Numerical Simulation On Precision Forging Technology Of Spiral Bevel Gear

At present, the traditional manufacturing technique of spiral bevel gears as the metal cutting method, has many disadvantages, such as inefficient use of material, low productivity, high production cost. The traditional manufacturing technique will not meet the demands of companies. Using precision forging process to produce spiral bevel gears, the material and power are saved, the cost is reduced and the efficiency is enhanced. A t the same time, mechanical properties and the service life of the precision forging spiral bevel gear are improved The forming laws of gears precision forging, especially spiral bevel gears, have not been investigated completely because of the complicated geometry of gear, many influencing factors and plastic deformation with difficulty. It is very important to research the precision forging process of spiral bevel gears considering the conditions of our gear industry improvement.On the basis of investigating lots of techniques of gear forming process, the modified process with central relief based on the divided flow method is introduced in this paper. In this process, the central relief concave is forming by the upper and lower convex punches in the performing; the gear die cavity is being filled when the material is filling the central relief concave in the final forging. The central relief concave will not be filled completely when the gear die cavity is filled completely. There is still unfilled concave space, so the material can flow freely. Therefore this process can improve the filling property of material and reduce the forming load. The geometry of central relief concave is very important. Three kinds of convex punches such as sphere, cylinder and cone, are selected in order to analyze the influence of central relief concave on forming process. The effective stress distributions and the load-stroke curves are obtained by numerical simulation. The simulation results show the cone is the optimum geometry of the punch. The 3D model of spiral bevel gear is established using PRO/E, 3D finite element simulation software DEFORM-3D is used to simulate the forging process of the central relief based on the divided flow method and the conventional closed die forging with solid bill. Some parameters, such as stress, strain, temperature, velocity and load of forging, are compared for the two forging technologies. Results indicate that the forging technology of the central relief based on the divided flow method has many advantages, such as small load, small stress and well-proportioned temperature, compared with the conventional closed die forging.3D rigid-plastic FEM is employed to research the enclosed die forging process of spiral bevel gear. The influences of parameters, such as technological parameters (the billet temperature, the deformation rate and friction coefficient) and structure parameters of spiral bevel gears (modulus, tooth number, helix angle and pressure angle) on precision forging are simulated frequently. the influence of these parameters on forging process is analyzed according to the simulation results, the influence law of these parameters at the closed die forging process of spiral bevel gear is obtained. The simulation results indicate that the forging load decreases with the increase of the deformation temperature, the deformation rate and the decrease of the friction coefficient. The forging load and equivalent stress of dedendum increase with increase of the modulus and tooth number, while the helix angle and pressure angle have little effect on the forging load and equivalent stress of dedendum as other parameters keep invariable. All the studies may provide the reference for the die design and technology layout of precision forging of spiral bevel gear.