Study On Electrochemical Finishing Process For Spiral Bevel Gear

Having favorable working performances, spiral bevel gear (SBG) has been more and more used, and also becomes one of the key parts in automobile manufacturing. Meanwhile, it is increasingly shown that the influence of the machining quality of the gear on its working performances. Lots of studies and practices have demonstrated that part's working performances could be enhanced greatly by improving its quality of the surface, which is obtained by the finishing method. Therefore, if the surface of SBG is finished, its service performances will be enhanced undoubtedly.As an unconventional and noncontact finishing method, the electrochemical finishing (ECF) method has been developed rapidly as a result of its advantages such as regardless of material hardness, high material removal rate and smooth micro-profile of the obtained surface, and thus the method has been used in finishing some key parts to achieve better surface quality. The finishing practice has indicated that ECF not only can improve the surface quality largely, but also can reach good dimensional accuracy. Hence, it is of great significance to apply ECF to finish the teeth surface of SBG for improving its machining quality.Aimed at the domestic machining condition of SBG, which is used in automobile's driving axle in our country, and for the requirements of Changchun FAW (First Automobile Works), this paper has analyzed the finishing methods of SBG both in home and abroad, combined the condition in application and research of ECF both in home and abroad, especially in the achievement of DLUT in ECF, and then put ECF forward as finishing method for better machining quality of SBG.Because of the factors such as SBG's geometry structure, the machining quality of SBG and the finishing mechanism of ECF, there are many difficult problems on utilizing ECF to advance the machining quality of SBG. These difficult problems not only relate to the mechanism of ECF and a good selection of the ECF methods, but also relate to the application of the selected ECF process.Considering the difficult problems in the finishing surface of SBG with ECF, the research, focusing on the finishing mechanism of ECF, has been carried out, and the mathematic model, explaining the electrochemical dissolution (ECD) of anodic surface micro-profile in the condition of small gap, has been brought forward according to Faraday's law. Based on the analysis of theory and experiment, it has been discussed that the influence of the change in anodic micro-profile on finishing effect during the process of ECF from the view of the micro-geometry. The research results show as follows: the ECF is just the ECD in the condition of the small gap, and its characteristic is that the rate of ECD is uneven distribution along with the anodic mico-profile; the finishing process of ECF is the process of blunting the anodic surface micro-profile, which does not only influence the improvement of finishing effect, but also leads to the memory effect of the anodic micro-profile; it can improve the smooth effect of ECF that decreasing the distance between electrodes and making anodic surface micro-profile sharp.Based on this, taking optional methods of ECF for SBG into account, this paper has analyzed the related key processing problems such as the cathodic surface quality, the effect of pulse electricity, the function of mechanical role and the anodic original surface quality.The research result indicates that after the smooth process of ECF, the achieved anodic surface micro-profile is related to the anodic surface micro-profile, the cathodic surface micro-profile, and the uneven distribution of anodic materials as well. The existence of relative movement between the electrodes and its combination with the pulse current are helpful for applying the cathodic high-point-scanning to improve the surface quality and better accuracy of anode also. The mechanical role, which exists in the electrochemical mechanical finishing (ECMF), can not only contribute to the function of scratching, but also sharpen the anodic surface micro-profile. According to the anodic original surface quality, it can improve the smooth effect obviously that enhancing the action of the mechanical role of ECMF properly.Combing the characters of SBG's geometry structure, through comparing the different advantages of pulse electrochemical finishing (PECF) with moving cathode and ECMF, the former one has been chosen to finish the surface of SBG. At the same time, through the analysis of SBG structure, it has been discussed that the application model of cathode with moving in the finishing process of SBG, and then the flow-field between the electrodes has been also designed.According to above-mentioned analysis, the chosen method has been carried out by using the mechanical machining tool of SBG. The experimental result reveals that the SBG with the surface roughness Ra0.1μm and machining accuracy DIN7, which was machined with forming shape method, can be achieved by using the PECF with moving cathode.The experiment result shows that the topic of the dissertation is an advanced, and the ECF process can improve the machining quality of SBG effectively.