The Structure Optimization Of Five-axis High-speed Gantry Machining Center Based On Stiffness Matching

With the development of modern industry,the performance of machine tools is required to be higher and higher.In traditional machine tool design optimization methods,designers generally use the method of sensitivity analysis to optimize the machine tool to improve the static and dynamic performance of the machine tool.The large-size five-axis gantry machining center has large parts and large quality.The stiffness matching between each part has a significant impact on the static and dynamic performance of the machine.This paper proposes a method to optimize the static and dynamic characteristics of the whole machine by matching the stiffness of the main components of the machining center.The main contents are as follows:(1)Taking a gantry machining center as the research object,the finite element model of the whole machining center is established.Modal tests were carried out on the beam,saddle and ram components of the machining center to verify the accuracy of the finite element model;the dynamic cutting force of the machining center is measured by Kistler test system,and the component forces in the X,Y and Z directions of the machining center tip are obtained.The measured cutting force is used as the load to carry out the static analysis of the machining center;the static analysis results show that the static stiffness of machining center in X direction is the weakest,and the sensitivity analysis of machining center tip deformation is carried out with the component stiffness as the design variable.The analysis results show that the ram component has the greatest impact on the static stiffness of the whole machine in X and Y direction,and the beam component has the greatest impact on the static stiffness of the whole machine in Z direction;Analyze the static deformation and displacement nephogram of the ram and beam components,and judge the weak position of the rigidity of the ram and beam components.(2)The modal analysis and harmonic response analysis of the gantry machining center are carried out to obtain the low-order natural frequency of the gantry machining center and the dynamic characteristic parameters such as the maximum amplitude of the harmonic response in the X,Y,and Z directions,which provides a design basis for the design of the component stiffness matching..(3)Using the optimal Latin hypercube test design method,multiple sets of component stiffness sample points are drawn twice,and the first-order natural frequency of the gantry machining center corresponding to each group of sample points and the maximum amplitude of X,Y,and Z harmonic response are calculated;The response surface(RSM)model,radial basis function(RBF)neural network model and Kriging model between the first natural frequency of the whole machine and the maximum amplitude of harmonic response in X,y and Z directions and the component stiffness are established respectively by using the first sample data;Using the sample points extracted for the second time to compare the model accuracy of the three agent models,it is found that the radial basis(RBF)neural network model has the highest fitting accuracy.The agent model is finally selected as the radial basis(RBF)neural network model.(4)Based on the first-order natural frequency of the gantry machining center and the maximum amplitude of the harmonic response in the X,Y,and Z directions and the radial basis(RBF)neural network model between the rigidity of the main components of the machining center The optimal solution is obtained to obtain the optimal distribution scheme of the stiffness of the machining center components.Under the optimal stiffness distribution scheme,the first natural frequency of the whole machine is increased by 2.99%.10.The maximum amplitude of harmonic response in Y and Z directions decreased by 4.42%,8.67% and 1.43% respectively.According to the rigidity matching scheme of machining center,the ram components are selected for structural reconstruction,and the new RAM is obtained by topology optimization.The finite element calculation model of the new RAM is adopted,and the static and dynamic performance of the whole machine are effectively improved.