Currently, spot welding must satisfy requirements not only on weld strength but also on dust control. A study made last year succeeded in using energy evaluation to calculate welding coriditions that were robust under different machining conditions. The present study extends this functionality (energy evaluation) to the optimization of peripheral devices. Repetitive welding degrades the end of a spot weld electrode, lowering the energy supplied through the end to the base material. The end is therefore periodically recut and renewed with a chip cutter, but this process is not entirely beneficial: the dimensional accuracy target tends not to be obtained, resulting in variations in weld quality. Parameter design was therefore enlisted to optimize the electrode cutting conditions,and two orthogonal array experiments were conducted, from which a high gain and reproducibility were obtained. A feature of this study is that the results were evaluated not from the power consumed by the cutter motor, but by carrying out the welding process using the renewed electrodes, and evaluating the change in cumulative energy supplied to the material being welded.

Our company produces die cast magnesium automobile parts by using a hot chamber plug-shot injection method. As the size of the plug generated at the end of the nozzle increases, injection variability increases, which affects product quality. Various experiments have been conducted on the working casting machine in efforts to mitigate this problem. In this study, the temperature distribution of the nozzle was analyzed and optimized by simulation. The length of the solidified plug was inferred from the temperature distribution of the nozzle and used in a smaller-is-better analysis, with the length as a characteristic value. This led to improved reproducibility and fewer defects, as confirmed on the working machine. The temperature gradient at the center of the nozzle was also analyzed, using the standard signal-to-noise ratio, and compared with the smaller-is-better analysis.

Among the various types of liver disease, autoimmune liver disease is often difficult to diagnose, and as a refractory disease, it is also difficult to treat. The reasons are the many types of overlapping data produced from liver histological findings, blood test results, and the like. Even the results of a liver biopsy sometimes fail to yield a diagnosis. The authors therefore used the Mahalallobis-Taguchi adjoint (MTA) method, which is one technique in the Mahalanobis-Taguchi (MT) system, to diagnose and distinguish autoimmune liver disease. This enabled several types of pathological conditions to be evaluated quantitatively, as reported herein.

Reducing the power consumption of motors has been a recent research topic for motor manufacturers. The power tool industry is no exception; research in this field is aimed at smaller size, higher output, and higher efficiency. Although it depends on the type of motor, much of the loss that occurs in a motor is copper loss. To reduce copper loss, it is important to cool the motor efficiently. The goal of the present study was to optimize the shape of a motor-cooling fan. Improvement in energy efficiency was used as the basic function, and the pressure loss coefficient, which varies from product to product, was used as a noise factor. A fan shape with high energy efficiency was obtained. The final fan shape was used in an actual product to confirm its effect on quality characteristics. The results were a 4-db noise improvement, a 9-degree temperature improvement, and a 1% efficiency improvement.

Reducing aberration is a key point in improving the recording density of optical disks and stabilizing their recording and reproducing characteristics. To reduce aberration, the technological development approach of quality engineering was introduced, and from basic functional considerations, the adhesive used in optical heads was selected as a theme. Development of an adhesive based on the functional evaluation of shape fidelity and curability enabled a pioneering improvement project to be carried out at low cost, and succeeded in reducing aberration variation by about half.

A major problem in the deployment of quality engineering is its strong tendency to depend on human factors. Our firm began with a policy of letting those who wanted to practice quality engineering do so, with the aim of creating a best practice. It was hoped that the creation of best practices would increase the number of advocates and gain the approval of top management, but with this approach, which relies on individual will, there is a high risk that activities will eventually stagnate or stop. A shift to the promotion of systematic and strategic activities that would have a direct business impact was therefore tried out. As a method of maintaining the genes to keep activities going regardless of changes in personnel, a double-barreled approach was used, combining both top-down and bottom-up activities and setting both project themes and specialist themes. As a method of pursuing and evolving both types of activities in parallel, this paper proposes the utilization of a five-stage evolution chart.