Reliability degradation monitoring of CNC machine tools based on the SPC method with the Metropolis-Hastings algorithm

After the random failure period, CNC machine tools will enter the wear-out failure period as a result of abrasion, fatigue and aging. Therefore, it is extremely important to monitor the changing trend of operation state and thus to construct rational maintenance policy or determine when to scrap it. In this paper, the mean time between failures (MTBF) is chosen to be the characteristic variable of reliability degradation and is estimated from a Weibull process model. A statistical process control (SPC) chart is then developed using the Metropolis-Hastings (MH) algorithm for condition monitoring. The availability and sensitivity of the proposed method are illustrated through analyzing the field data of a CNC machining center.