The above posts dealt with the measurement of variation, specifically with Cp and CpK parameters. This section will concentrate on more powerful statistical techniques, generally called Design of Experiments or DOE. They are particularly important in two areas: (1) for resolving chronic quality problems in production, and (2) at the design stage of [...]
The only surefire method to eliminate waste is to design a product and its process so that the parameters of interest to consumers are brought close to the target value or design center. There is no other way to get 100% yields or to achieve zero defects. Once this is done, production becomes [...]
Frank Satherwaite was a brilliant statistician who establish the theoretical underpinnings for Pre-control. Pre-control was further developed by the consulting company of Rath and Strong. The mechanics of Pre-control can be taught and less than 10 minutes as there are only four simple rules to follow as exemplified in the “Pre-Control Example” figure: [...]
Control Charts are the last of the elementary seven tools of QC. Because of its wide use and misuse, a good portion of this section will be devoted to it. In the minds of many, quality professionals and nonprofessionals alike, the control chart is synonymous with statistical process control. For a number of [...]
Although many companies have abandoned SPC tools for the more powerful DOE techniques, there are exceptions. Major exception is they have trained their entire direct labor force in elementary SPC tools so they can tackle low-grade quality problems. The result is instead having a few professionals tackle these problems, they now have a [...]
This section will briefly outline elementary statistical process control tools. There are three major techniques to achieve quality, the traditional approach, statistical process control, and the design of experiments. Traditional quality control consists of ineffective methods such as brute force inspection, management exhortation, delegation of quality responsibility to a detached quality control department, [...]
In every manufacturing operation there is variability. The variability becomes evident whenever a quality characteristic of the product is measured. There are two basically different reasons for variability, and it is very important to distinguish between them. Normal Distribution Variability Inherent in the Process occurs even when all adjustable factors known to affect [...]
Ellis Ott in his book on Process Quality Control pointed out that every manufacturing operation has problems. Some are painfully obvious; others require ingenuity and hard work to identify. Every research and development person, production engineer and supervisor has to be a troubleshooter. Anyone hoping to become a research and development person, production [...]
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