| Nowadays,CNC machining technology is developing in the direction of high-speed cutting,high-precision control and high-flexibility.The factors which have little effect on the dynamic characteristics of machine tools under traditional machining conditions may cause the vibration and weaken of the precision in modern CNC machining.The working position of CNC machining center changes over time when the machining process of the workpiece determined.The time-varying characteristics of working space will lead to the rigidity and mass distribution of the CNC machining center whcih will also result in time-varying dynamic characteristics of CNC machining centers.In this paper,time-varying characteristics of the machining position about the CNC machining center and the influence of the movable combination on the dynamic characteristics has been taken into fully consideration.The working space has been subdivided by using discrete method and the typical machining position of its milling and boring system has also been selescted.Dynamic characteristics analysis of the CNC machining center and its dynamic characteristic data has been carried out and extractd by using the interpolation method to fit the working space.Besides,we also establishe its dynamic characteristic spectrum and propose to improve the machining accuracy of the CNC machining center.The main contents of research in this paper are as follows:1)Establish a three-dimensional model of the movable joint surface of the composite boring and milling machining center,and derive the stiffness of the main movable joint ball screw pair and the linear guide pair by Hertz contact theory,and combine the finite element analysis software to the joint surface.The finite element analysis calculates the simulated stiffness of the two based on the post-processing data and compares it with the theoretical value.2)Modeling the milling and boring part of the compound boring and millingmachining center,and analyzing the dynamic and static characteristics by the finite element method,and obtaining the static analysis diagram,modal frequency and mode vibration of the milling and boring parts.The type map provides the basis for harmonic response analysis.3)Through the discretization of the working space of the compound boring and milling machining center,select the typical machining position,and combine the dynamic and static analysis results to analyze the harmonic response of the milling and boring parts,and then re-fit the data after the post-processing to build the CNC machining center.The dynamic characteristics of the workspace are summarized and the rules are summarized.4)Based on the simulation results,the human-machine interaction interface is established for the compound boring and milling machining center.At the same time,the numerical control machining precision optimization of the complex object box parts is discussed.The modal state of the first six-order modal frequency of the box is established.Spectrum,summarizing the law and avoiding resonance.Finally,the lowest point of the tool holder is selected to establish the dynamic characteristic spectrum of the machining position of the CNC machining center,and the optimal machining position is selected to provide suggestions for the optimization of machining accuracy. |
