| Gear is the key parts in the transmission machinery such as auto transmission,robot joint reducer and electric vehicle reducer.The machining accuracy and efficiency of its tooth surface have great influence on the development of transmission machinery.Power skiving is a gear machining method based on the meshing theory of two degrees of freedom of line and surface.It can realize the high efficiency and high precision machining of gear,especially in the machining of internal gear.The process parameters of power skiving have obvious influence on tool wear.If the process parameters are not reasonable,the tool wear will be too fast and the quality of gear machining will be affected.In addition,the vibration in the cutting process will form inconsistent vibration lines on the tooth surface,which makes the workpiece tooth surface precision deteriorate.Therefore,in order to improve the service life of the tool,improve the machining accuracy and surface quality of the workpiece,this paper carried out an in-depth study on the tool wear mechanism and the formation mechanism of the tooth surface vibration during the power skiving process,in order to achieve the optimization guidance of the power skiving process.The main research contents of this paper are as follows:(1)Research on motion and force analysis and simulation of power skiving process.Based on the 3D cutting model of gear and process principle,the motion of gear and the force of tool shaft were analyzed,the theoretical model of gear force calculation was established,and the force variation law of gear tool shaft was obtained.SPH meshless method was used to simulate the cutting process of gear teeth,which solved the problem of mesh distortion disappearance when the cutting layer thickness was thin based on mesh method,realized the formation process of complete chip cutting,and provided guidance for the research of complex chip formation mechanism.The changing law of cutting force of gear teeth was analyzed,and the stress and temperature changes in each area of cutting edge were analyzed,and the most prone to wear deformation area of the three cutting edges of the tool was obtained.(2)Modal analysis and response Research of power skiving tool system.The frequency response function of tool system was obtained by modal test.The frequency response function of simulation and experiment was identified by rational fraction polynomial method,and the modal parameters of tool shaft were obtained.Based on the finite element method,the mode shapes of the ten-order system near the first order natural frequency of the tool shaft are studied,and the regions which are more prone to vibration in the tool system structure are obtained.The response analysis of the tool spindle under transmission error excitation shows that the vibration sensitive direction of the tool spindle is X direction.With the aim of maximizing the stiffness,a new tool holder was designed and the response of the tool holder with two different structures was analyzed under the drive error excitation.Based on the Newmark method,the displacement response of tool system under the gear force excitation corresponding to different speed was analyzed,and the influence law of different speed on the workpiece surface vibration was analyzed.(3)Stability analysis of power skiving machine.Based on cutting force analysis and modal analysis of power skiving process,the dynamic equation of power skiving tool system was established,the dynamic equation was solved based on semi-discrete method,and the eigenvalue of state equation was determined based on Floquet stability criterion,so as to obtain the blade diagram of power skiving process stability,so as to predict the chatter in machining process and guide the optimization of process parameters.The influence law of different modal parameters on the blade diagram is analyzed to provide theoretical basis for the structure design of power skiving machine. |
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