What's the difference between traditional quality mode and 6Sigma?

The traditional process capability quality model is essentially different from Six Sigma in the following two aspects:

1. The traditional model is only used in the manufacturing process, while Six Sigma is suitable for all important business processes.

The connotation of these differences is far deeper than most people can think. The application of Six Sigma in business process not only makes people adopt a new concept-treating manufacturing as a part of a large system, but also abandons the shortcomings of narrow and closed traditional methods. Consumers are not only concerned about how products are made. A series of factors such as price, service, payment terms, style, practicality, speed of updating and improvement, and technical support are all very important. Six Sigma not only benefits customers, but also the owners and investors of the company benefit from the improvement of unit cost-effectiveness and the shortening of product design cycle in the operation process. With the improvement of employees' productivity, their wages will also increase. Six Sigma covers a wide range, and all stakeholders of the organization can benefit from it.

2. The traditional model requires that the process standard deviation is only 1/6 of the total allowable deviation, while Six Sigma requires that the process standard deviation is112 of the total allowable deviation.

In essence, Six Sigma is a process quality goal, in which fitness is a statistical measurement of process change. It also belongs to the technical category of process capability. The traditional quality model holds that a process is capable if its distribution center is still within the engineering tolerance after adding or subtracting three sigma. Under the assumption of normal distribution, this three sigma quality level means that the process qualification rate is 99.73%. Later, the requirements for process center and fluctuation were further tightened, and the minimum acceptable condition was that the process average was at least four sigma away from the nearest project. Six fitness horses require that the items with the closest process mean be at least six fitness horses.

Six sigma is also suitable for processing discrete data, such as calculating the number of errors, which requires transforming the requirements of six sigma into corresponding qualified levels.

There is a puzzling thing about Six Sigma, that is, it claims that the unqualified rate produced by the operation of Six Sigma quality grade is 65438+3-4 million parts per million, which is recorded as 3.4ppm, but if you check the normal distribution table, you will find that the expected unqualified rate should be 0.002ppm (that is, 65438+2 billion parts per million). The difference between them is due to the assumption that the process average can be offset by plus or minus 1.5 sigma. The probability that the normal distribution falls outside the average of 4.5 sigma is exactly 3.4ppm. The process deviation of this order can be easily detected from a single sample through the control chart, so 3.4ppm represents the upper limit of conservative estimation of failure rate.

Compared with the quality of six sigma, the traditional quality standard of 99.73% means that the unqualified rate of 2700ppm is even without any deviation. If the production process consists of a series of steps, then the total qualified rate of this process is the product of the qualified rate of each step. For example, a simple process consisting of two steps, the pass rate of the first step is 80%, and the pass rate of the second step is 90%, so the total pass rate is 0.8x0.9=0.72=72%. Tianxingjian Enterprise Management Company pointed out that the total qualified rate of a process consisting of a series of steps will be lower than the minimum qualified rate of these steps. In a process consisting of 10 steps, if each step reaches the three sigma quality level, that is, the qualified rate is 99.73%, then the quality level at the end of the process is amazing: there will be 26,674 unqualified products out of 1 10,000 products! The complexity of modern production process determines that the production process is far more than 10 steps, so it is urgent to adopt six suitable horses, and the organization needs six suitable horses to survive. It is not only the multi-step manufacturing process that needs this extremely high quality requirement. Modern society urgently needs products and services with high quality and few mistakes, so Six Sigma came into being.