“…Since their degradation and damage level can be affected by working operations as well as other disturbances in harsh manufacturing environments, such as lubricants, soiling, and temperature, the results from traditional wear and fatigue models are connected with considerable uncertainties. DT-driven condition monitoring (CM) and predictive maintenance (PdM) highlight the possibility for the process-parallel monitoring and diagnosis of the health status of the critical components (i.e., tools [ 116 , 117 ], bearings [ 118 ], ball screws [ 119 ], gears [ 15 , 120 , 121 ], pumps [ 122 ]) and the energy efficiency of the equipment [ 123 , 124 ] in order to handle the conflict between the unplanned maintenance operations and the resulting costs and productivity, particularly in SMEs, due to their limited capacity for the full deployment of a PdM strategy [ 125 ]. Additionally, DT-based optimal control [ 126 , 127 ] as well as machine dynamics issues [ 128 , 129 ] from a rotating system [ 130 ] to feed drive [ 131 , 132 ] are other important aspects.…”