Reducing bearing noise is an urgent problem that the bearing industry needs to solve in improving bearing quality. The main factor affecting the bearing noise is the waviness of the bearing raceway surface and the surface of the steel ball. The waviness is caused by vibration during the grinding process. Therefore, it is very necessary to study the relationship between the vibration and the waviness and the causes of the vibration. The relationship between vibration and waviness There are many reasons for affecting the waviness, mainly depending on the magnitude of the vibration during the grinding process. The greater the vibration force, the greater the amplitude. As the amplitude increases, the waviness value of the waviness also increases, and the waviness value is proportional to the amplitude of the vibrating body. In order to find out the cause of the vibration, first measure the number of corrugations, and then you can calculate which type of vibrating body is. The relationship between them is:

N vibrationu003daN workpiece

Where N vibration—the number of revolutions per minute of the vibrating body N workpiece—the number of revolutions per minute of the workpiece a—the workpiece is in a The number of corrugations on the circle

Causes and elimination methods of vibration In the grinding process, the grinder mainly produces forced vibration, self-excited vibration and free vibration. Forced vibration accounts for more than 60%, self-excited vibration accounts for about 30%, and the rest is free vibration. 1. Forced vibration There are many reasons for forced vibration, but because the vibration frequency caused by forced vibration is often equal to or double the frequency of the vibrating body itself, it is easy to find the vibration source and eliminate it. 1. Caused by the imbalance of the grinding wheel (1) The grinding wheel should be statically balanced before rough repair, and then statically balanced again after rough repair, and then the grinding wheel should be finely repaired. (2) When installing the grinding wheel, care should be taken to make the flange of the grinding wheel and the taper hole vertical, so that the taper hole and the taper surface of the spindle are in good contact, and the same thickness of paper should be placed on both sides of the grinding wheel to avoid the grinding wheel due to poor installation. unbalanced. (3) After stopping grinding and turning off the coolant, the grinding wheel should continue to idle for 5-7 minutes, and the excess coolant on the grinding wheel should be removed by centrifugal force. Otherwise, after the machine tool stops for a certain period of time, the remaining coolant will solidify on the lower part of the grinding wheel, and when the machine tool is restarted, the grinding wheel will be unbalanced. (4) Because the internal structure of the grinding wheel is uneven, even if the original well-balanced grinding wheel will produce new imbalances during use, it is best to use an automatic balancing device during the grinding process. 2. During the grinding process of the grinding wheel due to the different bonding strength of the grinding wheel, the bonding strength of each grinding wheel is different, and the speed of the abrasive grains falling off is also different. For the part with high bonding strength, the abrasive grains are not easy to fall off. Local passivation. The grinding wheel itself naturally forms a corrugated state, which also causes vibration during the grinding process. 3. Influenced by the vibration of the motor (1) The imbalance of the rotor, pulley and other rotating parts of the motor will also cause vibration, so the dynamic balance must be carefully balanced, and it is best to reduce the amplitude of the motor to about 5μ. (2) The poor quality of the rolling bearing on the motor will cause vibration, so the ordinary bearing should be replaced with a precision bearing. (3) Motors that have already taken measures still vibrate. Therefore, hard rubber or vibration damping device should be used to isolate it at the machine tool installation. 4. Unbalanced parts caused by high-speed rotation The main reasons for unbalanced parts caused by high-speed rotation are: (1) The material density of the parts is not uniform, and the quality of the casting blank is not good, such as impurities and pores on the pulley; (2) Parts Irregular shapes, such as shoulders, holes, keyways and fastening parts, etc.; (3) The center of gravity of the parts that are fixed and rotated together is not on the center of rotation.

Due to the inertial force caused by the unbalance, the influence on the vibration of the machine tool is very large, and the unbalanced eccentric force is proportional to the square of the angular velocity. In order to eliminate the imbalance of the rotating parts, it is not only carefully designed and manufactured, but also carefully balanced in use. There are two general balancing methods: one is static balance, which is suitable for parts whose length and diameter ratio (L/D) is less than 3; the other is dynamic balance, which is suitable for parts whose length and diameter ratio is greater than 3. 5. Caused by rotating parts (1) The gear accuracy is not good, such as unequal tooth pitch, involute tooth profile error and pitch circle runout error. The vibration generated by the above reasons forms complex vibration. In order to eliminate this vibration, it is necessary to improve the manufacturing precision of gears, especially gears with high peripheral speed. (2) The belt should not be adjusted too tightly. It is best to use leather, silk and glued jointless flat leather, because they have a good vibration damping effect, which is one tenth of the vibration of the V-belt or less. When choosing a V-belt, attention should be paid to its quality, such as thickness, width, and flexibility. The pulley should be unloaded as far as possible to reduce the deflection of the main shaft. (3) The precision of the bearing used for the rotating spindle is not high, and the vibration is caused by the difference in the wall thickness of the raceway, the waviness, the out-of-roundness and the size difference of the rolling elements. Therefore, high-precision bearings should be selected.