Simulation Research On Thermal Variation Effect Of Linear Error Of Linear Feed System Of Precision Machine Tool

For precision machine tools,the thermal error caused by thermal effect is the main factor affecting the accuracy stability.The linear error of linear feed system is an important index to evaluate the comprehensive accuracy of machine tools.The variation caused by thermal effect will have a significant impact on the accuracy stability of machine tools.In this paper,the linear feed system of precision machine tools is taken as the research object.Based on the finite element analysis of thermal characteristics,a modeling method of linear error thermal variation effect of linear feed system based on load optimization correction is proposed.The influence of machine operating conditions and structural design factors on the temperature change,thermal deformation degree and linear error thermal change of linear feed system of precision machine tools is analyzed The theoretical basis is provided for the optimization design of thermal balance of machine tool structure.The main research contents are as follows:First of all,considering the comprehensive factors such as heat generation of internal heat source,heat dissipation of air and circulating liquid in the linear feed system,the finite element simulation modeling method of temperature characteristics of the linear feed system is described.Based on the theory of heat transfer,a theoretical analytical model of generating and radiating load of the feed system is established.The error between the temperature simulation results and the experimental data is taken as the objective function,and a method of optimizing and modifying the thermal load based on genetic algorithm is proposed,so as to improve the accuracy of the temperature characteristic analysis model of the linear feed system by modifying the thermal load required by the simulation model.At the same time,based on the thermal structure coupling analysis,a method of building the simulation model of the thermal deformation characteristics of the linear feed system is introduced.The results of the thermal deformation of the feed system under various working conditions can be obtained by using this method.Secondly,based on the analysis of the mechanism of the linear error thermal variation effect of the feed system,a modeling method of the linear error thermal variation effect of the feed system is proposed.This method can transform the thermal deformation result of the end of the linear feed system under the comprehensive action of each component into the thermal variation of straightness error and positioning error,providing theoretical basis for the optimal design of the thermal balance of the linear feed system.Thirdly,based on the proposed simulation method of the thermal characteristics of the feed system and the modeling method of the linear error thermal variation effect,taking the z-axis feed system of a precision horizontal machining center as an example,the temperature characteristics,thermal deformation characteristics and the linear error thermal changes of the linear feed system under various working conditions such as different feed speed,different coolant temperature and different coolant flow rate are analyzed,and the law of temperature characteristics,thermal deformation characteristics and linear error thermal variation of the feed system are obtained.What's more,the research focuses on the contribution of bed and other large structures to the thermal error effect of the linear error of the feed system,and proposes the optimization of the thermal characteristics of the feed system structure.Finally,the thermal characteristics and thermal error test experiments of the linear feed system are designed and carried out.Simulation modeling method of thermal characteristics of linear feed system and modeling method of thermal variation of linear error is verified by comparing the simulated temperature data of each part of the feed system,the thermal increment of positioning error,the thermal increment of straightness error value and the thermal drift of straightness error test reference line with the experimental results under the same working conditions And the accuracy of linear error thermal analysis modeling method.