Process For The Cold Precision Forging Of Spur Gears And The Modification Of Tooth Profile

Spur gears are mainly manufactured by metal cutting or by a combination of conventional hot forging with machining, which results in high production cost and much manufacturing time. Precision forging of gears has a lot of advantages compared to conventional gear shaping, because it allows the manufacture of gear parts without flash and consequently without the need for subsequent machining operations. Therefore, the implementation of such a technology is capable of providing important economic benefits in terms of raw material and energy savings, and also achieve considerable cost saving due to higher productivity. In recent years, the development of precision gear forging process has been an area of increasing activity. As one of the 863 Programs, this thesis aims at a detailed investigation of cold precision forging of spur gearsThe study in this thesis were performed by the combination with numerical simulations and experiments. Firstly, the CAGB of spur gears using VBA was realized, which solved the problem of tooth profile drawing in AutoCAD2000. Then, the rigid-plastic FEM was introduced and several important problems in simulation such as convergency and remeshing were discussed. And plenty of simulations and experiments have been carried out to analyze thevarious processes of gear forging, and several factors such as the friction factor, which had great influence on the radial flow of the material, have also been investigated. As a result, the equilibrium filling concept has been put forward.To make up for the deficiency of the graphical display in post-process of DEFORM, a new method that can automatically obtain the profile of the object has been achieved, which made it possible to catch the slightly deformation of the die. Additionally, lots of simulations and experiments were done to analyze the different factors influencing the gear tooth accuracy, such as the elastic expansion of die and the spring-back of the forged gears. Consequently the deformation mechanism of the closed die has been obtained and a new method of tooth profile modification was put forward. At last, with the improved forming process and accuracy control operation in this thesis, series of experiments of precision gear forging have been implemented.The result of the measure about the forged gear is satisfied.The accuracy has reached class 8^th according to GB10095, and the effort in this thesis has provided a basis for the accomplishment of the 863 Program.