Dynamic Characteristics Analysis Of Five-axis Machine Tool With Double Turntable Considering Joint Under Milling Conditions

As the basic manufacturing tool of equipment manufacturing industry,five-axis machine tool with double turntable needs to develop towards high manufacturing speed,high machining accuracy and high reliability.There are many component units and interconnected joints in the structure of the five-axis machine tool with double turntable.The joints have complex contact stiffness characteristics.In the actual machining process,when the contact stiffness of the joints changes,the dynamic characteristics of the machine tool will also change.This requires that when analyzing the dynamic characteristics of the machine tool,the milling load existing in the actual machining process and its influence on the contact stiffness of the joint must be considered,so that the analysis results of the dynamic characteristics of the whole machine tool structure can be closer to the actual operating conditions.In this paper,aiming at the change of dynamic characteristics of the five-axis machine tool with double turntable in the process of machining,the dynamic characteristics parameters of the five-axis machine tool with double turntable are obtained by comprehensively considering the contact stiffness characteristics of the joint under different milling loads,as well as the influence of machining station and swing angle.After being verified by an experimental method of dynamic characteristics of five-axis machine tool with double turntable under milling conditions,orthogonal experiments are designed to analyze the sensitivity of factors,and a prediction model is established based on BP neural network to obtain the dynamic characteristics of five-axis machine tool with double turntable under the influence of multiple factors.The main research contents are as follows:In order to make the calculation results of the model more in line with the actual operating conditions of the five-axis machine tool with double turntable,based on Hertz contact theory in elasticity,the mechanical model of milling load-joint,the contact stiffness model of rolling linear guide rail joint and the contact stiffness model of ball screw pair joint are established,and the contact stiffness characteristics of rolling linear guide rail joint and ball screw joint under the influence of milling load are obtained.The contact stiffness characteristic parameters of rolling linear guide rail joint and ball screw joint are substituted into the dynamic model of five-axis machine tool with double turntable.The natural frequency and frequency response characteristics of the machine tool are obtained by using finite element simulation,and the results are compared with those obtained under the static working condition of the machine tool.An experimental method of dynamic characteristics of five-axis machine tool with double turntable under milling conditions is applied,that is,the milling load signal is used as excitation and the vibration acceleration signal of lathe bed is used as response,the harmonic frequency in periodic milling load signal is eliminated by singular spectrum analysis,and the modal parameters of the whole machine are extracted to verify the accuracy of theoretical model calculation results and simulation results.On this basis,by adjusting the machining station,swing angle and contact stiffness of the joint under different milling loads of the five-axis machine tool model with double turntable,the dynamic characteristic parameters are obtained and orthogonal experiments are designed to analyze the sensitivity of different parameters to the dynamic characteristics of the machine tool.Through BP neural network,the dynamic characteristics prediction model of double-turntable five-axis machine tool under milling conditions is established,and the changing trend of dynamic characteristics of double-turntable five-axis machine tool under the coupling influence of processing station and milling load is obtained,which lays a theoretical foundation for accurately predicting the dynamic characteristics of double-turntable five-axis machine tool under milling conditions.