Cute Bath Sponge,Custom Shape Bath Sponge,Round Bath Sponge,Body Cleaning Sponges Liya Beauty Accessories Co., Ltd. , http://www.chinapowderpuff.com
2 Comparison of shaving process and grinding process
There are many reasons why the gear shaving process and the gear grinding process coexist. Due to the length of the article, only the following simple analysis and comparison:
(1) The reasons for the noise of the transmission caused by the reduction of transmission noise are: 1 the accuracy of the gear (including tooth shape, tooth direction, pitch, etc.); 2 the accuracy of the device (the accuracy of the hole system, the center distance and its variation) ); 3 structure of the gearbox (rigidity and deformation of the transmission).
Gear manufacturers have long relied on gear grinding to improve the quality of the entire gear. However, although the grinding process is almost perfect in ensuring the accuracy of gear machining, it is unfortunate that its processing cost and investment cost are high, and it is difficult to obtain high-quality gears at a lower cost. On the other hand, high-precision gears do not necessarily guarantee a reduction in transmission noise.
With the development of CNC shaving technology, with the help of advanced CNC shaving cutters, we can now complete the grinding of various shaving cutters in dozens of minutes. At the same time, the current shaving machine can control all movements through the program. That is to say, at present we have the ability to achieve shaving processing that was not possible a few years ago. Although the quality of some gears after heat treatment cannot be fully controlled (quenching will cause deformation of some gears, especially gears with uneven structure, which are common in vehicles and tractors), we control the shaving accuracy to 5 And the anti-deformation measures of the shaving teeth can be used to minimize the heat treatment deformation of the automobile gears, especially those used in the automatic transmission, thereby stabilizing the finished product size.
The advanced shaving process can improve the tooth accuracy by 2-3 grades (DIN standard), improve the tooth profile accuracy by 2-3 grades (DIN standard), and increase the pitch accuracy by 1-2 grades (DIN). Standard), the surface roughness of the shaving surface is close to the surface roughness of the grinding (Ra 0.4-0.6μm), and the gear with 5 precision (DIN3962) is obtained through careful shaving and shaving (the inherent characteristics of the gear should be consistent with The use of shaving processing).
In order to reduce the meshing noise of the gear, we usually consider the theoretical standard and actual situation of the tooth profile and the tooth direction. In the production of shaving, it is necessary to check the meshing condition of the meshing gears, and sometimes special shaping of the tooth shape is required to reduce the transmission noise. Now with a full CNC shaving cutter, this modification is easy to achieve.
(2) Elimination or reduction of heat treatment deformation In the medium and large-scale production, by analyzing the deformation of the gear tooth shape and the tooth direction caused by the heat treatment, the compensation amount (anti-deformation) can be compensated during the shaving process, Achieve the purpose of eliminating or reducing heat treatment deformation.
Since the theoretical tooth direction is different from the actual measured tooth direction, the ideal gear tooth accuracy is achieved by controlling the shaving parameters of the shaving process and various aspects of the special shaving cutter, and at the same time reducing the transmission noise and achieving low utilization. The cost of the shaving process produces the same quality gears as the high-cost grinding process, meeting the quality requirements of various shifting gears.
(3) Advantages of the shaving process of CNC machine tools 1 Various tooth profiles and tooth orientations can be completed to obtain gears with high finishing surface and good tooth shape;
2 As a widely used gear processing technology, 2 shaving has the characteristics of flexible and rapid processing, high production efficiency and high automation. The shaving machine can be inserted into the automatic production line; the tool can be used to its fullest;
3 low processing costs (including machine depreciation and tool costs), low maintenance costs, can reduce costs.
(4) The scope of application of the gear shaving process According to the gear standard DIN3962, the main application range of the shaving process is:
1DIN7-8 grade: scope of use: industrial vehicles, agricultural machinery, tractors and machine gears with low quality requirements; automotive gearboxes, low-speed reducers, etc.;
2DIN6 grade: Firstly, the grade 5 precision is achieved by shaving, and it is easy to achieve 6 grades after heat treatment. Scope of application: gearboxes for various vehicles (including cars with higher quality requirements), gears for industrial vehicles, machine tools and reducers. This is the most widely used level of accuracy;
3DIN5 grade: After the shaving process, the control of the heat treatment deformation ensures that the precision of the finished gear after heat treatment does not change. Scope of use: aircraft gear trains, high quality cars, buses, trucks, gauges, etc.
In addition, some gears cannot be ground because they cannot be ground. For example, small gears connected to large gears or gears with shoulders, synchronizers and other components. For example, the two-axis shaving of the gearbox, the shaved gear is mainly used for the transmission of the vehicle. Since the two-speed gear cannot be ground, it is necessary to shave (generally, the gear processed with the gear cutter cannot be ground).
Of course, for some gear trains that transmit a very large torque (such as heavy trucks, etc.), although the final required precision can be obtained by the shaving process, it is currently shaped and ground. This is because the forming of the gear makes the root of the gear smoothly transition, making the gear stronger, and the risk of toothing in the transmission is greatly reduced, so the larger modulus (4-8mm) gear is usually ground. In addition, gears above DIN4 must be ground.
In recent years, a rapid development of the new process - the internal honing process has promoted the large-scale adoption of the gear shaving process. Because the CBN grinding wheel honing process does not remove a lot of metal materials, the ç© front gear error of the honing gear can not be very large, and the price of the CBN grinding wheel is very expensive. If the gear deformation caused by heat treatment is very large, in order to facilitate the removal of the material, it should be used before the heat treatment. The shaving process with deformation compensation removes more margin and effectively reduces heat treatment deformation, which will contribute to the honing process after heat treatment.
(5) In the same example, the planetary gears for automatic shifting are processed in the same way. The grinding process can obtain the 5-stage (DIN standard) gear in about one minute; and the processing time required to obtain the same grade of gears by shaving is higher than that of the general grinding. The reduction is reduced by 13-15s. In addition, shaving requires only one machine, while grinding requires at least three machines, so the cost of grinding is twice that of shaving.
In view of the above, all costs and profits should be estimated first before selecting the gear machining process.
3 progress in shaving technology
(1) Improvement of the shaver The current shaving cutter does not make much progress like other tools used in the gear processing industry (for example, the hob is first introduced by introducing TiN, TiAlN, TiCN coatings, and allows cutting speeds of nearly 200 m/ Min's new high-speed steel material has achieved good results). When shaving, there is not much material to be cut, and the cutting speed is not high, so the pressure of the cutting edge of the tool during processing is not large. Despite this, the experts still feel the need to make the shaving edge sharper in order to reduce losses. The manufacturing process of the shaver has not changed, and the coating process does not have a great effect on the shaving cutter (because the side surface of the shaving cutter chip pocket is no longer processed after heat treatment, the surface is rough, and the TiN coating is difficult to attach to The side of the groove), so the experts turned their attention to improving the side roughness of the shaving groove. The CNC carding machine developed now has greatly changed the surface roughness of the processing surface of the shaving cutter chip pocket. In addition, researchers in Japan have conducted experiments on the cryogenic treatment of liquefied nitrogen after heat treatment of tool materials. In this way, the characteristics of the shaver material are changed, the average service life is extended, and the performance of the shaver is improved.
On the other hand, it is worth emphasizing that modern CNC shaving cutters achieve flexibility, precision and speed. These three main features have resulted in significant improvements in the accuracy of the gears processed using the shaving process. This is another reason why the shaving process has not been replaced by a grinding process.
(2) Development of shaving machine tools and processes In the past 50 years, the shaving machine tools have been continuously developed, and the shaving technology has been increasingly perfected. The latest CNC shaving machines perform a wide range of shaving procedures (including axial shaving, diagonal shaving, tangential shaving and radial shaving, etc.), as well as the shaving process on the same gear Among them, one can be transferred from one shaving method to another. These special processes are implemented under the direct supervision and control of the numerical control (NC). The advantage of CNC shaving is that it can control various parameters such as cutting speed, radial feed and stroke during the shaving process. During the shaving process, the parameters such as feed rate, cutting speed and stroke length can be changed. It is more convenient for us to choose different processing conditions. In the specific shaving process, in addition to the above standard shaving method, "Progressive Diagonal Cycle", "Disjointed Diagonal Cycle", "Mixed Shaving" can also be selected. Specific processes such as "Mixed Cycle" and "Twin Linked Cycle".
1 When the progressive diagonal shaving is diagonally shaved, the drum shape that may occur in the tooth direction is achieved by the swing of the table around the center. This action is achieved by swinging around the x-axis and is done under computer control. The coordinated movement of the three axes x, y, w can result in a drum shape or a taper angle on both sides of the gear. If the drum is quite large, the material to be cut is excessive, and the gear is subjected to multiple oscillating shaving, the number of swings of the x-axis can be set so that the materials at both ends are progressively cut.
2 Hybrid shaving It is well known that radial shaving takes less time than tangential shaving, but the machined surface is rough. The solution is to cut a large amount of margin by radial cutting and then perform axial or diagonal shaving for finishing. With this hybrid shaving method, uniformity in shortening the shaving time and obtaining a good shaving surface quality can be achieved.
3 Discontinuous diagonal shaving cycle, double shaving using two special processes of discontinuous diagonal shaving cycle and double shaving can get different tooth direction correction. For example, the machining process is divided into three sections by discontinuous diagonal shaving, and different drum and taper requirements are formulated according to the specific processing standards of each section. Therefore, it is easier to obtain the tooth orientation correction of the special and asymmetrical convex shape, so that the anti-deformation tooth shape corresponding to the deformation which may occur after quenching can be processed, the meshing condition of the gear is changed, and the noise of the gear meshing is reduced.
1 Introduction <br> <br> As we all know, shaving machining and grinding are two different methods of finishing gear. Shaving is performed prior to heat treatment (this is also the reason for limited shaving), and grinding is performed after heat treatment. In recent years, with the continuous improvement of machining precision, the continuous improvement of CNC machine tools and the rapid development of processing software, gear finishing technology has been continuously developed, gear grinding precision, efficiency and various functions have reached a very high level. . Thanks to the use of new ceramics and CBN grinding wheels, both form grinding and grinding have been greatly improved. It has been argued that after a few years, the shaving process will be almost completely replaced by grinding, because there are indeed many In the past, gears that were machined with shaving were now replaced with gear grinding. However, people's expectations, in the global gear production, shaving processing is still the most important means of gear finishing.