The imbalance measured by centrifugal fan in the balance process is eliminated by the calibration operation after measurement. The balance weight is generally added to the lighter part of the rotor or the heavier part is removed. In addition, a few rotors, such as fan blades, can be balanced by bending the blades and changing the shape of the rotors. As a check method of centrifugal fan imbalance, common machining methods can be adopted. One is to configure the correction block in the opposite direction of imbalance, sometimes the balance is achieved by welding method. The convex welding method is generally used. The plate welding sheet used has a certain width and thickness, and the length depends on the size of the unbalanced amount. General centrifugal fan impeller also adopts welding method for counterweight balance. Balance the rotor of small motor, sometimes by tin welding. Check the weight of tin welding according to the size of imbalance. Sometimes rivets are used as balance blocks. Compared with other methods such as tin welding, this method can be corrected accurately. Blade, turbine, clutch friction plate can be used in this method. The screw holes are arranged at equal distance in the circumference of a certain radius of the centrifugal fan rotor, and the screws of different lengths are screwed in according to the imbalance. The selected correction weight blocks are suitable for the shape and structure of the rotor, and several balance weight blocks are prepared according to the size of the unbalanced amount, so that the operation is convenient. Another is to weigh in the unbalanced direction of the centrifugal fan, generally using the drill bit drilling on the rotor to eliminate the imbalance method; smooth surface rotor, such as blade, pump impeller, centrifugal separator rotor and drum equal, generally using grinding method to correct; turbine and large gear, sometimes using this method to correct.