The Study On Some Key Technologies Of Rotary Forging Process For Spiral Bevel Gear

Spiral bevel gear is the core of differential mechanism, for their features of high carrying capacity, high stability, space-saving and so on. However, the manufacturing process of spiral bevel gears mainly depend on the special Gleason machine tool, since the tooth surface geometry of such gears is quite complex . Plastic forming has some advantages, including the reduction of waste material, the improvement of the production coefficient, gear strength and life, and overcome the shortcomings, not easy machining by cutting. Rotary forging is a partly presswork succession plasticity forming and decreases the load of die forging spiral bevel gear, so it is a new technology of plastic forming of spiral bevel gear.As a new technology, it lacks of experiments and date to make technological plan. In addition, because the tooth curve of spiral bevel gear is long and curving, metal flows complexly and die often fails from fracture, which is the bottleneck for the implement of rotary forging spiral bevel gear. Metal flow, die stress, load change trend being analyzed deep will accelerate this process develop and implement.In this paper, the rotary forging process of spiral bevel gear was studied based on finite element method. The main results are as follows:(1) Based on UG software, through programming spiral bevel gear tooth curves were generated and 3D models of spiral bevel gear and die were established.(2) Based on DEFORM software, the rotary forging process of spiral bevel gear was simulated. Through the study on the rotary forging process of spiral bevel gear, the deformation and load at every stage are obtained and the tooth filling character as well as; analyzing the formation of the inside, outside mid-point at the addendum, dedendum of the convex and concave surface spiral bevel gear, the reason that the outside is difficult to fill was explained. Via the lead specimen test, the validity of the rotary forging process of spiral bevel gear from simulation was verified .(3) For the large flash and the excessive load, the improvement of the punch profile was proposed. It led to the reduction of flash area and the decrease of forming load by 1/3 from simulation, and through theoretical calculation, the validity of the improvement of punch was verified.(4) Some points at the addendum on its convex surface and concave surface of the die are selected to study circumferential and radial Stresses. And stresses and unbalanced stresses at the addendum are analyzed. The main reasons why the die always fractures are obtained that the stresses on convex surface of the outside section and unbalanced stresses at the outside section are too large .Improving the strength at the outside section and at the middle section can improve die life in rotary forging process of spiral bevel gear.