1. Fine design of processing adjustment parameters
The existing tooth surface processing design and modification methods are: Based on the local conjugate principle, the small wheel processing parameters are calculated from the large wheel processing parameters, and the small wheel pre-control parameters are adjusted or the processing parameters are recalculated by adopting the proportional correction technology after TCA analysis. The effect of this method can only be obtained through TCA analysis, and the process is cumbersome. At present, Gleason and klinberg have developed a new tooth surface correction technology: tooth surface topology correction technology based on ease off. This modification method is integrated into Gleason’s cage software and klinberg’s kimos software. Scholars in domestic universities have also developed similar design software. Compared with the traditional modification method, the modification method of the software is not only intuitive, but also avoids the complex calculation of curvature and torsion. It can be used not only for the involute spiral bevel gear processed by end face milling method, but also for the equal height bevel gear processed by end face hobbing method.
Ease off is a graphical expression of the relative geometric topological shape of two tooth surfaces. It can show various mismatch relationships between small wheel and large tooth surfaces in a pair of gear pairs and be applied to the correction of machining parameters. When the pinion and the gear tooth surface are completely conjugate, ease off shows that the two tooth surfaces coincide. When modifying the tooth surface, it is not to modify the traditional adjustment items, but directly modify the tooth surface topology. The tooth surface shape is controlled by changing five parameters: helix angle error, pressure angle error, tooth length drum shape, tooth profile drum shape and tooth surface torsion. The change of each parameter will cause the change of tooth surface topology, and the matching effect of conjugate tooth surface can be observed intuitively.
2. Networked closed-loop manufacturing technology
Compared with ordinary gears, the tooth surface geometry of curved bevel gear of automobile drive axle is particularly complex. It is more difficult to express the tooth surface equation, adjust the cutting process and correct the tooth surface deviation, which determines that its processing and manufacturing needs networked closed-loop manufacturing technology. Through the construction of network integration environment and platform, the design and calculation technology, NC machining technology, tooth surface digital detection and correction technology, vibration and noise detection technology and management control technology of curved bevel gear are organically combined, and through the information integration and feedback control of each link, as well as the overall management of manufacturing link and information, Realizing the informatization and integration of curved bevel gear machining process can effectively improve the tooth surface manufacturing accuracy, meshing quality and production efficiency of curved bevel gear.
In the networked closed-loop manufacturing system, firstly, parametric drawing, tooth surface contact analysis and motion error analysis are carried out. Through the correction of tooth surface contact area and transmission error, the tooth cutting adjustment card containing the optimal machine tool adjustment parameters and tool parameter values is finally obtained. The NC gear milling machine tool can perform rough and fine cutting of large and small wheels, or full process machining. Then, the tooth surface error of large and small wheels after trial cutting can be measured and corrected respectively on the gear measuring center, and finally the actual optimal machining parameters meeting the accuracy requirements can be calculated, which can be returned to the NC gear milling machine tool through the network to re trial cut and correct the machining parameters, It changes the traditional manufacturing mode, that is, the correction method of transmitting the machining parameters of the tooth surface through manual correction of the small wheel and paper. In the process of reverse adjustment and correction, due to the digital reverse adjustment and correction technology based on tooth surface detection, only one or two trial cuts can meet the design requirements, which not only improves the machining efficiency, but also ensures the tooth surface accuracy. At the same time, it can give full play to the high-efficiency machining potential of NC gear milling machine. After the tooth surface detection and correction, the gear pair can be tested for its transmission accuracy and vibration and noise on the roll inspection machine. After the test results are analyzed and processed, the meshing performance of the gear pair can be evaluated as a whole, so as to form a networked closed-loop manufacturing system based on design, machining, tooth surface measurement and meshing performance detection.
3. Precision forging near net shape technology
At present, the traditional milling technology is still used in the manufacturing of curved bevel gear of automobile drive axle in China, which has the advantages of low material utilization, high energy consumption and low production efficiency. As an advanced manufacturing technology, precision forming technology is gradually developed on the basis of traditional die forging technology. This process overcomes the defects such as low utilization rate of cutting materials, low production efficiency and reduction of bending strength caused by cutting off the metal fiber streamline. It is in line with the development trend of advanced manufacturing technology in the 21st century, which is efficient, precise, green and clean. It is one of the main ways for the machining reform of curved bevel gear of automobile drive axle in the future. In recent years, the precision forging technology of spur bevel gears has developed rapidly. From the initial hot forging to cold precision forging, the quality of forged gears has been greatly improved. Relevant technologies have been industrialized and mass production in many domestic enterprises. The precision forging of the driven wheel (crown wheel) of the curved bevel gear of the automobile drive axle has achieved gratifying results in recent two years. The bench test shows that the service life is increased by 70%. Through the in-depth research on the precision forging near net shape technology and post forging processing technology of curved bevel gears, China has solved the key problems affecting the mass production of automotive drive axle driven gears in the precision forging process, and the forged driven gears (crown teeth) can be used only by precision machining. The use of precision forging near net shape to replace all gear cutting processes before hot finishing not only saves materials, but also improves machining efficiency and reduces the manufacturing cost of gears.