Dual-response optimization for lifetime improvement experimental designs

Manufacturing process parameters often affect product reliability significantly. Practitioners need to improve product lifetime and reduce its variance simultaneously by optimizing process parameters. However, an important feature of lifetime distributions is that the variance increases as the mean increases. Practitioners should make a trade-off between them. In this article, we present a dual-response optimization approach to get optimal trade-off of percentile lifetime and lifetime variance. A new criterion is introduced to maximize the product reliability in the warranty period. We illustrate the proposed method via a real example and a simulated example. The optimization results show that the optimal solution is not a constant for different warranty periods. Practitioners should select different important factor levels for different scenarios. Furthermore, we compare the proposed method with other methods. The proposed method performs better than other methods significantly. Additionally, we present some discussions about the determination of significant factor levels.