How Design of Experiments (DOE) Leads to Industrial Success

There may be a hidden factor that explains Japanese industrial success. While U.S. students of industry point to the cultural work ethic, the Japanese methods of management, the use of statistical process control, and the application of Just-in-Time manufacturing techniques, one key ingredient remains almost unnoticed: Genichi Taguchi’s System of Experimental Design, which uses laboratory techniques to improve factory productivity.

Design of Experiments (DOE) was developed in the quasi experimental design 1920’s by Sir Ronald A. Fisher of England. His techniques were first applied in agriculture. These classical techniques required modification to be applied in a complex industrial setting. Taguchi has been the primary contributor to upgrading experiment design methods for use in industry and design applications.

Taguchi, an engineer, has developed a very powerful way to help improve the quality of products while simultaneously lowering costs. Between 1950 and 1970 Dr. Taguchi’s methods of experimental design were developed at the Electrical Communication Laboratories (ECL), the Japanese counterpart of Bell Laboratories.

A notable application of these techniques was the development of a switch relay device. In 1971, the ECL beat Bell Labs to market with this device, completing the project with one-fifth of Bell’s personnel and one-fiftieth of its budget. Bell Labs invited Dr. Taguchi to explain his methods in 1972. A few years after the switch relay’s introduction, Western Electric stopped production of the device and began importing them solely from Nippon Telephone and Telegraph.

The Taguchi method is best described as an engineering tool with a statistical base. This approach is concerned with gains in productivity. Cost effectiveness is stressed, rather than statistical strictness. In the world of manufacturing, the classical assumptions of a detailed hypothesis, normality, or homogeneity of variance are generally impractical.

In manufacturing, cost savings are realized by the reduction of scrap, lowering of inspection costs, and minimizing rework losses. These savings are achieved through process improvements and variation reduction. Design cost savings are realized by reducing the delivery cycle and minimizing engineering design changes. Reducing total product cost is the ultimate goal.