The processing methods of the tooth mold electrode mainly include: gear machining, milling machine machining and machining center CNC machining. Among these three processing methods, the gear cutting machine has the lowest machining precision, and the electrodes processed by the new factory can reach ISO7-8, the milling machine has better machining precision, and the processed electrode can reach ISO 6-7. The highest precision is the electrode machined by the machining center. The precision machining center can process the electrode to ISO 4~6. At present, all major gear precision forging manufacturers and some universities in China are developing machining center processing technologies for planetary gears and semi-axle gear electrodes. For example, Jiangsu Pacific Precision Forging Co., Ltd. and Qingdao Samsung Precision Forging Gear Co., Ltd. have made breakthroughs. FAW Technology As early as 2002, the pressure chamber of the central technology department developed the machining technology of the planetary gear and the half shaft gear tooth mold electrode (see Figure 1, Figure 2) and the machining center of the standard gear, and controlled the precision of the electrode and the standard gear. In ISO 4 to 5 levels. In recent years, breakthroughs have been made in the control of tooth engagement and contact zone, so that the deformation of the tooth profile during the forming process and after forging, and the subsequent heat treatment can be completely corrected by the adjustment of the model.
The EDM equipment and process specifications of the tooth profile cavity directly affect the surface quality of the cavity and the accuracy of the die profile. Hot forging die steel and high speed steel generally use 2 to 3 electrodes. The hard alloy tooth profile requires 4 to 5 electrodes to achieve higher precision of the tooth profile, and the electrode material also uses copper tungsten alloy.
In order to ensure high production efficiency and quality of the mold processing, the mold electrode needs to maintain the same positioning standard in the machining process and the EDM process of the machining center. At present, many companies and research institutes have adopted Swedish 3R fixtures or Swiss EROWA fixtures. The electrode is roughed before NC machining, the reference piece is fixed on the electrode blank, and then clamped on the reference seat of the machining center. The reference piece is moved to the reference seat of the EDM machine together with the electrode after the NC machining, ensuring The consistency of the benchmark.
In the process of electric spark forming tooth mold, the roughing electrode and the semi-finishing electrode should be well matched, and the size between the fine electrode should be properly matched, otherwise the production efficiency will be low, and the tooth surface quality of the mold is poor, sometimes due to the electrode. The excessive loss even affects the accuracy of the tooth shape, which ultimately affects the quality of the gear parts.
4. Subsequent machining of planetary gears and half shaft gears
(1) Machining of inner bore and spherical surface of planetary gears Precision forged planetary gears require drilling and spherical roughing and large-end chamfering, and grinding the inner and spherical surfaces after carburizing and quenching. Roughing and finishing should be based on the position of the toothed taper. Currently supported by three-ball spherical support, it is also supported by involute or linear toothed supports. The roughing is mainly supported by linear toothed supports, which can improve the supporting force. Finished spherical supports and toothed supports are also used.
(2) Subsequent processing of semi-axle gears Precision-forged half-shaft gears require drilling, roughing of inner bores, outer rounds, end faces and chamfers; finishing inner bores, outer circles, end faces; pull inner splines; carburizing and quenching; Grind the outer circle and the end face. The key positioning reference is the toothed cone. Positioning is similar to planetary gears.
5. Major quality problems that are prone to occur during the operation of planetary gears and half shaft gears
At present, the main quality problems that occur during the operation of planetary gears and half-shaft gears are planetary gears and half-shaft gears. The main reasons for the analysis from the gear angle are: the contact area of ​​the planetary gear and the semi-axle gear is small, the installation distance is excessively poor, the root cone angle is small, the big end chamfer is too large, and the size of the back cone is small. The contact area between the planetary gear and the half shaft gear is biased toward the top of the tooth, which makes the bending moment of the single tooth of the gear larger, which is directly related to the theoretical shape of the tooth profile of the planetary gear and the half shaft gear, the backlash and the coincidence degree during the meshing process. The installation gear is out of fluctuation and causes the individual teeth of the gear to bear a large load, which has a great relationship with the error of the circumferential section after the gear machining. In addition, the small taper angle causes the single tooth strength to be weakened; the large end chamfer is too large and the back cone size is small, which reduces the contact area of ​​the gear to a different extent. In addition to the influence of the shape and machining accuracy of the gear itself, the machining quality and assembly quality of the cross shaft, the differential case, the gasket and the like also have a negligible influence.
Analysis of the problem of toothing requires a comprehensive consideration of various factors and the identification of key causes to completely solve the problem. High-quality gears have strict requirements on accuracy and require strict control of the gear production process.
6. Conclusion
In recent years, planetary gears, semi-axle gears, precision forging and mold manufacturing technology have developed rapidly, from material control, heating to precision forging, to mold processing, and subsequent heat treatment and machining. progress. Future precision forged planetary gears and half shaft gears will develop toward higher precision, strength and less meshing noise.
The EDM equipment and process specifications of the tooth profile cavity directly affect the surface quality of the cavity and the accuracy of the die profile. Hot forging die steel and high speed steel generally use 2 to 3 electrodes. The hard alloy tooth profile requires 4 to 5 electrodes to achieve higher precision of the tooth profile, and the electrode material also uses copper tungsten alloy.
In order to ensure high production efficiency and quality of the mold processing, the mold electrode needs to maintain the same positioning standard in the machining process and the EDM process of the machining center. At present, many companies and research institutes have adopted Swedish 3R fixtures or Swiss EROWA fixtures. The electrode is roughed before NC machining, the reference piece is fixed on the electrode blank, and then clamped on the reference seat of the machining center. The reference piece is moved to the reference seat of the EDM machine together with the electrode after the NC machining, ensuring The consistency of the benchmark.
In the process of electric spark forming tooth mold, the roughing electrode and the semi-finishing electrode should be well matched, and the size between the fine electrode should be properly matched, otherwise the production efficiency will be low, and the tooth surface quality of the mold is poor, sometimes due to the electrode. The excessive loss even affects the accuracy of the tooth shape, which ultimately affects the quality of the gear parts.
4. Subsequent machining of planetary gears and half shaft gears
(1) Machining of inner bore and spherical surface of planetary gears Precision forged planetary gears require drilling and spherical roughing and large-end chamfering, and grinding the inner and spherical surfaces after carburizing and quenching. Roughing and finishing should be based on the position of the toothed taper. Currently supported by three-ball spherical support, it is also supported by involute or linear toothed supports. The roughing is mainly supported by linear toothed supports, which can improve the supporting force. Finished spherical supports and toothed supports are also used.
(2) Subsequent processing of semi-axle gears Precision-forged half-shaft gears require drilling, roughing of inner bores, outer rounds, end faces and chamfers; finishing inner bores, outer circles, end faces; pull inner splines; carburizing and quenching; Grind the outer circle and the end face. The key positioning reference is the toothed cone. Positioning is similar to planetary gears.
5. Major quality problems that are prone to occur during the operation of planetary gears and half shaft gears
At present, the main quality problems that occur during the operation of planetary gears and half-shaft gears are planetary gears and half-shaft gears. The main reasons for the analysis from the gear angle are: the contact area of ​​the planetary gear and the semi-axle gear is small, the installation distance is excessively poor, the root cone angle is small, the big end chamfer is too large, and the size of the back cone is small. The contact area between the planetary gear and the half shaft gear is biased toward the top of the tooth, which makes the bending moment of the single tooth of the gear larger, which is directly related to the theoretical shape of the tooth profile of the planetary gear and the half shaft gear, the backlash and the coincidence degree during the meshing process. The installation gear is out of fluctuation and causes the individual teeth of the gear to bear a large load, which has a great relationship with the error of the circumferential section after the gear machining. In addition, the small taper angle causes the single tooth strength to be weakened; the large end chamfer is too large and the back cone size is small, which reduces the contact area of ​​the gear to a different extent. In addition to the influence of the shape and machining accuracy of the gear itself, the machining quality and assembly quality of the cross shaft, the differential case, the gasket and the like also have a negligible influence.
Analysis of the problem of toothing requires a comprehensive consideration of various factors and the identification of key causes to completely solve the problem. High-quality gears have strict requirements on accuracy and require strict control of the gear production process.
6. Conclusion
In recent years, planetary gears, semi-axle gears, precision forging and mold manufacturing technology have developed rapidly, from material control, heating to precision forging, to mold processing, and subsequent heat treatment and machining. progress. Future precision forged planetary gears and half shaft gears will develop toward higher precision, strength and less meshing noise.
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- Magnesia cement uses in masonry construction is ancient. It was used primarily as a mortar component and stabilizer for soil bricks. Magnesia has also been identified in the Great Wall of China and other ancient landmarks. Roman cement is reported to have contained high levels of magnesia.
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