Integrated optimisation models and strategies for the improvement of the Six Sigma process

The Six Sigma process typically has the following six phases: Define (D), Measure (M), Analyse (A), Improve (I), Control (C), and Technology Transfer (T), and it is denoted by (D)MAIC(T) process. First, we introduce the steps for each phase of the six-phase process. In order to improve the Six Sigma process, some integrated optimisation models are developed for the analysis and the improvement phases. An optimisation model based on the total cost to the producer and the consumer is given to develop the specifications for the analysis phase. For the improvement phase, three topics are presented: the System Transfer Function (STF), the Variance Transmission Equation (VTE), and an integrated optimisation model to develop the means and variances of the controllable factors of the process, based on the STF and VTE. These topics are also important in terms of the basic research in engineering statistics and optimisation.