Study On Simulation And Experiment Of Turn-milling Mechanism And Dynamic Characteristics

With the rapid advancement of scientific technology, high-grade NC machine tools with high speed, high precision, high efficiency, and multi-purpose turn-milling center are the directions in developing modern NC machine tools. NC machine tool with turn-milling function is suitable for machining complicated parts and products that demand short cycle time to improve production efficiency and machining precision. The turn-milling centre satisfies the demand of military projects, since it enables machining of work pieces of different shapes without changing the set-up. Unfortunately, due to the long process in obtaining the final configuration, it costs a lot of investment and time to design and develop a turn-milling centre.With the fast development of information technology, computer modeling and simulation have become the important tools in manufacture development in 21^st century, including a powerful analytical method for turn-milling center. Determining the dynamic characteristic, machining performance using available technology and methods is the primary objective in analyzing turn-milling center. Using theory modeling, simulation and experiment based on computer modeling and simulation technology turn-milling center is characterized in the present paper, which hopes to provide a reference foundation for its structural optimization, control system design and machining feasibility. The research contents are as follows:(1) The research background and the objectives of the current world-wide development of the turn-milling center are discussed. With the help of computer technologies, the high-grade NC machine tool can be modeled analytically and simulated. The purpose of the research and the possible applicatons of the machine tool are also summarized.(2) Turn-milling center is modeled using integration method of virtual prototype and finite element to form a virtual prototype model that is composed of rigid and flexible elements. The kinematics and dynamics simulations of the turn-milling center are analyzed to solve the problems of motor parameter selection and mechanical design. The results with integration method are not only close to the actual condition, but also they provide a reference for the motor selection, structure design and control system design.(3) Firstly, key components of the turn-milling center are analyzed as lumped masses. By modeling springs and damping units as bearing support, the behavior of the bearing stiffness and bearing span affect natural frequency and bearing stiffness and damping affect displacement in harmonic response. Then, the vibration model of turn-milling is developed by integrated method of virtual prototype and finite element to form rigid-flexible coupling system. Nature frequency and displacement response of the whole machine tool are got by excitation simulation based on the vibration model, which provide reference foundation for structure design of turn-milling centre. Finally, exciting simulation results are reliable, because it is valid by experiment modal measure.(4) In order to determine the variable cutting depth and variable cutting thickness in orthogonal turn-milling complex motion, the theorical models of centric and eccentric chip formation are built respectively to get cutting depths and thicknesses in peripheral cutting edge as well as in face edge. The orthogonal turn-milling chip model is verified by comparing the geometric chip formation with the experimental formation.(5) The centric and eccentric cutting forces are simulated using mathematic models, and the regular pattern of cutting force with variable cutting angles are calculated. Three dimensional chatter theory model is built based on turn-milling chatter mechanism, and transfer function and turn-milling stability lobes are determined and validated by experiment providing guidance for machined surface quality and machining efficiency.(6) The mathematic model of surface morphology is built by turn-milling trajectory constructing function. To simulate the effects on the surface morphology and surface roughness is simulated with different machining parameters. Finally, The modeling and simulation methods are proven to be feasible and through the turn-milling surface morphology experiment.