Some large-scale fan motor production plants in Guangdong Province have such a situation. A batch of motor assemblies have not experienced abnormal phenomena during the trial operation before leaving the factory. Some of the products were shipped outside the province, and some even exported to the Middle East. However, when the merchants received the goods, they found that the motor rotation noise was abnormally increased. After the motor was disassembled, the motor bearings were found to be seriously rusted, except for the inner diameter and the end face, which were mainly rusted. The rust position is at the contact point between the steel ball and the raceway. Although the rusting procedures are different, it affects the normal operation of the motor, and the merchant returns it. Such accidents not only affected the reputation of the motor factory, but also hindered the normal operation of the motor factory.
The motor manufacturer believes that there is a problem in the bearing quality and anti-rust treatment produced by the bearing factory. They found our bearing product quality inspection station, required to check the quality of the bearing, and assist them to solve the problem of rust of the motor bearing.
2 Motor bearing sample corrosion accident characteristics
Through the production process, production environment, composition of insulating varnish used, grease composition, assembly process, packaging materials, warehouse storage and related production and sales of motor parts and bearing production plants On-site investigation found that the rust accident has the following characteristics:
(1) It mainly occurs in household appliances and office machinery such as ventilation fans and cooling fan motors. The motors used in these machines are mostly several watts to hundreds of watts, and are basically fully enclosed small motors.
(2) The packaged single motor is not found to be abnormal after the trial run of the finished product, and noise increase occurs when it is used for several months after storage. After the motor was disassembled, it was found that the noise was caused by the rust inside the bearing.
(3) Corrosion of the motor bearing is during the manufacturing process or during storage in the warehouse, which is just the highest temperature and humidity in March and April of each year.
(4) The bearings required by the motor factory are generally purchased directly from the bearing factory. The motor factory buys back the bearing that has been rust-proofed by the bearing factory, injects the grease by itself, and then installs it on the rotor of the motor. Most of the grease used for bearings is added to the lithium base oil. It is easy to cause paint rust when using solvent-based paint.
(5) The inside of the bearing is sometimes more serious than the external corrosion. This rust is related to the type and relative humidity of the grease. The ester oil is in the medium humidity (70% RH), and the grease is rusted. Corrosion caused by moisture, rust easily on the outer surface of bearings that are not coated with grease.
(6) Grease has a special paint odor because the grease has deteriorated.
(7) The corrosion of the bearing has obvious directionality, that is, the side of the bearing facing the rotor side of the motor is mostly rusted, and inside the bearing, the surface of the raceway near the rotor and the cage are often rusted.
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