Research of Key Technologies for High Efficiency and Low Cost Rough Machining of Curved Tooth Bevel Gears
Supervisor:deng xiao zhong
Nowadays,curved tooth bevel gears(this paper refers to spiral bevel gears,cycloid bevel gears and curved tooth inner bevel gears)are widely used in automobile,engineering machinery,helicopter,ship,port machinery and so on.The demand for high quality curved tooth bevel gears in domestic market is great,five-cut method will be phased out as its low process efficiency and low accuracy.In recent ten years,two-cut method was introduced into China from developed countries.However,tool consumption is serious due to the lack of mature technology in the control of homogeneity of wheel blank material and isothermal normalizing.Besides,the expensive imported CNC equipments further increase the cost of gear processing.Therefore,it is difficult to satisfy for the requirement of large quantity and low cost of the curved tooth bevel gears used in automobile and engineering machinery.By contrast,the four-cut method,which is divided into rough processing and finish processing,is more suitable for our national conditions.Rough machining is finished on domestic milling machine using traditional cutting tools,and less margin is left for finish cutting,which relieve the cutting tool consumption and reduce the cost of gear effectively.In this paper,the key technologies such as the optimization of feed speed,the match of rough and finish machined tooth surfaces,optimization of machining parameters in rough processing and high efficiency machining of curved tooth inner bevel gears are studied,exploring the high efficiency and low consumption rough cutting machining method of curved tooth bevel gears suitable for our country.The followings are the key results and innovations of this paper.(1)Research of forming rough cutting force and processing efficiency are carried out,and calculation method for determining the depth and thickness of instantaneous cutting area is proposed,the number and type of real-time working cutting blades are judged.By the oblique cutting theory,multi-blade cutting force is completed,and the calculation theory of equal cutting force is constructed.Then,the experiment of forming cutting force collection is completed on the basis of finite element analysis technique,the high efficiency rough machining is realized,and the precondition is established for the implementation of the four-cut method.(2)Research of generating rough cutting force is conducted by referring to forming cutting force model.According to the positional relationship of the instantaneous cutting area and tooth surface,the instantaneous cutting depth and thickness in five stages are determined,and the calculation theory of tangential cutting force which coincides with the actual working condition is built,the calculation of cutting area and cutting force in different areas is completed.Then,the experiment of cutting force collection is carried out,the control of equal cutting force feed is realized,and the cutting efficiency is improved effectively.(3)On the basis of studying the characteristics of spiral bevel gears and cycloid bevel gears,general mathematical models are established for forming and generating methods,and the numerical control equivalent conversion of the generating method is accomplished,and the motion polynomial of the working axis is carried out.The initial rough machining parameters and initial tooth surface error are calculated,which lays a theoretical foundation for the low consumption rough machining of cycloid bevel gears..(4)The approach for rough machining cycloid bevel gears with spiral bevel gear cutter is studied.According to the general mathematical models and the initial machining parameter calculation theory,aiming to optimize the forming parameters and the coefficients of the motion polynomials by generating method,the parameter optimization program is written.Finally,on the basis of virtual machining simulation analysis,the experiments of the cutting area comparison and the matching of finishing and roughing tooth surfaces are carried out,and the low consumption of cycloid bevel gear is realized,which provides a new idea for the cost control of enterprises.(5)The machining method by using disc milling cutter to process the curved tooth inner bevel gears is proposed.The unique vertical tilt angle is calculated,and the cutter position and the sliding base are compensated.The pressure angle and the spiral angle of the internal bevel gear reference point are obtained,and the correction of the tooth surface pressure angle is realized by adjusting the machining parameters.Subsequently,the experiment for high efficiency gear processing is carried out by equal cutting force feeding,which provides a new method for the efficient manufacturing of curved tooth inner bevel gears and precision forging die of curved tooth bevel gears.