6 Sigma is an improvement methodology developed to reduce variation in processes. Like Lean, Six Sigma is like a toolbox containing many Operational Excellence tools. Although a small part of 6 Sigma tools are also used in Lean, it mainly consists of Problem Definition, Problem Solving, Data Analysis and Statistical Methods. Six Sigma is mostly used to solve complex problems of quality.
For example, the diameters of some of the bolts produced are not within the desired tolerances, which can be easily solved with the the Six Sigma Method.
WHAT IS VARIATION?
Variation is basically not consistently getting the same results from the output you expect from the process (quality, efficiency, etc.) There are two types of variation in a process:
- Centering Problem (left): When the desired parameter is above and / or below tolerances (or specification limits) it is called the centering problem. For example, the process runs slower than desired, the drill bit pierces above the set value, the fabric is darker than the color we want.
- Scattering Problem (right):The situation where the desired parameter is scattered over larger than desired area is called the scattering problem. For example, the cycle rate for the same product varies at different times, the color tones in different meters of the fabric are different.
There may be situations where both occur at the same time.
Variation exists in every process. The sources of variation may be due to known reasons (your journey to come home, which takes 30 minutes on average, took 45 minutes due to snow) or the natural oscillation of the process (sometimes it may take 30 minutes, sometimes 32 minutes).
For this reason, since it is known that the product desired to be produced as 30 microns in the example below cannot always be produced at this value, tolerances (specification limits) have been established.
When your process goes beyond these limits, it produces erroneous output. The more you reduce the process variability, the less likely you are to produce faulty output. This will increase customer satisfaction.
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