Internal deployment of quality engineering at IHI began in 1994 and has continued up to the present. Despite the passage of some seventeen years, the current level of deployment could not be called adequate. To clarify the issues involved in taking the internal deployment of quality engineering to a higher level at IHI and see how to deal with them, a case study was carried out, using a case in which quality engineering had been applied, to determine whether the principles asserted by Genichi Taguchi were actually being followed. Deviations from Genichi Taguchi's principles were taken as issues confronting internal deployment, and ways of responding to these issues were studied. As a result,two issues became apparent and four root causes and responses were clarified.
Avariety of components are handled in assembly processes performed on production lines, and many of those processes include a number of steps, each requiring quality assurance. Many inspections are therefore carried out, including inspections of semifinished products during the assembly process, inspection of finished products, and pre-shipment inspections. If even a small number of defective products are being passed to the next step or to the customer, production continues but an additional inspection is added to a step in which the defect can be reliably detected. As more and more inspections are added, they tend to overlap: multiple inspections are performed to detect the same type of defect. To reduce such unnecessary overlap, the present study proposes a method of reducing inspection costs and remedy costs by applying the inspection design techniques of online quality engineering not just to individual inspection steps but to the entire production line, comparing repeated inspection losses, noting what is being inspected, and making the inspection processes more efficient through thorough analysis, down to defect type.
A self-rated health score indicates an individual's perception of his or her own state of health. Feeling healthy is important, so self-rated health scores are taken seriously in the medical field, but there are no instruments that can be used explicitly to measure self-rated health. The present study used the MT-system to create a scale based on a database including controllable factors, with which self-rated health was improved. Scores of 5 points out of a maximum of 10 were raised to 7 by an identifiable combination of factorial effects. These findings may contribute to the evolving methods of measuring changes in self-rated health when a person changes his or her own behavioral pattern.
An understanding of the ideas and mathematics of the loss function does not always provide a real sense of its significance. A major factor is the lack of evidence based on follow-up field studies. A survey and study were carried out to verify the loss function through post-shipment quality data. Instead of comparing the quality level calculated by the loss function with the actual monetary loss resulting from defects found after shipment, including defects found during further processing by the customer, different indices were compared. The quality level was replaced by the S/N ratio obtained through evaluation of product functionality, and the monetary loss was replaced by an index based on the number of customer complaints. A comparison of these substitute indices across model groups of switches indicated a strong correlation, demonstrating the validity of the loss function. To determine specific actions to be taken on the basis of the loss function, however, it will be necessary to calculate the total loss by adding the action cost to the monetary loss, instead of using a substitute index. Further study will be necessary.