| This research is concerned with the optimization of the quality system for product or process to achieve high quality with low cost. This can be done by minimizing quality loss through both off-line and on-line quality control activities. The most important phase in off-line quality control is robust design, which is a cost-effective methodology to minimize performance sensitivity to noise factors. To achieve this goal, Taguchi originally proposed his optimization strategy by minimizing variance while bringing mean on target. We propose an enhanced optimization strategy within the framework of Response Surface Methodology by simultaneously considering bias and variance and show that the proposed strategy can provide a better solution than the other solutions in the literature. Even after optimum levels of control factors have been chosen through the robust design, noise factors still remain. The production variability due to these noise factors can be reduced by implementing specification limits. The specification limits must be determined by an economical basis of minimizing total cost both to the producer and to the customer. We present optimization models for economic specification limits (region) for single (multiple) quality characteristic(s). These off-line and on-line quality control activities help us meet or exceed customer's requirements, which is the key objective of Quality Engineering. |
