An Integrated Model of Eliminating Early Failures for NC Machine Tools: A Case Study

Abstract

A fundamental tenet of reliability theory is that the hazard function during NC machine tool’s life cycle displays a bathtub curve, and the curve can be viewed as comprised of early failure period, random failure period and wear-out period. To eliminate the early failures and improve the reliability of NC machine tools, this paper proposes the model and steps of eliminating early failures for NC machine tool. Firstly, Weibull two-fold mixture model is chosen to establish the bathtub curve model of NC machine tool, and division between early failure period and random failure period is identified. Secondly, the formation of early failure period and mechanism of early failures elimination are studied, and an integrated model of eliminating early failures for NC machine tool is established with reliability design and analysis domain, reliability test domain and early failures elimination domain. Finally, an example of rotary table in NC machine tool is shown to illustrate the applicability and validity of the model.