Abstract

To address concerns regarding economic risks and reliability issues in existing maintenance practices, this study introduces a novel condition-based maintenance model that considers failure risks in terms of both cost and availability. Utilizing a Markov decision process, this model determines inspection intervals and maintenance policies aimed at minimizing the nested conditional Value-at-Risk of cumulative costs while satisfying operational availability constraints. By applying this model to the plasma etching process, we demonstrate its effectiveness compared with existing maintenance models. Additionally, we found that higher risk levels do not necessarily lead to stricter maintenance policies, whereas achieving better operational availability incurs additional costs. These findings highlight the importance of balancing cost and availability risks when determining an optimal maintenance policy.