Design of Experiments

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DOE - Design of Experiment

DOE is an approach used to identify factors/steps that are contributing most to an observed variation in product specifications. The classical DOE focuses on identifying the factors that affect the level of a product/process response, examining the response and forming the mathematical prediction model. The modern DOE, introduced by Genichi Taguchi in early 1980s, applies in both product and process development to identify the factors that affect the variability of the response. One important use of DOE is to find the tolerances and nominal values, called Parameter Design, that will achieve design goals. In Taguchi method, it is to make the performance as insensitive as possible to variations of parameters that cannot be controlled easily. Allowance design is where tolerances are found for each parameter. Tolerances are larger where variation has little affect on performance. On the other, tighter tolerance, which are costly, are specified for parameters having variation that greatly effects performance. The premise behind this method is that the amount of variation in the performance of a design is affected much more by some parameters than by others. Also, the amount of variation in performance may possibly be changed by choosing different nominal values. Tolerances can be relaxed on those parameters without affecting the performance a great deal. Figure below shows an example of this. However, some parameters must not vary from the nominal value too much. If they do, there will be a large variation in the performance. For this, the design is said to be very sensitive to the parameter. In the figure, such a parameter is labeled as width. On the other hand, some parameters can vary a great deal from nominal and have little effect on performance. For this, the design is said to be not sensitive to the parameter. This is shown by label height in the illustration. Tolerances will be tight for the parameter labelled as width, but can be looser for height. [pic]

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Defect

Defect is defined as any variation from the requirements of the specifications, drawing, contract or order. It can be classified into the following categories: Critical Defect: A defect that could result in hazardous or unsafe conditions for individuals using or maintaining the product. In addition, critical defect may result in the loss of a tactical function of the product. Major Defect: A defect that could result in failure or reduce the usability of the unit of products for its intended purpose. However, major defect does not endanger individuals using the product, or result in the loss of a tactical function of the product. Minor Defect: A defect that does not reduce the usability of the unit of product from its intended purpose. Minor defect is merely a departure from established standards having no significant bearing on the effective use or operation of the unit. Back to Original Page

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Defect Rate

Defect rate, commonly written as a percent defective (%), can be measured by counting the number of defects per hundred items of product or service under consideration. Back to Original Page
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Deming Prize

Deming Prize is the most coveted award a Japanese company can win. In fact the standards that must be met in order to win this award are so difficult & so strenuously applied that some people are now questioning its high price. The coveted Deming Prize are awarded each year in Japan to the company that has achieved the greatest gain in quality and to an individual for developments in statistical theory. Back to Original Page

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Deming's 14 Points

Deming's Fourteen Points is a summary of Dr. Deming's philosophy on quality management. It describes what is necessary for a business to survive and be competitive today. The fourteen points are: 1. Create constancy of purpose toward the improvement of products and services in order to become competitive, stay in...
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