| Spur gears, whose precision forging process is an advanced gear forming technology, are typical drive parts applied widely in mechanical industry. There are lots of merits by using the process, such as great gear mechanical property, high production efficiency, saving materials, great precision and surface quality, it can adapt to the trend of the advanced manufacture technique with the advantages of high efficiency, precision and energy-saving, and in the future the precision forging technology will be the most important method for gear manufactory.Based on the fundamental principles of positive friction and restrained distributaries, taken a small gear with hole that number of teeth is 18 and the modulus is 2.5 as the research object, the precision forging processes of spur gears with solid billet and hollow blank were studied by the method of physical experiment and numerical simulation which aim at the questions on difficult cavity filling and high forming force in the precision forging of spur gear.The physical experiment results show that positive friction is not only to lower the forming force of gear precision forging with solid billet, but also can be obtained good filling effect; in contrast, regardless of with or without positive friction, the filling effects of spur gear with hollow billet were good, the influence of forming force was also lesser. At the same time, through the contrast analysis of gear forming effect and the final load size, the optimum schemes were proposed: if the solid billets were used, the forming of the gear was better when web was in mid-upper position, it is the best web position; if the hollow blanks were used, small mandrel distributaries in the form of movable container, the size of blank isΦ38 mm×Φ16 mm×27.3 mm, and lugs distributaries in the form of fixed container, the size of blank isΦ38 mm×Φ18 mm×25.7 mm, these are two kinds of the best schemes for the best filling effect and the least forming force in the hollow blank gear forming process.On the basis of the commercial FEM software DEFORM-3D, the finite element model of spur gears precision forging process which is accord with the experimental conditions of process and parameters settings on various programs were established for the numerical calculation. Compared with the experimental results, no matter gears forming effect and load-stroke curves, it shows better fitness and effectiveness of the analysis model which can investigate the influence of the metal flowing law and process parameters on the forming force during the precision forging process of spur gear. The analysis demonstrated that stress, strain, temperature and forming force are high in the area of difficult filling (usually occurred at the transitional section of gear involutes and dedendum circle, top and bottom horn gap of addendum); The process parameters of fillet radius, extrusion speed and friction condition are the main factor to effect the final forming force, they should be chose carefully in the actual production.Finally, according to the proposed optimization scheme and the process parameters, the gear extrusion forming process of steel blank is simulated. Simulation results show that the gears forming effect of the solid billet and the hollow blank are good and the variation trend of load-stroke curves agree with lead blank, the referential gist was provided for practical production.
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