Research On The Key Technology Of Face Milling Cycloidal Gear On Five-axis Machine Tool

The quality defects of domestic cycloid reducer mainly include the poor transmission accuracy, unstable movement, low bearing capacity, and short life. The root cause of these problems is the finishing technology of machining the gear tooth profile. At present, the grinding machine is widely used to finish the tooth surface of the cycloidal gear. Due to the tool structure, the tooth profile accuracy and the surface quality of the cycloidal gear are poor. So the transmission precision, the transmission stability and the service life of the reducer are greatly reduced. This problem is particularly prominent in the manufacture of small speed reducer. The key to solve the problem involved in the production of high-grade cycloid reducer is to guarantee the precision machining quality with efficiency.The research on high speed face milling cycloidal gear on five-axis machine tool will focus on such aspects as the tool path planning methodin precision milling, the model construction of milling force and coupling milling deformation of cycloidal gear, analysis of chatter stability and optimization of milling parameters for the cycloidal gear, high speedmilling test and precision analysis for the cycloidal gear. The main researches are as follows.(1) A method of non interference tool path generation for face milling cycloidal gear on five-axis NC machine tool is proposed.Based on the tool rake angle and side inclination angle, the effective cutting ellipse mathematical model of face mill is established, and the approximate calculation formula of cutting width of face mill is derived. A method is proposed to solve the problems of local interference and the collision interference of face millby using the tool rake angle and side inclination angle respectively. The calculation formula of the tool rake angle for machining cycloidal gear without interference is obtained; the expression of row spacing to machine the outer convex and concave tooth profile of the cycloidal gear is derived. The geometric model and numerical control simulation model of face milling cycloidal gear are established, and the tool path is obtained. The results of numerical simulation show that the setting of parameters is reasonable, the tool pathsare smooth, and there is no machining interference.(2) The models of dynamic milling force and the coupling milling deformation for face milling cycloidal gear are established.The dynamic milling force model is established based on instantaneous rigid milling force formula, and the milling force simulation of face mill is carried out on the basis of the model. The model of coupling bending, distorting, and shearing deformation is established based on the theory of elastic mechanics. The finite element analysis of the milling deformation of the cycloidal gear is carried out by using the software ANSYS. The milling deformation of the cycloidal gear in circumferential direction is obtained. The effects of different milling parameters on the stress and strain of the cycloidal gear are analyzed.(3) The dynamic mathematical model of tool-workpiece is established, and the calculation method for predicting milling stability limit is put forward. The whole machining system is divided into two subsystems: "tool-spindle" and "workpiece-clamp". The experimental modal analysis is carried out, followed by deriving the corresponding frequency response function with modal parameters under different conditions. The chatter stability field lobes related to the spindle speed and the axial cutting depth are obtained. Finally, the accuracy of the analytical method of the chatter stability domain is verified by the experiment of the face milling of the cycloidal gear.(4) The precision machining technology of the cycloidal gear is used as the research object. A multi-objective optimization scheme of milling parameters based on the dynamic characteristics of machining system is presented. A multi-objective optimization model of milling parameters is constructed with the spindle speed, feed per tooth, axial depth and radial cutting depth as the design variables with the maximum productivity and the minimum cost as the objective function, the performance of machine tool, cutting tool performance and machining quality constraints as constraint conditions. The stability of the machining system is used as the key constraint to optimize the milling parameters. The results of simulation and experiment showthat the surface quality might be improved and that the deformation of cutting tool and the machining cost mightbe reduced, to a certain extent, by using the optimized milling parameters.(5) The NC machining process of the cycloidal gear is designed. The high speed face milling process of the cycloidal gear is realized by using five axis linkage vertical machining center, and the cycloid gear prototype after finishing is obtained. The three coordinate measurement and error evaluation method of the tooth profile for the cycloidal gear are proposed. The roughness of the tooth profile of the cycloidal gear is measured with the contact contour instrument. The method can realize the goal of "by milling instead of grinding" in machining cycloidal gear, and improve the processing efficiency.