Precision forging die processing of spiral bevel gear is the main means of rapid product development in industry for a long time. Die processing is an effective way to reduce production cost. In the past, the dies of spiral bevel gears were mostly machined by EDM. With the development and progress of NC technology, NC machining has become a more advanced way of die machining; EDM die processing is applied in mechanical processing and other fields. Machining spiral bevel gears by die method has the advantages of low cost, high efficiency and high consistency of finished products. Therefore, the way of forging spiral bevel gears is more and more widely used, and the advantage is more obvious for mass production, from injection molding Forging forming and powder metallurgy forming technology can be reflected.
The principle of electrical discharge machining (EDM) is to use pulse power supply for discharge. One end of the power supply is connected to the workpiece electrode and the other end is connected to the tool electrode. A very small discharge gap is reserved between the two. When there is pulse voltage between the two poles, the workpiece and the tool generate instantaneous high temperature in the discharge area through instantaneous high-energy discharge, and the material of the workpiece is melted and evaporated, If a gap is formed and the cyclic pulse voltage is used for continuous discharge, the tool electrode shape will be copied to the workpiece to complete the machining. The EDM technology is now relatively mature. Because there is no machining taper, it is widely used in the field of mold machining. The EDM of spiral bevel gear mold belongs to the generation method. The tool electrode is used to simulate the meshing with the gear, and the tooth shape can be copied to the mold. This method can mainly process the molds such as spur cylindrical gear or spur bevel gear. Due to the high die stress during forging and obvious elastic deformation during bearing, the die must be able to distribute and bear this deformation and stress, and the spiral bevel gear die is required to have high precision and high strength. The method of EDM machining spiral bevel gear mold has been favored by enterprises for a long time because EDM has the advantages of removing materials, no mechanical force, unlimited workpiece hardness and internal structure, no machining taper, and homogenizing the machining error of each tooth.
Although the method of EDM machining spiral bevel gear die is widely used, its disadvantages still exist and restrict the further development of die machining. In the process of EDM die, there are certain manufacturing errors, including electrode tooth surface machining errors, general forming machining errors, as well as machining errors caused by electrode wear, secondary clamping errors and EDM parameters. In addition, in the EDM of spiral bevel gear die, the poor machining environment and difficult slag removal will affect the accuracy of die machining, reduce the accuracy of the final die, and violate the high-precision attribute of the die.
For the EDM of spiral bevel gear die, especially for small module spiral bevel gear, the error of electrode machining tooth surface is large, which makes the accuracy of die very low. Generally, the meshing performance and tooth surface accuracy of forged spiral bevel gear forgings are difficult to achieve high goals, and good contact area cannot be obtained, which has a great impact on the transmission performance of spiral bevel gear, It limits its application in spiral bevel gears. Therefore, the NC machining method can be used to make up for the lack of accuracy in EDM. If the pitch cone angle of spiral bevel gear pair is large enough and it is easy to get out of the mold, the NC machining method can be used to make the mold.
When the spiral bevel gear is processed by the die method, the accuracy and performance of the die directly determine the final result of the die method. In this paper, the mold model is accurately established by UG, and the tool path and machining program are generated under its machining module. The machining code is converted according to the corresponding NC machine tool, and then the mold is processed in the precision machining center; This method can improve manufacturing accuracy, reduce machining links, simplify die repair process, and overcome the shortcomings of EDM.