma is revealed in the name of the process… through identification of sources of variation and cost, teams are formed to find what the sources are, and then the variation is measured and plotted. It is then analyzed to see if there are other, uncontrollable aspects of the data that may be effecting the way that the parameter is measured.

All of these are taken into consideration, and then the corrective action that is supposed to bring the process to within six sigma of the target value is implemented, or in other words, the process is improved. Over time, the process is conducted with the corrective action in place, and the parameter, once again, is measured.

This measurement is plotted, just as it was prior to the corrective action implementation, and the corrective action is analyzed for its effectiveness. The team then discusses what actions can be implemented to ensure the quality improvements are maintained and the progress is not lost by a lack of control over the corrective action.

The beauty of six sigma is that it can be used in any application, in any business, at any time. As stated before, there are plenty of documented case studies that show how six sigma can be effectively used inside of everything from sales and marketing to very complex manufacturing procedures. With the proper training and teams in place, the sky is the limit with regards to the amount of improvement an organization can realize by implementing the six sigma infrastructure. Six Sigma Explained

As can be seen in Figure (1), there are five basic steps to completing a six sigma project. The first is “Define”, in which the parameter in that will be the focus of the project is identified. Additionally, the impact to the bottom line of the business is discussed and the potential savings is measured. It is at this point in which the company will decide whether or not to pursue further action in the improvement of the parameter, and whether the time and funding spent toward the improvement will pay off in the end.

Next, the parameter is measured in the “Measure” phase. Statistic relevance is taken into consideration as well as other sources of variation such as gage error. It is determined how well the actual parameter can be brought under control by measuring it with respect to the sigma value of a normally distributed curve.

Take, for example, a process that has 1000 opportunities for a defect. Of these opportunities, 2 defects emerge. This obviously means the process has .002 DPO, or defects per opportunity. From that, we can figure out what our DPMO, or defects per million opportunities. To do this, we simply multiply the DPO x 1 million. Our process has a level of 2,000 DPMO. This means that for every million pieces of this product we produce, 2,000 of them will be defective.

From the DPMO and our DPMO/σ table, we find that our σ value is 4.37. By looking at Figure (2), you can interpret this to mean that you will have a 99.73% chance of having between 1,987 (-3σ) and 2,014 (+3 σ) defects for every 1,000,000 parts produced.

Six Sigma Curve


Figure (2)

Once this is completed, the team comes together and analyzes the data in the “Analyze” phase. If the previous two phases were correctly conducted, it will show where the greatest room for improvement exists, and the corrective actions are identified with the estimated improvement calculated.

Improvement is measured after the corrective action is implemented in the “Improve” phase. This phase is almost identical to the “Measure” phase, but more strong influence is placed on the corrective action’s impact on the final parameter variations.

Finally, the last stage is “Control”, in which the corrective action is either modified or changed such that a long term realization of improvement is shown. Many times the corrective action is temporary in nature and must be modified to be able to sustain the improvement.

While anyone can be taught to brainstorm and start six sigma projects, it should be noted that without a focused and well trained team, there is a very large possibility for failure inside of the six sigma project. It is recommended that a dedicated team be placed in charge of every project and assist the champion in making the project run smoothly.

Six sigma has been proven to set companies apart from each other with its effectiveness. It is practiced in almost every major corporation and almost always results in a better, leaner, and more proficient company.

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