Prognostics and Health Management (PHM) and Cyber-Physical System (CPS) are major technologies in smart factory research. In PHM, the fault diagnosis and remaining useful life (RUL) prediction of several manufacturing systems including the industrial welding robot, 3D printer and CNC machining center have been studied based on appropriate artificial intelligence (AI) algorithms. In addition, CPS development is carried out via a digital twin of the physical mechanical system. For instance, the digital twin of the industrial welding robot has been developed through the kinematic modeling and synchronization between physical and cyber signals.