Digital Twin for NC Machining Using Complete Process Information Expressed by STEP-NC Standard

The concept of Digital Twin has been accepted by more and more researchers and enterprises. Many applications of Digital Twin systems are reported such as airplane state monitor and smart factory. In addition, the digital twin is an important measure to achieve intelligent manufacturing and industry 4.0. The advancement of DT system in manufacturing environment is evident. However, current researches in manufacturing domain concentrated on the discussion of architecture optimization of digital twin system combining with existing cyber-physics researches. There are little research works reported practical DT system and discussed the technologies in implementation. Different from current works, this paper proposed an advanced Digital Twin system for CNC machine tool and discussed the critical enablers to make the DT system more practicality. First, data stream from CAD/CAM to CNC is improved with the STEP-NC standard which containing more structured process data to enhance the information in virtual environment to reflect the real machining process. Second, hardware connection method with CNC system is summarized and a uniform interface for data accessing is proposed to simplify the development of DT system. At last, a virtual machining environment (software named "GrapeSim") is presented which contains three functions: estimating the machining state according to the accessed data from CNC; material removing simulation that synchronous with the real machining process to illustrate the geometry shape of machined workpiece; a web server that allowing other devices to obtain the data in virtual environment as a data source of cloud manufacturing. The whole Digital Twin system is tested in COMAC, the manufacturer of ARJ21 and C919 jetliner, and all functions are proved stable and useful.