Research On Key Technologies Of Physical Simulation For Virtual NC Milling

Virtual manufacturing technology is the integration of traditional manufacturing technology and information technology. In recent years it has been rapidly developed and become a focus and advanced subject in manufacturing. The research and development of virtual manufacturing has been attached great importance to countries in the world. Virtual NC machining technology is the core of virtual manufacturing. It has great significance to display NC machine tools's potentiality fully, and improve the efficiency and quality.In this dissertation, the idea of combining theoretical analysis and experimental research is used. Aiming at the characteristics of NC milling, the key technologies of physical simulation for NC milling including milling forces modeling, milling temperature modeling, cutter wear modeling, machining quality prediction, machining error analysis and compensation, machining parameter optimization are researched. The dissertation fastens on the following issues:The overall plan of physical simulation for virtual NC milling is researched. System structure of physical simulation for virtual NC milling is proposed. Process of system simulation and analysis is designed. The simulation database structure and function model is built. Simulation environment of virtual NC milling is built. Data sharing and efficient integration of geometric simulation with physical simulation is realized, by which laid the foundation for physical simulation for virtual NC milling.Physical simulation model of NC milling process is researched. Considering a variety of factors in the actual milling process, the physical simulation model fitted a high degree with actual cutting of milling forces, milling temperature and cutter wear are built based on test. Milling force acting on a cutting edge element of ball-end cutter at arbitrary feed direction is analyzed. Milling forces model of ball-end cutter cutting edge element is established by considering the impact of deformations caused by the milling forces, spindle eccentricity and vibration. Temperature simulation model of ball-end cutter milling is established on the basis of experiment. Mathematical model of temperature field when work piece is milled by ball-end milling cutter is established by using moving heat source theory. Then finite element analysis and dynamic simulation of the temperature field is carried out on the basis of considering the impact of various factors. Tool wear simulation model of ball-end milling is established by using different processing parameters and tool parameters for NC milling experiments, and by using multiple linear regression model to determine the various coefficients of tool wear. The experiment results show that the model is correct.A more comprehensive optimization model of objective function, decision variables and constraints is established. Genetic algorithm is improved for the non-negative, more constraints and more complex objective function of cutting parameters optimization model. An improved parallel multi-objective optimization genetic algorithm selection is established. A multi-objective optimization model of milling parameters selection based on improved genetic algorithm parallel is established. The optimal cutting parameters are obtained based on the simulation results predicted by physical simulation system for virtual NC milling. The machining experiments verify the effect of optimization. The target of machining quality improving, productivity and processing cost savings is achieved.Finally, the prototype system of physical simulation for virtual NC milling is implemented. Operation and implementation process of the system is designed. The integration of simulation and physical simulation in machining process is achieved. Product geometric modeling, virtual machining process simulation, interference, undercutting and less cutting test, milling force simulation, milling temperature prediction, prediction of surface roughness and machining error analysis are achieved in the technology system of XH715 processing center. NC program is adjusted and optimized by machining error compensation and milling parameter optimization. The reliability of the system is verified by analyzing the comparative results of simulation and the actual cutting tests.