Characteristic Analysis And Thermal Error Modeling For Large Gantry Milling-boring Machining Center

With the rapid development of machine tools to higher speed.more accuracy,and more flexible automation,the higher requirements are demanded to machining accuracy and robustness.Compared with ordinary machine tools,CNC machine tools have more accuracy,and more flexible automation.The higher requirements are demanded to the mechanical properties of the machine tools,such as stiffness,vibration damping thermal deformation and SO on.Therefore,it's important to analyse the static and dynamic and thermal properties of the machinc tools in the design process of the CNC machine tools The certain type gantry milling-boring machine center is taken for the study.The finite element method is used to analyze the static and dynamic and thermal properties of the machine center.Based on the temperature optimization.the thermal error model is established,which lays the foundation for the thermal error compensation.The main contents of the dissertation are as follows:Firstly,static and dynamic characteristics of the beam are analyzed,and the beam structure is optimized and improved.Then,the analysis of static and dynamic characteristics of the whole machine is implemented.Combined with the analysis results.several improved schemes are proposed,which give detailed basis for subsequent mechanical structure optimization of the machine tools.Secondly,according to the basic theory of heat transfer,the thermal loads and boundary conditions of milling-boring machining center are obtained by analyzing of heat situation of each heat source.After that.ANSYS Workbench is employed to analyze the steady temperature field of machining center.According to the steady-state temperature distribution of the machine.its thermal deformation is analyzed and calculated,which ofFers the detailed theoretical basis for the subsequent temperature measuring points optimization and thermal error compensation.Thirdly,a new method combining mutual information and improved fuzzy clustering is presented to optimize the thermal key points of the milling-boring machining center.The optimal number of taxonomic groups is obtained by the improved fuzzy clustering,after that,the thermal key points are determined with comprehensive correlative matrix by combining the temperature variables clustered based on the improved fuzzy clustering method and complex coeff-icient.After that,the multiple linear regression method is used to establish a thermal error prediction model for Y axis linear feed system of the machining center.Based on the thermal error prediction model of the machining center,the implementation process of its Y axis linear thermal error compensation is discussed briefly.