Monitoring of machining processing of CNC machines This paper discusses in detail the effects of cutting variables, tool geometric parameters, workpiece materials, etc. on cutting force, cutting heat and tool life. Based on the concept of digital twins, a digital twin model of cutting tools oriented to the cutting process is proposed, and the physics is created digitally. The virtual model of the entity uses data to simulate the behavior of the physical entity, promote the interaction and integration of physical world and digital world through virtual and actual interactive feedback, data fusion analysis, and decision-making iteration optimization, and adds or expands new capabilities for the physical entity.