Research On NC Machining Methods Of Line-Contact Spiral Bevel Gears

In order to solve the deficiency of the tooth surface design theory and correction method of the spiral bevel gear based on the local conjugate principle under the condition of digital advanced manufacturing technology,this thesis carried out the NC machining methods of line-contact spiral bevel gears.Firstly,the mathematical model of the tooth surface of line-contact spiral bevel gear was established.Then the NC machining technology advantage was used in subjoining additional cutting movement,based on traditional cutting process.By establishing the geometric topological deviation model of the pinion machining tooth surface in comparison with the pinion theoretical tooth surface and the correction mathematical model of machine tool adjustment parameters,the pinion tooth surface processing compensation parameters were determined.Finally,the research results were confirmed through finite element contact analysis and NC cutting simulation,and the theory and technology for NC machining of line-contact spiral bevel gears were determined.The main research contents of the thesis are as follows:(1)The mathematical model of the tooth surface of line-contact spiral bevel gear was established,and the mathematical models of conjugate tooth surface meshing equation,tooth surface equation and two kinds of boundary lines characterizing the geometric characteristics of tooth surface engagement were obtained.Setting the gear tooth surface as priority processing,the gear machining tooth surface equation was obtained by using generating method.Thus the pinion tooth surface equation in line-contact conjugate meshing with the gear tooth surface was obtained.(2)Based on the machining principle and calculation method of machine tool adjusting parameters of the tilting method,the machining roll ratio of pinion tool tilting method was modified with the advantage of NC machining technology.And the pinion machining tooth surface equation was obtained by establishing the cutting motion model of the pinion in traditional cradle milling machine.By comparing the pinion machining tooth surface with the pinion theoretical tooth surface,the geometric topological deviation model of the pinion machining tooth surface in comparison with the pinion theoretical tooth surface and the correction mathematical model of machine tool adjustment parameters were established.Then the pinion tooth surface processing compensation parameters were determined and the tool movement path planning was realized by using the modified calculation method of tooth surface correction.(3)The 3D models of pinion and gear were established.After that,finite element contact simulation analysis was carried out on the assembled gear pair model.The results showed that the gear pair in the process of transmission meshing was line-contact in all instantaneous states with several teeth were engaged in meshing at the same time,which verified the validity of the tooth cutting method and tooth surface correction calculation.(4)The NC machining method of line-contact spiral bevel gear was studied.Based on the five-axis machining center with double rotary tables,the cutting motion model of pinion was established.According to the same condition of the relative position of the cutter plate coordinate system and the tooth blank coordinate system in traditional cradle milling machine and NC machine tool,the motion parameters equations of each axis in the five-axis machining center were solved.And the cutting motion model of pinion was transformed from traditional cradle milling machine to NC machine tool of five-axis machining center.Through NC machining simulation,the tooth cutting model,motion transformation and NC machining programs were verified.