Analysis And Optimization Of Static And Dynamic Characteristics Of The Multi-functional Composite Machine Tool

As a kind of high-end CNC machine tool,multi-functional composite machine tool has been widely used in manufacturing with its unique advantages and has become one of the core equipment of modern manufacturing industry.With the development of multi-functional composite technology towards the direction of high speed,high precision,and high stability,the static and dynamic performance of machine tools are expected to be better and better.Therefore,the analysis and optimization of the static and dynamic characteristics of multi-functional composite machine tools have become an indispensable part of the modern machine tool virtual machine design.In this paper,theoretical model analysis,finite element simulation,structural optimization design and other methods are adopted to study the static and dynamic characteristics of the self-developed multi-functional composite machine tool.Finally,the static and dynamic characteristics of the whole machine are improved by searching for weak parts and optimizing their structures.The main research is as follows:(1)The structure model of the multi-functional composite machine tool was established to calculate the loads of the machine tool under three working conditions of turning,milling and hobbing.the static simulation analysis of the model was carried out to compare the stress and strain of the machine tool under various working conditions,so as to provide a reference for the identification and optimization of the static weak links of the machine tool.(2)Based on the theory of the dynamic analysis on generalized manufacturing space,in view of the characteristics of multi-axis linkage and various working conditions of the machine tool,the modal and harmonic response analysis of the machine tool under the reference pose is carried out at first.Then,the variation of modal information in the process of each axis motion is simulated to obtain the influence law of the structural coupling effect on the dynamic characteristics,so as to judge the key parts that affects the dynamic characteristics of the machine tool's structural coupling and provide a reference for identification and optimization of the dynamic weak parts of the machine tool.(3)Multi-objective size optimization is carried out for dynamic and static weak parts(column-headstock system).an optimization approach combining BP neuralnetwork model with NSGA-? algorithm(non-dominated sorting genetic algorithm-?)was proposed to improving the first two natural frequencies and reducing the maximum deformation by taking the key dimension parameters as design variable,and taking the mass as the constrain.The results show that after optimization,the deformation of the column-headstock system in the limit working condition is decreased by 4.5%,and the resonance peaks of the machine tool in the X,Y and Z directions are decreased by 40.84%,38.33% and 31.90%,respectively.(4)Multi-objective topology optimization based on compromise programming method is carried out for the dynamic weak parts and the easy lightweight parts(the bed structure).Topological optimization is carried out by taking the minimum flexibility of the bed under multiple working conditions and the maximum natural frequency of the low order as the objective,and taking the unit density as the design variable,and taking the volume fraction ratio as the constraint.The results show that after optimization,the mass of the bed is decreased by 9.58%,and the resonance peaks of the machine tool in X,Y and Z directions are decreased by 35.21%,46.67%and 41.38%,respectively.