What are the effects of rotor imbalance on motor quality? We will analyze the vibration and noise problems caused by mechanical imbalance of the rotor.
01 Causes of rotor imbalance vibration: residual imbalance during manufacturing, large amounts of dust attached during long-term operation, shaft bending caused by thermal stress during operation, unbalanced load caused by thermal displacement of rotor accessories, deformation or eccentricity caused by centrifugal force of rotor accessories, shaft bending caused by external forces (belts, gears, poor direct connection, etc.), shaft bending caused by poor bearing installation (axis accuracy or locking) or internal deformation of bearings.
02 How to suppress rotor imbalance: maintain within the allowable imbalance, improve the excessive tight fit between the shaft and the core, anisotropy of thermal expansion, and design improvement. Improvement of strength design or assembly, correction of shaft strength design, change of shaft coupling type and correction of direct connection center, and prevention of deviation between the bearing end face and the shaft attachment or locking nut.
03 Causes of abnormal vibration and noise of bearings: damage inside the bearing, abnormal axial vibration of the bearing, excitation of the vibration system composed of axial spring constant and rotor mass; poor lubrication and bearing clearance of cylindrical rolling bearings or large-diameter high-speed ball bearings.
04 Bearing replacement: appropriate axial spring preload to change the bearing clearance, choose soft grease or grease with excellent low-temperature performance, and the residual clearance becomes smaller (pay attention to the temperature rise problem).
05 Rotor dynamic balancing correction method: After the dynamic balancing measurement of the rotor of the dynamic balancing machine, the rotor can be balanced by weighting and deweighting methods as needed: the so-called weighting method matches the correction weight block in the opposite direction of the imbalance. Common methods include welding, soldering, riveting, screwing, adding weight blocks, etc. The deweighting method is to remove a certain amount of weight in the unbalanced direction. Common methods include: boring, drilling, chiseling, milling, grinding, etc.