The development of environment-conscious soldering technology for mounting resistor units in vehicle components has become mandatory. This report describes a basic research study aimed at optimization of bonding conditions of Pb-free solders and automation of manufacturing processes. The main purposes were (1) to optimize soldering conditions in a manufacturing process and change from manual soldering to robot soldering, and (2) to confirm the usefulness of functional evaluation and demonstrate that the current practice of visual inspection is not reliable enough for evaluating soldering. As a result of experiments and parameter design studies in which generic functions and noise factors were fully examined, guidelines toward the automation of the manufacturing process were obtained. Moreover, visual inspection, which is in general use in the industry, was shown to be inadequate for evaluating the performance of soldering technology, as it cannot evaluate the internal state of the solder,which demonstrates the importance of functional evaluation.

This study concems optimization of multicavity injection molding, in which melted resin is filled into each cavity through multiple flow runners that ramify in the mold. Over-filling and under-filling tend to occur due to differences in filling conditions caused by differences in runner length for each cavity, leading to such problems as defective appearance and failure to achieve the intended dimensions. To establish this difficult multicavity injection molding technology,one-by-one problem solving was considered to be limited and inefficient, so this time we utilized quality engineering, which provides more efficient evaluation. Experiments were performed by simulation to analyze the resin flow, and the flow runners were optimized so as to stabilize the filling of each cavity. The improvement achieved in simulation was confirmed by actual injection molding. In the end we succeeded in improving filling conditions and reducing the amount of discarded resin at the same time.

Paper helicopters are used as tools for teaching robust design in quality engineering,but they are considered to be inadequate as educational tools for teaching robust design to novices lacking quality-engineering experience. In this study, simulation was applied to the robust design of a paper helicopter and a basic model of the paper helicopter was constructed. The basic model constructed is useful for analyzing motions of the paper helicopter, and enables quality-engineering novices to learn robust design easily through motion analysis.

This paper reports a study to optimize a structure of piezoelectric actuated diaphragm by using non-linear FEM (Finite Elements Method). We have conducted the research on the piezoelectric actuators in our products. A compounded noise factor was used, which resulted in a good reproducibility of conclusions. An external pressure, users' environmental noise, was adopted because we suppose that the piezoelectric actuated device is used in harsh environment. This noise was effective and helpful. A gain of 12 decibels on S/N ratio was accomplished; standard deviation has decreased one fourth. Also a gain of 13 decibels on sensitivity was accomplished, β has increased four times. We understood that it became possible to vary sensitivity by 6 decibels without affecting S/N ratio.