Читать книгу Statistical Quality Control - Bhisham C. Gupta - Страница 45

The second definition of Six Sigma refers to a systematic approach to problem‐solving. The emphasis in Six Sigma is on solving process problems. A process is a series of steps designed to produce products and/or services.

As shown in Figure 2.2, the inputs to a process may include materials, people, or information. These inputs flow through the steps of the process, which produces a product or service as a final output. The concept can be applied to any industry or function. A manufacturing process may take raw materials and transform them into a finished product. In a front‐office process, invoices may go through process steps that then create vendor payments. A physician may order a series of tests, which finally leads to a diagnosis and treatment.

The Six Sigma methodology is driven by team projects that have a clearly defined purpose and specific goals. The projects concentrate on improving processes and have relatively short durations, with the majority completed within two to nine months. Project goals generally focus on reducing variation in a process and consequently reducing defects. Teams work together to accomplish project goals by following problem‐solving approach or five defined phases: Define, Measure, Analyze, Improve, and Control, (DMAIC, pronounced “duh may’ ik”), as shown in Figure 2.3.

Figure 2.2 Flow chart of a process.

Figure 2.3 The DMAIC cycle.

In the Define phase, a team sifts through customer feedback and product performance metrics to craft project problem and goal statements and establish baseline measures. Labor, material, and capital resources required by the project are identified, and a rough timeline for project milestones is created. This information is collected into a project charter that is approved by upper management.

During the Measure phase, the team identifies important metrics and collects additional data to help describe the nature of the problem.

In the Analyze phase, the team uses statistical and graphical techniques to identify the variables that are major drivers of the problem. In this stage, root causes of the problem are identified.

In the Improve phase, the team identifies ways to address the root cause(s) and prioritizes the potential solutions. Then, changes to the process are designed, tested, and then implemented.

In the final Control phase, the team works to create a plan to prevent the newly improved process from backsliding to previous levels of defects. Mechanisms for ongoing monitoring and control of key variables are also established at this point. During the project wrap‐up, the team’s success is celebrated, and the lessons that the team learned during the project are shared throughout the company so that other teams can benefit from their discoveries.