Introduction to Six Sigma

Описание: Six Sigma is a customer-focused continuous improvement strategy for improving quality, productivity, profitability, and market competitiveness. It is focused on reducing variation using a problem-solving approach and statistical tools. Six Sigma was developed by Motorola in the mid 1980's and Bill Smith coined the term "Six Sigma" in 1986. Jack Welch incorporated Six Sigma in his business strategy at General Electric in 1990's. Since then, the Six Sigma methodology has expanded to manufacturing, service, healthcare, and many other industries.

Six Sigma aims to minimize defects and variation to a level of 3.4 defects per million opportunities in product design, production, and administrative processes. It is also a methodology using a metric based on standard deviation. A process that is at a six sigma level is 99.99966% defect free or 3.4 defective parts per million. Six Sigma projects are carried out using a five phase methodology called Define-Measure-Analyze-Improve (DMAIC).

Six Sigma targets aggressive goals. The goals of Six Sigma include developing a world-class culture, developing leaders, and supporting long-range objectives. There are numerous benefits of Six Sigma including a stronger knowledge of products and processes, a reduction in defects, an increased customer satisfaction level that generates business growth and improves profitability, an increased communication and teamwork, and a common set of tools.

Define - The purpose of the first phase of the DMAIC process is to identify and refine a process in order to meet or exceed the customer’s expectations. In this step it is important to clearly articulate the business problem, goal, potential resources, project scope and high-level project timeline. This information is typically captured within project charter document. The Define phase includes developing the following: the project charter, critical-to-quality characteristics, a problem statement, a communication plan, the project scope, and goal statements.

Measure - The purpose of the Measure phase is to develop, execute, verify a data collection plan, and objectively establish current baselines as the basis for improvement. The performance metric baseline(s) from the Measure phase will be compared to the performance metric at the conclusion of the project to determine objectively whether significant improvement has been made. It is usual for teams to invest a lot of effort into assessing the suitability of the proposed measurement systems. Good data is at the heart of the DMAIC process, which is why this phase is critical. The tools typically used in the Measure phase are: process flow diagrams, supplier-input-process-output-customer (SIPOC) diagram, value stream mapping (current state), waste analysis, failure mode and effects analysis (FMEA), and measurement systems analysis (MSA).

Analyze - The purpose of the Analyze phase is to develop and test hypotheses about the causes of process defects; specifically, the objective is to identify, validate and select root cause for elimination. A large number of potential root causes (process inputs, X) of the project problem are identified via root cause analysis (for example from a fishbone diagram). The top 3-4 potential root causes are selected using multi-voting or other consensus tool for further validation. A data collection plan is created and data are collected to establish the relative contribution of each root causes to the project metric, Y. This process is repeated until "valid" root causes can be identified. Tools commonly used in the Analyze phase include: cause and effect diagram, pareto chart, brainstorming, cost of poor quality, confidence intervals, regression analysis, and hypothesis testing.

Improve - The Improve phase focuses on identifying, testing, and implementing process improvement ideas. Identifying creative solutions to eliminate the key root causes in order to fix and prevent process problems is important in this phase. Tools in this stage include value stream mapping (future state), benchmarking, total productive maintenance, poka-yoke, single minute exchange of dies (SMED), and design of experiments (DOE).

Control - The final phase of the DMAIC process includes controlling and monitoring the process to sustain the gains achieved. In this phase it is important to create a control plan, update documents and processes, and provide appropriate training on the revised process. In particular, a control chart can be very useful to assess the stability of the improvements by providing a guide to monitor the process and a response plan in case the process becomes unstable. Tools commonly used in the control phase include control chart, statistical process control, standard work, visual management, communication plans, and standard operating procedures.