Super hard alloy tools are manufactured by powder metallurgy methods. Powders of carbonized tungsten and other metal materials are obtained by wet mixing, pulverizing, and drying. These processes tend to generate aggregates and agglomerates, which must be removed by dry sifting of the powdered material. High processing speed, high yield, and high stability are important in sifting. These factors are linked directly with production costs, so there has been a need to find improved sifting conditions. Accordingly, the functionality of a dry sifter was studied, and a parameter design was simultaneously conducted to optimize the sifting conditions. The weight of the sifted powder was measured and verified by a new S/N ratio based on a chemical reaction. With this approach, however, measurement problems caused by the structure of the sifter were encountered, so a switchover was made to evaluation by the standard S/N ratio. The optimum conditions then obtained doubled the sifting speed and improved the yield by 20% in comparison with existing conditions.
An inexpensive and flexible technique for gripping devices with a robot hand was developed by applying a three-dimensional position measurement system (known as firefly catching measurement) developed in our research department. The features of this measurement system are that the target to be measured,which is a pattern marker with a density distribution, can be recognized with a low-cost camera and its three-dimensional position and orientation can be measured. In this study, an attempt was made to gain further accuracy by devising noise factors and establishing a measurement accuracy evaluation method using the S/N ratio. Through a series of parameter design exercises,positional recognition accuracy was improved by 16.1 db in terms of S/N ratio and by a factor of 6.4 in terms of true value.
Genichi Taguchi noted that the role of quality engineering was to free society from the need to predict, diagnose, and judge. The Limits to Growth, the initial report written by Dennis Meadows et al. for the Club of Rome, sounded an alarm regarding population growth and environmental destruction by stating that at present rates, mankind would reach a limit to growth within a century because of the exhaustion of resources and deterioration of the environment. Will this prediction come true? What sort of future society will the Earth have? Discussion of deviation from the true value in a world in which there is no true value was considered to be an ideal topic for quality engineering, in which the Mahalanobis-Taguchi system's error root mean square can be used to describe changes of the state of nations. The condition in which society finds itself was accordingly studied on the basis of the proposals made by the Club of Rome in The Lirnits to Growth. Examination of error root mean square distances by country and by year showed that different countries' conditions were revealed in their time-series trends.