Six Sigma methodology
“Six Sigma” is a complex part of the combined technology Lean 6 Sigma (lean management and 6 sigma). Lean Six Sigma is an integrated concept that combines the most popular concepts of quality management in the 1990s: Lean manufacturing, focused on eliminating losses and unproductive costs, and the Six Sigma concept, aimed at reducing the variability of processes and stabilizing the characteristics of products.
Six sigma is a production management concept developed at Motorola in 1986 and popularized in the mid-1990s after Jack Welch used it as a key strategy in General Electric. The essence of the concept is reduced to the need to improve the quality of the outputs of each of the processes, minimizing defects and statistical deviations in operating activities. The concept uses quality management methods, including statistical methods, requires the use of measurable goals and results, and also involves the creation of special working groups at the enterprise that implement projects to eliminate problems and improve processes.
The name derives from the statistical notion of the standard deviation, denoted by the Greek letter σ. The maturity of the production process in this concept is described as the σ-deviation rating, or the percentage of defect-free output, so the quality control process 6σ yields 99,99966% of the outputs without defects, or no more than 3.4 defective outputs per 1 million operations. Motorola set as goal the achievement of a quality score of 6σ for all production processes, and it was this level that gave the name of the concept. As a rule, in most processes at enterprises, the level of defects is within the framework of sigma analysis between three σ and four σ. This means that the yield of good products lies between 93.3 and 99.4%. With four sigma, the frequency of defects is 6210 cases per million. No one would be pleased if he belonged to 6210 clients who are the victim of a defective product or process. Thus, the Six Sigma method provides an opportunity, along with increased productivity, to also increase customer satisfaction. Six Sigma is a consistent, customer-driven and fact-based method of process improvement.
What does sigma mean in practice?
If the share of defective products supplied to the automotive industry is high, then from the point of view of system suppliers for the auto industry or manufacturers of equipment, two things are essential:
– “slippage” in the control leads to the subsequent use of defective products and can undermine the reliability of the production system or equipment;
– compliance with delivery dates may be in jeopardy due to additional processing and additional control.
From the manufacturer’s point of view, this is an additional cost for marriage and a reduction in opportunities to increase production capacity. In addition, many enterprises are going to require suppliers to return the additional costs they incur and / or to impose a ban on supplies for these suppliers.
The basic idea of six-sigma management is that if it is possible to measure the number of process defects, then it is possible to identify ways to eliminate defects, and thus to reach a quality level with a virtually zero reject.
Principles of “Six Sigma”
The practical application of the Six Sigma method involves the use of the most important principles:
– the desire to create a stable and predictable flow of processes to improve business performance;
– data and indicators characterizing the passage of production processes and business processes must be measurable, manageable and improved, and also reflect operational changes;
– it is necessary to actively involve the company’s employees at all levels, including top and middle management, to ensure continuous quality improvement;
– focus on processes instead of functional orientation, process management and continuous improvement of the process;
– management based on agreement on objectives;
– transparency of intra-corporate barriers, management without barriers.
Motorola offers a systematic way of implementing the Six Sigma method, which consists of five steps and is called DMAIC (English define, measure, analyze, improve, control):
- Definition of the project objectives and customer requests (internal and external);
- Measure the process to determine the current execution;
- analysis of defects, identification of root causes of defects;
- improvement of the process through the reduction of defects;
- control of the further course of the process.
In the US and Europe, this concept is used in many areas – in the industrial sectors, in medicine, in the service sector, in education, and even in the defense industry. The success of the Six Sigma concept gave birth to the desire to embrace other approaches in the form of this concept, continuing on the path of continuous improvement, or, more simply, to get ahead of competitors.