Six Sigma

What Does Six Sigma Mean?

Manufactured products have specifications that must be met in order for the product to be considered functional and useful. A product needs to fulfill a number of criteria that can often be defined numerically; for example, a nut needs a certain internal diameter and thread in order to securely fix onto a bolt. In statistics, if the “mean” represents the desired specification and the nearest specification limit can be defined as six standard deviations from the mean, then virtually all manufactured products will fit within this spectrum of quality and be considered acceptable. Any process that is said to operate with Six Sigma quality will produce a defect level of less than 3.4 defects per million opportunities.

Any quality management approach assumes that a cultural change can be achieved within the organization and commitment to achieving quality management can be gained from employees at all levels of the organization including top management.

Six Sigma and Sustainability

In order to work toward improving the sustainability of manufacturing operations, it is critical that energy and materials be conserved. When a manufacturing defect occurs, the product is unsuitable for consumption and waste is generated. While this waste may be recycled within the manufacturing system, there will be some embodied energy loss and additionally there may be some degradation of the material. By eliminating defects in manufacturing, and Six Sigma is one of the methods that can be used to accomplish this goal, materials and energy can be used more effectively.

History and Culture of Six Sigma

There is a rich history of quality management methods, and the culture of Six Sigma has grown out of approaches such as total quality management (TQM), zero defect, and quality control. What differentiates Six Sigma from previous quality management approaches is that it focuses on defined projects with specific objectives, with an emphasis on creating a human resource infrastructure within the organization of Six Sigma “black belts” and “green belts” to lead these projects. Six Sigma also seeks to integrate statistics and quantitative data into the process to ensure that the outputs are measureable, quantifiable, and verifiable, rather than making assumptions or guessing in relation to the gains that can be achieved.

One approach, which could be considered “traditional” for quality management in manufacturing operations, is for the workers on the production line to be responsible for ensuring that a consistent quality of product is produced, while analysis is performed, possibly by in-house statisticians after goods are produced, to analyze the “defect rate.” Six Sigma to a large degree “professionalizes” the role of quality management, and makes this a more overt role to be played within the organization. Quality management, rather than being an afterthought, becomes integral to all operations, with quality being managed by multiple employees at all levels of the organization, rather than as an afterthought.

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