Research On The On-machine Compensation Technology Of Pitch Deviation For The High-precision Large Gear Hobbing

High-precision is an important development trend in the field of large gear processing.As a kind of gear processing machine With the constant pursuit of high-precision machining of large gears,Higher requirements for the accuracy of hobbing.Based on the error compensation technology,the machining error of the CNC gear hobbing machine is compensated,which has gradually become the mainstream method for improvement of machining precision in various countries.At present,most of the hobbing machining error compensation is compensated for the error of the hobbing machine tool.The compensation of geometric error is generally off-line compensation.In this case,the geometric error of the hobbing machine needs to be comprehensively measured beforehand,while the force error and thermal error are dynamic errors,which need real-time monitoring and measurement of the machining process.Whether it is off-line compensation for the geometric error of the hobbing machine,or online compensation for the cutting force and cutting heat of the hobbing machine,there are problems of high cost and technical difficulty.this paper proposes a method of indirect compensation according to the error of machining workpiece,we adjust the parameters of the hobbing processing according to the measurement result of the pitch error of the gear,and control the meshing relationship between the hob and the workpiece.This method has the advantages of simple operation,low cost,and high compensation efficiency.The specific research contents are as follows.First of all,based on the source of machining error of CNC gear hobbing machine,this paper establishes the mathematical model of the pitch error of hobbing processing;According to the principle of gear meshing,the various errors in the processing of the hob are converted into the gearing line error.Then,by using the relationship between the gearing line error and the cumulative deviation of the pitch,a mathematical equation for the relationship between various machining errors and the pitch error is obtained.Finally,the equations of the mathematical models of various errors are superimposed,and the mathematical model of the pitch error in the hobbing of CNC hobbing machine is obtained.Secondly,according to the mathematical model of the pitch error in the above-mentioned CNC hobbing,the mathematical model of the pitch deviation compensation is established.The method of on-machine compensation and the solution of error compensation amount based on harmonic decomposition are described.The CNC program for hobbing error compensation is programmed based on the error compensation amount and the NC program is inserted into the system of CNC.By controlling the meshing relationship between the hob and the workpiece,the compensation of the gear hobbing error is realized.Finally,the models of CNC gear hobbing machine tool and the hob tool are built by Pro/E and SoildWorks,and the models are imported into VERICUT software to complete the simulation experiment of gear hobbing compensation.The virtual gear measurement center(VGMC)is used to measure the pitch deviation and the cumulative deviation of the pitch of the simulated gear to obtain the simulation results.The simulation results of machining compensation show that,by the method proposed in this paper.for the large gears with diameters more than 500 mm,the compensation efficiency(equal to the difference between the error value before compensation and the error value after compensation divided by the error value before compensation)is between 37% and 47%,which can improve the accuracy level by one.for small gears with a diameter less than 500 mm,The compensation efficiency is between 48% and 60%,and the stability is improved by 2 levels,The compensation effect is very obvious.Therefore,the correctness of the machine compensation method for the gear tooth hobbing of the large gear hobbing is verified.