Elimination Of Burns In Gear Grinding

- May 28, 2019-

In order to reduce the surface grinding problem, the most important thing is to reduce the generation of grinding heat from the source, while accelerating the grinding heat emission. Through a series of analysis of burn factors, it is found that the following measures can be taken to reduce the impact of grinding heat on gear friction.


4.1 grinding wheel


In the process of grinding wheel selection, because of the soft hardness of rough grinding wheel, it is easy to produce grinding surface, blockage will cause greater obstacles, and a large number of heat will be generated in the process of grinding. Fine grinding wheels with higher hardness must be used in the process of grinding, and the grinding surface needs to be smooth, and finally the size of the grinding wheel must be guaranteed to be qualified. The grinding hardness of diamond is generally relatively large. Because of the excessive hardness and strength, the grinding conditions have been significantly improved, which weakens the grinding force on the surface. In addition, if the coefficient of friction is low, there will be no more friction without lubricant, so there will be no excessive burns. At present, CBN grinding wheel is widely used because of its good thermal stability, low grinding temperature, good hardness and strength. Small grinding force can greatly improve the surface quality. In addition, some rubber and resin can also greatly improve the grinding conditions. For some reasons, in the process of increasing the cutting force, it will produce greater elastic yield force, which will continuously reduce the depth of cutting and effectively reduce the occurrence of burns. The balance treatment of grinding wheel must be in place, so as to maintain a better state in the process of later balance. The grinding wheel must be kept in a sharp working state at all times. There are many factors that will affect the operation of the wheel, the type and purity of the final materials and so on will have a greater impact on it. The diamond support of grinding wheel should be paid attention to in the early fixing process. If the surface of the diamond is worn by 0.5-0.6 mm, it indicates that it has been passivated and needs to be replaced.


4.2 Grinding Conditions


In the process of generating heat, the grinding wheel generates heat proportionally in unit time, which can effectively avoid grinding damage, appropriately reduce the cutting depth, and reduce the power of power generation, thus ensuring that the rough grinding is not more than 0.03-0.04 mm, while the fine grinding is not more than 0.01-0.02 mm. The selection of grinding allowance should be determined according to the specific conditions, and the grinding burn should be reduced as far as possible in the case of increasing productivity. Because of the large grinding allowance in rough grinding and one-time firing, it is not easy to eliminate the defects in fine grinding, and the previous rough grinding feeds are easy to be ignored by operators. Therefore, after quenching, according to the gear surface to find the correct processing positioning benchmark, so that the edge of the tooth surface is evenly distributed, and find the highest point of the tooth profile, the grinding wheel in this place began to feed grinding.


4.3 cutting fluid


Cooling control is a key factor in the operation of gear grinding. Cooling must be complete and sufficient. Coolant must also flow into the region. In most cases, flow rate should be controlled at 40-45L/min, so that complete cooling can be achieved. Pressure is generally controlled at 0.8-1.2N/mm2, and surface chips can be better washed out. When the coolant is clean enough, the dirty particles in the coolant can be removed. The carrying capacity of the coolant must be large enough to prevent excessive bubbles. To prevent the cooling fluid from changing the temperature too quickly, the volume of the cooling system and the room temperature of the working room can be controlled well, but in some special storage conditions, the radiator is still needed to work.


Carbon Concentration in 4.4 Carburized Layer


With the increase of surface carbon concentration, grinding performance will be reduced, so it is appropriate to control the surface carbon concentration between 0.2% and 0.9%. The carbon content of retained austenite is generally within 32%, carbides need to be evenly distributed on the surface, while ensuring that the average diameter of the particles is less than 1 micron; carbides are generally spherical or granular distribution, prohibiting the production of network or corner carbides. It is necessary to strictly deal with the thermal technology of the surface and strictly manage the carbon content of the surface, so as to minimize the malformation and pathological changes of the hot surface. In order to select the most suitable grinding fluid, the grinding specification should be well regulated. In gear grinding process, cooling is a key technology. Cooling must be fully effective, coolant must reach the prescribed position, pressure at least needs to wash off the chips on the grinding wheel, so as to conduct proper filtration.


After the above series of improvement measures, in the subsequent gear grinding process, there is basically no grinding burns. In the process of processing the same gear, the original time is maintained at about 12 hours, now it only takes 10 hours on average, and the quality is improved by 17%.


Gear is one of the main parts of industrial equipment at present. Compared with the common carburized and quenched gears, the contact stress of gears has been greatly improved after carburizing and quenching treatment. However, there are still some shortcomings and common problems in this process. The most common one is surface abrasion. The quality of the gears used will suffer serious losses, so we still need to improve it. Conduct research and management.