“…The studies by Yang et al (2008) , Lee & Kim (2017) , Cui, Lu, Zhou, & Han (2016 , Xing, Qiao, & Lu (2019) , Feng, Tan, Xia, Pan, & Xi (2019 , Yu & Seif (2016) and Jung, Woo, Koh, & Kim (2018) consider scheduling maintenance before reaching a certain machine age. In Yang et al (2008) , maintenance is performed before reaching a limit on the consecutive number of produced jobs.…”