Polymerization methods are replacing conventional pulverization methods in the manufacture of toner for electrophotographic systems, because demands for higher picture quality and color quality have created a need for smaller particles. Many functions are required of a toner. Among them, control of the toner shape is important as it affects adhesion to the photosensitive material and transfer to paper. Toner shape is evaluated by image analysis. A study of the most stable measurement conditions was made. The conditions were optimized through an L₁₈ experiment, which succeeded in finding measurement conditions that raised the precision of the current measurement system.

Due to the rise in concern for the environment, much attention has been focused on illuminant material as a source of clean energy. Illuminant material is economically eflicient, has no running costs, and emits no pollutants such as carbon dioxide and nitrogen oxide. Used daily, it can replace natural sunlight and fluorescent lighting. It can be used in the nighttime for buildings or on the side of ships to identify dangerous items in the water. Illuminants can also be used as emergency lighting in situations such as earthquakes, typhoons and other disaster areas. However, the cost of the raw material necessary to make the molded piece is rather expensive. So, when creating the blend of ingredients,there is a need to minimize the cost, while maximizing the duration of stable light emissions. The purpose of this research is to find the ideal balance between cost and efficiency. Using the L₁₈ table, we identified molding conditions superior to those in current usage. Furthermore, estimation time for the initial light brightness and luminous decay was shortened.

Some switches and other automotive parts are made by welding together two separately molded parts. To reduce lead time and work-in-process, a method of welding the two parts together in the die was developed. In the development of this new method, plastic-to-plastic adhesion was evaluated with the objective of optimizing the molding conditions so as to obtain stronger adhesion. With reference to metal-to-metal adhesion evaluation methods, an attempt was made to evaluate plastic-to-plastic adhesion by a standardized S/N analysis of the force-stroke characteristic of the welded parts, but reproducible gain was not obtained even after repeated analysis of waveform data using several different patterns. A second attempt was then made, using a Cartesian product of an orthogonal array to which the molding conditions were allocated and an orthogonal array to which the data extraction conditions were allocated. As a result, a data extraction method with high objectivity and reproducibility was obtained,enabling an optimal method of evaluating the adhesion of the plastic parts to be found.

Optimization by simulation is still an important issue in quality engineering. This study was carried out to follow the process of optimization by simulation by using the optimization of a clamp mechanism as an example. The process from parameter design to tolerance design was analyzed. As a result, it was shown that iterative optimization improves reproducibility of the gain, and loss is reduced through the process from parameter design to tolerance design.

Parameter design was applied to the design of a disposable intravascular catheter with safety mechanism. Disposable intravascular catheters, like disposable medical devices in general, must combine multiple functions into a simple structure. In the design of this product, the problem was to determine parameters that would simultaneously stabilize three functions having different characteristics. The key point was the selection of optimal factor levels from the factorial effect diagrams obtained for each function by experiments. As this was a high risk medical device, the quality of all functions was equally important. To evaluate each function on an equal basis, functionality was evaluated with noise levels exceeding the anticipated range. The factorial effect diagrams of the functions were then combined to obtain the optimal conditions. It was confirmed that functionality of each function under the optimal conditions was stable,and the design of a safe intravascular catheter was completed using these conditions.

In a measurement system consisting of a commercial scanner and an in-house analysis program, JIS Z 9090 (Measurement-General rules for calibration system) was applied to calculate usage uncertainty, calibration uncertainty, and standard reading uncertainty and obtain a combined standard uncertainty. On the basis of the results, the current calibration system was validated by comparing its calibration interval and adjustment limits with the optimal calibration interval and adjustment limits. In this system, a 0.2-mm thick PET sheet is used as a standard. It was found that the standard reading uncertainty was too high to be ignored. It was also found that in the measurement of diagonal lines, usage uncertainty was high enough to raise problems. The cause was found to be the large effect of the angle at which the sample was placed on the platen, which is an error factor. Countermeasures are lacking at present.