The size and position of the unbalanced dimensions of the machine spindle are always random. This will result in unbalanced vibration of the machine tool spindle, which has the same characteristics as the rotation of the shaft and it is easy to identify. An effective way to eliminate this vibration is to correct the spindle on the low-speed balancing machine, that is, to select the two calibration balance planes in the unbalanced orientation of the spindle, and to adjust the quality to achieve a balanced purpose. According to the dynamic balance standard, the specified speed within the first critical speed of the shaft is called the rigid rotor. The balance method known as the rigid shaft balance. Higher than the first critical speed Rotary shaft dynamic balance called flexible rotor or flexible shaft balance, such as turbine shaft balance. Machine tool spindle are generally rigid shaft balance. Rigid is characterized by a balance in a certain speed, to ensure that the spindle at all working speed balance. But the flexible shaft in the entire speed range, including several critical speed, the imbalance caused by the vibration and interference is a minimum. At present, the use of dynamic balancing machine can reduce the amount of unbalanced to a very low limitation, but too little to improve the accuracy requirements are not economical. The range of the unbalance of the spindles with the different types and different requirements should be reduced to what extent. We introduces the dynamic balance of machine tool spindle and its balance precision selection.
The purpose of the spindle balance is mainly determined by the machine characteristics and machining accuracy. Any type of spindle or its components must be balanced before the balance to determine the level of accuracy. For some machine tools, the balance is a process of spindle production. The dynamic balance through the spindle vibration, bearing vibration or bearing reaction has reduced to a certain range. Balancing the spindle is not only on the balancing device but also in working conditions. Therefore, we must strictly abide by the provisions of dynamic balance standards to ensure the balance of shaft accuracy. The dynamic balance of the rigid rotor standard provides that the accuracy of the rotation axis level is mainly for the balance body, such as the spindle or its components. According to the production situation, the spindle, rotor, fan, nut and other parts combine a spindle, and then move the balance. The unbalanced vibration of the machine tool spindle is affected by many factors. In addition to the spindle itself, such as the quality of the machine body and the foundation, the stiffness of the bearing, the speed of operation and the resonance frequency are close to the damping. Therefore, a machine tool spindle dynamic balance, the size of the remaining unbalance to determine the size has to consider a variety of factors.
Since each spindle always has a certain initial imbalance. It is first necessary to estimate the initial unbalance of the shaft. When the initial unbalance value exceeds a certain value, if the two calibration plane balance is in the high-speed range of operation, it may not be a reliable balance. Therefore, the initial unbalance amount is controlled in the design, manufacture and assembly of the spindle by calculating a limit value for each type of shaft in advance, thereby limiting it to this.