Optimal process adjustment with considering variable costs for uni-variate and multi-variate production process

This paper investigates a single-stage and two-stage production systems where specification limits are designed for inspection. when quality characteristics fall below a lower specification limit (lsl) or above an upper specification limit (usl), a decision is made to scrap or rework the item. the purpose is to determine the optimum mean for a process based on rework or scrap costs. in contrast to previous studies, costs are not assumed to be constant. in addition, this paper provides a markovian model for multivariate normal process. numerical examples are performed to illustrate the application of the proposed method.