A Study On Milling Kinematics And Machining Accuracy Of Large Diameter Internal Thread

The traditional machining methods,such as turning and tapping,have some restrictions on the machining of large diameter internal threads.Therefore,this paper chooses milling as the processing method of large diameter internal threads.In the process of milling large diameter internal threads,the choice of different cutting parameters would lead to different degrees of changes in surface quality and machining accuracy.Therefore,the main research content of this paper is milling large diameter internal thread,including the following aspects:At first,base on that principle of internal thread milling motion,the mathematical model of any point on the cutting edge of internal thread milling is established.The single-factor experiment method is used to simulate any point locus on the cutting edge under different cutting parameters,tool diameter and number of cutter teeth by MATLAB simulation software.The conclusion is drawn that with the increase of cutting speed,tool diameter and number of cutter teeth and the decrease of feed rate,the theoretical roughness will be reduced,and the theoretical roughness will be close to the ideal smooth surface.Then the mathematical model based on the theoretical roughness are established and the factors influencing the theoretical roughness are supplemented and analyzed.Secondly,on the basis of theoretical analysis,the machining accuracy of internal thread milling is tested by orthogonal experiment under the conditions of different cutting speed,feed per tooth and overhang of milling cutter.The corresponding experimental data were obtained by using the screw thread synthesizer.After recording and calculating and analyzing,it was concluded that with the increase of cutting speed,the feed per tooth and the overhang of the milling cutter decreased,and the dimensional accuracy error of the internal screw thread decreased.The cutting speed has the highest significant error to the dimensional accuracy,followed by the cutter overhang and the feed per tooth.Finally,the three-dimensional model of thread milling cutter and workpiece is established based on UG three-dimensional modeling software,and the residual stress of milling internal thread surface is simulated by single factor experiment method based on DEFORM-3D finite element simulation software.The conclusion is that the residual stress of workpiece increases with the increase of cutting speed and feed per tooth,and the influence of cutting depth on the residual stress is small.Based on the analysis of the roughness forming principle of the internal thread milling theory,the factors influencing the machining accuracy error and the residual stress forming mechanism,the change trend of theoretical roughness,machining accuracy and residual stress of internal thread milling with cutting speed and feed rate per tooth is obtained,which provides valuable reference for improving machining process and surface quality and machining accuracy of machined materials and has certain guiding significance.