Static And Dynamic Characteristics Analysis And Structure Optimization Of CNC Gear Grinding Machine

CNC gear grinding machine is the key equipment of modern advanced manufacturing,and it is also a precision high-grade CNC machine tool.Domestic precision CNC gear grinding machine mainly relies on imports at present,which not only means the higher price,but also the technology is difficult to break through.There are many kinds of joints in machine tool,and their shapes are complex.Which make it difficult to calculate the rigidity of the whole machine,to accurately evaluate the static and dynamic performance,and to optimize the structure.In order to solve the above problems,this work takes L300 G multifunctional CNC gear grinding machine as the research object.By studying the stiffness of the machine tool's key joints,a whole machine finite element analysis model based on joints is established.Analyzing its static and dynamic characteristics and finding out the weak parts of the machine tool and optimizing the design of its structure to improve the comprehensive performance of the machine tool.The full text work is mainly divided into following aspects:(1)A stiffness model of machine tool's joint was established.Analyzing and modeling the key joints of gear grinding machine,such as bolted joints,linear roller guide joints,ball screw joints,and bearing joints.The stiffness of the screw and member for the bolted joints were calculated.Based on Hertz contact theory,the joints stiffness of roller linear guide,ball screw and rolling bearing was calculated,and corresponding calculations were carried out to provide a basis for the accurate establishment of the subsequent finite element models.(2)Analysis of static and dynamic characteristics of gear grinding machine.The finite element model of the whole machine based on the stiffness parameters of the joints was established,and the static and dynamic analysis was carried out.Obtained the displacement,stress and calculated static stiffness of the whole machine under different working conditions in static analysis;And obtained the modal shape,low-order natural frequency and harmonic response parameters under different working conditions in dynamic analysis.Based on the above analysis results,found out the weak part of the bed,and provided a target for subsequent optimization.(3)Design of bed unit structure based on Analytic Hierarchy Process(AHP)and Grey Relation Analysis(GRA).The original unit structure of the bed was extended by the unit structure method,and its static and dynamic characteristics were analyzed to obtain the displacement,stress and low-order natural frequency of the unit structures.The analytic hierarchy process and gray correlation method were used to select the unit structures,and the results of the optimal scheme were consistent.A new bed model was established according to the optimal unit structure,and a static and dynamic comparison analysis was carried out with the original bed structure.(4)Static and dynamic performances optimization of bed structure based on response surface method.After the structural configuration was optimized,the size needed to accurately optimize.The response surface model of the target response of the bed structure with respect to the design variables was established through orthogonal experiment,and the fit analysis and prediction test were performed on it.Each objective function was weighed to establish a comprehensive objective function,the optimal design parameters were solved by genetic algorithm,and the static and dynamic comparison analysis of the bed model before and after optimization was carried out.The results showed that the maximum displacement and maximum stress value of optimized bed structure were reduced by 7.13% and 5.28%,the low-order natural frequencies are increased compared with the original model respectively,and the stiffness and seismic performance of the structure were improved.