Research On Multi-objective Optimization Integrated Design Method Of Small Precision Machine Tool

With the wide application of complex micro-parts in the field of high technology,small precision machine tool has been required higher machining accuracy.In the stage of machine tool design,the optimization of structural performance is one of the important ways to improve the machining accuracy and surface quality of parts.However,the single performance optimization design such as stiffness,thermal characteristics and accuracy is difficult to ensure the optimal structural performance of the whole machine,and the coupling relationship between various performances is not taken into account,which cannot satisfy the requirements of the development of small precision machine tools to higher precision.Therefore,by analyzing the effect of stiffness,thermal characteristics and precision performance on the five-axis small precision machine tool,this paper studied comprehensive optimization design of each performance by using the integrated design method to guide the whole machine system design scientifically and systematically.In this study,the structural model of five-axis small precision machine tool is built,and the dynamic model of topological structure of machine tool is established based on the transfer matrix method of multi-body system to obtain the natural vibration frequency parameters of the system.At the same time,the substructure model of machine tool is divided by dynamic substructure method based on the dynamic model of topological structure,and the substructure model is verified by finite element method and multi-body transfer matrix method.In addition,the dynamic stiffness characteristics of the position relationship of the substructure are determined,and the matching optimization design of the dynamic stiffness of the substructure and the dynamic stiffness of the whole machine structure is completed as well.Furthermore,aiming to solve the problem of compact structure and slow heat dissipation of the small machine tool,the thermal environment of the machine tool is simulated by numerical method,and the main heat source and boundary conditions of the machine tool are determined by the mechanism of heat transfer and thermal deformation.Then,the temperature field and thermal-structural coupling deformation field models of the whole machine are established by using finite element simulation technology.On this basis,the thermal optimization design model of machine tool is established to guide the thermal characteristics research of small precision machine tool.Then,the topological structure of small precision machine tool is established based on the theory of multi-body system to analyze the geometrical error elements of the machine tool,and the spatial error model of the whole machine is built.The key geometric error elements affecting the spatial error model are identified by sensitivity analysis.Meanwhile,the accuracy distribution criterion of the machine tool is determined by the percentage of the sensitivity coefficient of each geometric error element to the total sensitivity coefficient of the geometric error element,which provides a theoretical basis for precision design of small precision machine tools.Finally,an integrated mathematical model of machine tool stiffness,thermal characteristics and precision is built.The model is based on the study of the stiffness,thermal characteristics and precision performance of small precision machine tool,and the design objective is to optimize the structural performance of the whole machine tools.In addition,the multi-objective optimization integrated design method is presented with the i SIGHT optimization design platform to carry on the integrated research on the comprehensive performance,and the study for multi-objective optimization integrated design of the five-axis small precision machine tool is complete.