Research On Geometric Error Modeling And Thermal Error Compensation Of CNC Worm Gear Machining Machine

The worm gear machine tool is used to manufacture the worm gear which is a basic transmission.The life span and performance of the gear machine tool,indexing turntable and other equipment are greatly influenced by the caauracy of the worm gear machine tool.So it is necessary to find ways to improve the mancfaturing accuracy of the machine tool.The worm gear machining accuracy is affected by the geometric error of machine tool,the thermal deformation error,the force deformation error,the tool error and so on.Among these errors,the geometric error and the thermal error account for the largest proportion.Moreover,if the mapping rule between the temperature field variation and deformation of worm gear machine tool can be figured out,the thermal deformation error can be characterized in the form of machine tool geometric error,and it can be regard as a special form of geometric error compensation research to improve the machining accuracy.Therefore,the modeling and compensation of geometric errors and thermal errors of CNC worm gear machining machine tools are studied as follows.(1)Establish the geometric error model of CNC worm gear machining machine tool.Firstly,the structure of the worm gear machine tool is analysis.On this basis,the geometric error analysis of straight axis and rotating pair is carried out,and the error categories of each axis are summarized.Then,the additional rotation of the workpiece axis is analyzed when the worm gear hob is machining the oblique tooth surface,and the linkage parameters of the hob and the workpiece are calculated.Finally,based on the kinematics of multi-body system theory,the homogeneous coordinate transformation matrixes of the machine tool's transformation chain are derived under ideal state and actual state.The mapping model between the machine tool geometric error and the space error of the hob is established,and fifty-one geometric errors of the machine tool are converted to the space posture error of the hob.The above results provide theoretical support for the sensitivity analysis of machine tool geometric errors.(2)The sensitivity analysis of geometric error of CNC worm gear machining machine tool is carried out.Firstly,the involute equation of the hob was derived.Based on the two-parameter enveloping principle,the contact meshing conditions of the worm gear tooth surface is established.By solving the meshing condition equation,the coordinates of the contact points are obtained,and the mapping model of the worm gear machine tool is established too.Then based on the above model,the Morris analysis method is used to carry out sensitivity analysis on the machine tool geometric errors,and key error terms and sensitive components were identified.The sensitivity analysis based on the mapping model between the machine tool geometric error and the space error of the hob is conducted too.By comparing these two analysis results,the reliability of the former analysis is verified.Finally,the key error terms of tooth surface error are corrected,and the reduction of each tooth surface error term is obtained by simulation.The validity of sensitivity analysis results is verified.The above results provide a theoretical basis for error compensation and precision enhancement of machine tool motion axis.(3)Research on modeling and compensation of thermal error of CNC worm gear machine tool.Firstly,a temperature-thermal deformation acquisition system is designed.Based on this system,the thermal characteristics acquisition experiment of worm gear machining machine is carried out.The experimental data are optimized by clustering,and typical temperature variables are selected as the input of the prediction model to improve the calculation efficiency and accuracy.Then,based on the generalized regression neural network,the worm gear machine tool thermal error prediction model is established.To enhance the prediction performance,the smooth factor which is the key parameter of the neural network optimization is optimized by using the improved gray wolf optimization algorithm.The experimental data obtained in the thermal characteristics acquisition experiment are used to train the prediction mode.By comparing the prediction accuracy and generalization performance with the existing prediction algorithms,the validity of the thermal error prediction model proposed in this paper is verified.Finally,the error compensation experiment is carried out for the WG3125 CNC worm gear machine tool based on its domestic Huazhong HNC-8 numerical control system.The compensation results show that the prediction compensation model can effectively realize the error compensation for worm gear machine tool.