The technological process represents the technological level of gear processing. It should be carried out according to the relevant standards in combination with the processing plan. Each process should be strictly controlled, and the operation should be carried out according to the operating standards to improve the processing safety. The gear processing process includes: blank production, normalizing, cutting, gear hobbing and gear shaping, gear shaving, heat treatment, grinding and trimming. Each of the above processes is a very mature technology. As long as the staff operates in accordance with the standardization, and the tools and equipment processed are in normal operation, the final gear meeting the processing requirements will be obtained, and there will be no problems in quality. If each process can be further optimized according to the gear working environment and existing equipment conditions, more efficient and high-quality products will be obtained.
1. Forging blank
In order to further improve the performance and quality of gears, forged parts should be selected as blanks. Therefore, most gear processing plants in China use hot die forging to produce blanks, which can maximize the mechanical properties of the blanks, so as to obtain gears with excellent performance. In forging process, it is not only more convenient to make blank by cross wedge rolling, but also greatly improve the processing accuracy and efficiency. This technology is widely used in batch production.
2. Normalizing
During the forging process, the blank will leave internal stress in the material, resulting in banded structure, coarse grain and segregation and other defects in the blank, making the material hardness too high. Therefore, in order to improve the defects left by forging, it is necessary to remove the internal stress of the material and reduce the deformation of the material, so as to prepare for the subsequent process, facilitate the more effective processing of the material and ensure the quality of the gear. However, the normalizing process is easy to be affected by external factors during the operation process, mainly including the operators and the environment. Because the operators and the processing environment are difficult to effectively control the cooling speed of the parts, it is easy to cause uneven cooling, which will make the formation of the internal fabric of the parts incomplete, easy to bring difficulties to the subsequent machining, and thus affect the quality of the workpiece processing. In view of this problem, many manufacturers now adopt the isothermal normalizing method to fundamentally solve this problem and greatly improve the processing quality of the workpiece.
3.Cutting
Cutting is to use lathe, milling machine or CNC machine tool to process gears, mainly to finish some machining on gears, such as end faces and holes. During cutting, the corresponding tool needs to be selected according to different processing procedures, and the workpiece needs to be positioned and clamped according to different positioning benchmarks, which can ensure the machining accuracy and quality of the workpiece. If NC machine tools are used for cutting, multiple cutting can be completed with only one clamping, and multiple features can be processed at the same time. Compared with traditional machine tools, this not only greatly improves the machining efficiency, but also further improves the machining accuracy.
Although machining can meet the requirements of gear machining, they all need cutting oil or coolant in the process of machining, which will not only pollute the environment, but also pose a threat to the health of operators. On the other hand, the use of cutting oil or coolant is quite large. The purchase of cutting oil, the design of cooling system and the treatment of waste oil will bring high economic costs. Therefore, at present, a dry cutting technology has begun to receive attention. Dry cutting technology is to remove the use of coolant on the basis of the original cutting equipment, and add a cooling system that does not need coolant, which greatly reduces the processing cost. Dry cutting technology mainly includes spiral bevel gear dry cutting technology, gear shaping dry cutting technology, gear hobbing dry cutting technology, etc. This kind of technology has been widely used in foreign countries. Compared with the use of cutting oil, the efficiency of dry cutting technology has more than doubled, and has a significant effect on reducing processing costs.
4. Gear hobbing and gear shaping
Gear hobbing and gear shaping are mainly used to process the gear teeth. According to the different processing principles, they can be divided into the generating method and the generating method. Both methods can meet the processing accuracy requirements of the gear teeth, but the disadvantage is that the processing efficiency is low. In case of mass production, it requires multiple equipment to operate at the same time, and the processing cost is high. In recent years, many manufacturers have begun to introduce coating protection technology, coating new materials on the props of gear shaping and gear hobbing, enhancing the hardness, wear resistance and corrosion resistance of the props, effectively improving the service life of the tool while reducing the processing cost, and also improving the processing efficiency of gear hobbing and gear hobbing, and significantly improving the gear processing quality.
5. Shaving
Gear shaving is a high-precision machining process, which is mainly used to finish the machined teeth, including tooth shape correction and reduction of tooth orientation deviation to ensure the machining requirements of gear surface roughness. This process has good processing efficiency, and the precision and quality of the processed gears are also very good, especially suitable for the production of medium or large batches of parts. At present, this technology is relatively mature in China, and it is almost adopted in the gear finishing stage. The working principle of gear shaving: firstly, the gear shaving cutter is used to mesh with the spiral gear pair with no side clearance of the workpiece, and then according to the difference in the direction and speed of the two at the contact point, the side of the gear to be machined will slide along the side of the gear shaving cutter, and the tooth side of the gear wheel will be finely cut by the chip cutter to complete the shaving process.
6. Heat treatment
The final heat treatment is an important link to determine the quality of the gear. The control of the uniformity of temperature and cooling speed will affect the hardness and deformation of the gear. In particular, the performance of gears requires carburizing and quenching at the heat treatment stage, so as to obtain better mechanical properties. However, if the temperature stability is not well controlled during carburizing and quenching, it is likely to cause serious deformation of gears. Therefore, it is necessary to improve the carburizing and quenching equipment and optimize the heat treatment process, so as to master the change law of temperature and deformation during the heat treatment process, and use reverse deformation Pre-expansion of the shrinkage end and other methods can further improve the qualification rate of the gear heat treatment to ensure that the gear quality reaches the standard.
7. Grinding
The workpiece after heat treatment will have different degrees of deformation, so it is necessary to use grinding to finish it. The main purpose is to reduce the dimensional accuracy and form and position deviation of the gear end face, hole diameter and other features, so as to ensure the gear processing accuracy and further improve the processing quality. Because of the high precision requirements of the grinding process, most manufacturers use CNC gear grinding machines to reduce the processing error of manual operation, and at the same time greatly improve the production efficiency. There are also significant advantages in the processing accuracy. Now, CNC gear grinding machines have been widely used in some large mechanical equipment gear manufacturers in China.
8. Gear finishing
Dressing is the last step of the machining process, and also an inspection of the quality of the machined workpiece. Through dressing, the burr on the gear during operation can be well found, so as to avoid noise or gear meshing deviation during actual assembly and use, which will affect the stability of the mechanical equipment operation, and ensure the gear quality is qualified. The gear trimming process will be carried out in some gearboxes, mainly by observing the meshing condition of the gear teeth, checking whether there is meshing deviation and abnormal noise, so as to judge whether there is burr on the gear and clean it.