"Six sigma" is a copyrighted process for problem identification and implementation of solutions. Six Sigma is a registered service mark and trademark of Motorola, Inc
The subject of a wide body of writings, put simply, Six Sigma is the application of the scientific method to business processes. Six Sigma derives its name from the statistical sciences. In those terms it represents a measure of quality that approaches perfection.
Where as a typical process in control will produce 99.7% defect free assuming that specifications are at 3 sigma, if the process is improved to the point where the specifications are at 6 sigma, defects are reduced to below 3.4 defects per million parts or opportunities. (Technically 3.4 ppm is the defect rate at 4.5 sigma, but given that the process may shift by 1.5 sigma, it has become accepted that a Six Sigma defect rate is; 3.4 ppm, although the actual defect rate for a perfectly stable 6 sigma process is 2-3 defects per billion.)
To summarize the processes known as Six Sigma it has two key methodologies: DMAIC (Define, Measure, Analyze, Improve, Control) and DMADV (Define, Measure, Analyze, Design, Verify). DMAIC is used to improve an existing business process. DMADV is used to create new product designs or process designs in such a way that it results in a more predictable, mature and defect free performance. Sometimes a DMAIC project may turn into a DFSS (Design for Six Sigma) project because the process in question requires complete redesign to bring about the desired degree of improvement.
DMAIC basic methodology consists of the following five phases:
Define - formally define the process improvement goals that are consistent with customer demands and enterprise strategy. Measure - to define baseline measurements on current process for future comparison. Map and measure the process in question and collect required process data. Analyze - to verify relationship and causality of factors. What is the relationship? Are there other factors that have not been considered? Improve - optimize the process based upon the analysis using techniques like Design of Experiments. Control - setup pilot runs to establish process capability, transition to production and thereafter continuously measure the process and institute control mechanisms to ensure that variances are corrected before they result in defects.
DMADV basic methodology consists of the following five phases:
Define - formally define the goals of the design activity that are consistent with customer demands and enterprise strategy. Measure identify CTQs (critical to qualities), product capabilities, production process capability, risk assessment, etc. Analyze - develop and design alternatives, create high-level design and evaluate design capability to select the best design. Design - develop detail design, optimize design, and plan for design verification. This phase may require simulations. Verify - design, setup pilot runs, implement production process and handover to process owners.
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This page last updated: 08/30/2011