Selection of characteristic values with good additivity is considered important for ensuring reproducibility in parameter design. Functional evaluation by the S/N ratio is recognized as an effective selection means. For tolerance design,however, in which factor levels may have to be set within a narrow range, interaction effects have rarely been discussed. In tolerance design in fields with strong intrinsic interactions, such as optical design, reproducible effects have not been obtained and analysis by use of orthogonal arrays has not been possible in practice. To solve this problem, a new direct productt tolerance design method was developed. When used in actual optical design, it avoided interaction effects and gave results with good reproducibility. This showed that using the S/N ratio as a characteristic value is an effective way to ensure reproducibility in tolerance design as well as in parameter design.
Aircraft engine disks are critical rotating parts and flaw detection by non-destructive inspection is essential. Since surface defects in particular can be the origin of fracture, eddy current inspection is carried out. This paper seeks robust inspection conditions that increase the S/N ratio (ratio of the defect signal component to the irregular signal component caused by surface conditions that hamper detection of the defect signal) and examines the analytical methods for setting the conditions. Although the gain was reproduced in a zero point proportional analysis of the defective area and S/N ratio, in the factor effect diagram of the S/N ratio there was considerable ripple and slope in the error column. To remedy this problem, the defect and irregular signals were analyzed independently and the defect signal was analyzed using a reference point proportional expression with a zero-point adjustment made according to the irregular signals component. As a result, detection capability was improved in a direction that reduced the irregular signal component, and under the optimal conditions,it was possible to detect minute flaws that had been difficult to detect with the conventional flaw detection conditions.
Remote monitoring systems are being increasingly used to improve the availability of gas turbine combined cycle (GTCC) plants. The key to improving plant availability is early detection of problems. Round-the-clock monitoring enables quick troubleshooting, and remote monitoring systems play an important role in diagnosis of abnormal symptoms. Remote diagnosis technology has advanced and is helping to prevent major malfunctions by detecting small signs of trouble before the trouble becomes serious. By minimizing damage and unplanned halts, this contributes to the improvement of plant availability. One remote diagnostic technique is the MT method, which has proved to be highly effective in diagnosing anomalies in GTCC plants.
Semi-dry machining is attracting attention as a technology that reduces not only usage of cutting fluid but also the total amount of electric power consumed during cutting work. When the amount of cutting fluid supplied is greatly reduced, however, if proper supply conditions cannot be set, product quality cannot be maintained. Also, as tools are subject to wear, the same machining conditions cannot be expected to last until the end of the life of the tool, but the cutting fluid supply conditions generally cannot be changed during the machining process. Robust design of cutting fluid supply conditions then becomes necessary to accommodate changes in machinillg conditions that accompany progression of tool wear. This paper focuses on robust design by quality engineering methods. A method of determining optimal robust supply conditions from various combinations of cutting fluid supply conditions was studied. Experimental results showed that a higher S/N ratio led to a greater reduction in tool wear, and this tendency continued until the end of the tool life. The method is thought to have found optimal conditions and simultaneously produced a robust design.
Engineering development is a free world and need not be standardized, but there must be standardized methods of measuring and comprehensively evaluating the results of engineering development. Therefore, standardization of quality engineering as an evaluation technology is necessary. For the strategy of standardization, it is important to clearly define the position of standards as viewed from quality engineering and the position of quality engineering as viewed from the standards. To give standardization clear directions, the history of standardization is reviewed and the significance of standardization for quality engineering is set forth together with the requirements for future standardization.