Research On Thermal Characteristics Modeling And Structural Optimization Of Precision CNC Worm Gear Grinding Machine

The precision CNC worm gear grinding machine,as the machining "master" of precision gear processing and manufacturing,has a strategic significance for the industrialization level of a country.At present,the geometric accuracy of domestic CNC worm grinding machines has been relatively high,and the thermal-induced error has become a major factor that restricts the machining accuracy of CNC grinding machines.The mechanisms of thermal error and the of CNC worm grinding machines are widely studied.In the design stage,the optimization of machine tool topology,layout of cooling flow channels,and combined with sensitive temperature control methods are used to achieve the suppression of end machining errors of CNC machine tools;at the same time,the thermal error measurement,modeling and prediction techniques for CNC machine tools are being conducted.Improve machine tool machining accuracy and stability.The main work of the paper is as following.This paper analyzes the heat generation mechanism of the key heat sources inside the gear grinding machine and the heat dissipation mechanism of the workpiece spindle components.Based on the pseudo-static analysis method of angular contact ball bearings,the angular contact ball bearing equilibrium equations including the geometrical equations,the load balance equations of the rolling elements and the inner-outer ring,and the Newton-Raphson algorithm are used to solve the bearing heat generation.The efficiency analysis method solves the heat generation;solves the convective heat transfer coefficient of the gear grinding machine and the contact thermal resistance of the bearing.The thermal boundary conditions such as the heat source power and heat dissipation were applied to the finite element model of the thermal-structure coupling characteristics of the Rotating worktable system to simulate the thermal characteristics of the CNC gear grinding machine in multiple working conditions.By rationally designing the structure,number and arrangement of the ribs of the bed,the symmetrical symmetry distribution of the whole CNC machine tool can be achieved,and the thermal deformation of the work-piece spindle in the radial direction can be effectively reduced and then the machining accuracy of the CNC grinding wheel worm gear grinding machine could be improved.At the same time,the cooling oil pool was designed on the bed to achieve a more even distribution of the temperature field of the bed.Finally,the optimization of the thermal-structure coupling characteristics was realized and the thermal deformation of the CNC worm wheel grinding machine tool was effectively suppressed.The temperature sensor was used to measure the temperature field distribution of the CNC gear grinding machine.The displacement sensor was used to accurately characterize the space position of the work-piece spindle system.The gray grouping method was used to group the temperature measuremeut points,and the key temperature measurement was selected according to the correlation analysis method.point.Based on the support vector machine and the multiple linear regression theory,the thermal error prediction model of the work-piece spindle system is established respectively.The robustness of the thermal error model is verified.The results show that the thermal error based on the support vector machine and multiple linear regression theory proposed in this paper.The model can accurately predict the thermal error of the work-piece spindle system under different operating conditions.The least squares support vector machine model has better robustiess and versatility.It is of great theoretical significance and engineering application value to study the combination technology of thermal characteristic analysis method and thermal error modeling prediction method of the gear grinding machine to realize the manufacture of precision CNC gear grinding machine.