Prediction Method Of Machining Precision Of CNC Cutting Machine Based On Cutting Force Model

The rapid development of high-end equipment manufacturing industry has put forward higher requirements on the machining Precision of CNC machine tools.In the design stage of CNC machine tools,the prediction of machining Precision is an important means to ensure the reliability of machine tools.When establishing the machining Precision prediction model,the traditional modeling method generally used the form of single system independent modeling.This design method not only can't guarantee the reliability of the machine tool,but also does not consider the coupling factors between the subsystems.In this paper,an integrated modeling method is used to establish a machining Precision prediction model under the coupling of multiple machine tools.Based on the prediction model,the relationship is analyzed between system parameters and machining errors.The specific research contents of this article are as follows:First of all,the finite element model of the infrastructure of the machine tool was established using ANSYS,and the number of degrees of freedom of the finite element model was reduced by the modal order reduction method.The system matrix and loworder transformation matrix of the model have high dimensions and complex calculations.The finite element model of the machine tool is used to obtain the frequency response function of the system.The transfer function matrix is identified by extracting the natural mode of the frequency response function at the specified coordinates.The state space equations of Machine tool basic parts are established in MATLAB/Simulink.Then,the parametric equations of the servo system are established by using the lumped mass method,and the electromechanical coupling parameter equations of the servo system are transformed into state space equations by the state space method to better describe the internal variables of the electromechanical coupling system and the input/output relationship.Later,the state space equations of the Machine tool basic parts were coupled with the state space equations of the servo system to establish a machine tool dynamic model,and the reliability of the modal reduction model was verified by simulation.Secondly,in view of the coupling effect of the spindle-tool system during the cutting process,a microelement cutting force model was established;the effects of tool runout,structural vibration,and feed-driven vibration during the milling process were considered,and a theoretical model of instantaneous undeformed chip thickness was established based on the linear relationship between the cutting force of the micro element and the instantaneous undeformed chip thickness,the instantaneous cutting force model of the cylindrical milling cutter is established;due to the offset problem after the tool is mounted on the spindle,the eccentricity model of the spindle-tool system is established;Finally,the influence of cutting force under multi-frequency excitation was analyzed based on the cutting force dynamics model.Then,the integrated modeling method was used to build the simulation model of the machine tool dynamic model,cutting force model and spindle-tool system model according to the actual combination relationship of the CNC machine tool in Simulink,and the evaluation index of the simulation system was determined.The instrument tested the response of the machine tool,and compared with the simulation results to verify the rationality of the response characteristics of the integrated prediction model.Finally,the accuracy of the integrated prediction model of machining precision under multi-system coupling conditions was verified through the round table workpiece cutting experiment.Based on the integrated prediction model,the relationship between different cutting conditions such as control gain,feed rate,spindle speed,axial cutting depth and the cutting error of the circular workpiece was analyzed.