In the development of machining center spindles, electric power consumption was measured and evaluated by use of the S/N ratio. When the S/N ratio was obtained, the ideal state was taken to be a proportional relation between rotational speed and electric power, and the evaluation was carried out using dynamic characteristics. However, from the results of actual electric power consumption measurements, it became clear that the relation is nonlinear for some types of spindle motors. The evaluation method was therefore changed to a method using the standard S/N ratio, and variability and linearity were evaluated separately. Experiments showed less temperature rise under the improved conditions than before the improvement, demonstrating that temperature can be decreased by electric power evaluation. Use of the standard S/N ratio also demonstrated the effectiveness of separating variability and linearity.

Drawing on the results of experiments with a hydraulic injection molding machine, experiments were carried out on an electrically powered injection molding machine to improve its mold-to-product transferability. The reproducibility of the transferability gain was about the same as with the hydraulic machine, which was not satisfactory, but this showed the limits of transferability. Data on the changing molding conditions obtained during operation of the molding machine were derived as patterns and used for analysis by the Mahalanobis-Taguchi system. It was shown that the process could be diagnosed from the aspect of the operating data of the molding machine and that, as with the hydraulic machine, whether molded products would be defective or not could be predicted.

In a previous parameter design study to improve the fuel efficiency of a car,guidelines for fuel-efficient driving were obtained, together with several findings concerning the fuel consumption behavior of cars. In practice, however, the optimal conditions obtained in the experiment were difficult to maintain in daily driving because of the effects of various other factors, including other traffic and the weather. An attempt was therefore made to predict actual mileage by bringing these varying factors into the experiment, by predicting mileage using the Both-sides Taguchi method with data obtained while the author drove to work. Predictive accuracy adequate for practical use was obtained. Effects on predictive accuracy were confirmed in cases such as when the unit space was defined using mean values of the signal data instead of being defined in the ordinary way. Through selection and diagnosis of specific items, it was objectively shown that frequent stops at traffic signals, wet road surfaces, and low temperatures lead to low fuel efficiency.

Laser sintering hybrid milling is a metal die manufacturing process that combines selective laser sintering with milling. The machine that implements this hybrid process runs unattended for extended periods of time, so the process must be monitored, diagnosed, and kept in a stable condition. The authors had already carried out a parameter design of the process conditions and studied their optimization. The next step, aimed at in-line process diagnostics, began with the proposal of diagnostic items and methods and an estimation accuracy study, using the two-sided Taguchi method applied to the waveform characteristics of electric power patterns for cutting sintered metal. The results showed the possibility of separating the experimental signals thought to be dominant in the diagnosis of abnormal conditions. In preparation for future diagnosis of abnormal conditions, it appears necessary to reexamine the issues, apply the methods to other types of metallurgy, confirm their validity, and study the posibility of in-line diagnostics on the actual machine.

With the world becoming digital, the photo imaging industry, like other industries, must now meet consumers' diversified needs accurately and promptly. As it is difficult for conventional development methods to deal flexibly with changes in specifications, agile development, in which customer requirements are incorporated as they arise, has become important. To promote agile development,our company has been improving our development flexibility by collaborating with software manufactures and importing their applications to provide functions that customers request. Meanwhile, testing has become more complex and conventional testing methods cannot keep up with the speed that the market demands. Quality engineering concepts were therefore introduced, and testing time was reduced by one third.