A Basic Study on Integration of Process Control and Inventory Control

Abstract

Under the assumption that any process-failure mechanism follows an exponential model, have been studied the economic design of X^^-control charts and the determination of the sampling intervals for process control in many literatures. Recently, when the demand and production rates are given, how to determine the optimal production cycle and the economic production quantity has also been studied, so as to minimize the expected total cost per unit time including the set-up cost and the holding cost. In this paper, we propose a new integrated model of the process control and the inventory control. Concretely, under the assumption that the process-failure mechanism follows a Weibull distribution having an increasing failure rate, how to jointly determine the optimal X^^--control chart, sampling (inspection) interval, production cycle time and economic production quantity is discussed, so as to minimize the total expected cost per unit time including the process control cost, the set-up cost and the holding cost. Furthermore, the following two cases are compared and argued. One is where the process is kept running, and the other where the process is stopped, while searching for a possible assignable cause when the X^^--control chart shows an out-of-control state.