Grease leakage is one of the common faults of robots. The leakage will cause the harmonic reducer to lose oil and cut off oil, which will increase the wear of the gear meshing surface, which will lead to poor robot accuracy retention. More serious consequences may lead to robot accidents, resulting in economic loss to end users. At the same time, the leakage will pollute the environment, cause corrosion to the basic equipment, and also seriously affect the 6S construction of the factory. So what is the reason for the oil leakage of the harmonic reducer?
1. Pressure difference inside and outside the harmonic reducer
During the working process of the harmonic reducer, various internal friction pairs generate a lot of heat, which causes the internal temperature and pressure to increase, and the grease leaks from the gap under the action of the pressure difference. The higher the temperature rise inside the harmonic reducer, the greater the risk of leakage.
2. The design of the sealing structure is unreasonable
(1) The premise of the pumping effect of the oil seal is that the contact pressure peak is close to the oil side. When the pressure peak is close to the air side, the oil side pressure gradient is smaller than the air side pressure gradient, and the oil seal will leak.
(2) No static seal is designed.
(3) The roughness of the mating surface is too low.
3. Harmonic reducer oil seal failure
At high temperatures, grease can accelerate the dissolution of the rubber, resulting in early failure of the seal. Early wear and tear occurs.
4. Too much grease is filled.
Harmonic reducers are widely used in joint robots, collaborative robots, non-standard turntables, precision CNC turntable indexing equipment, woodworking engraving equipment and other industries. The following points should be paid attention to in the design:
1. About the tolerance fit at the location of the input end
(1) If the size of the reducer boss is h7, the flange hole tolerance is generally +0.15 to +0.1;
(2) If the size of the reducer boss is H7, the flange hole tolerance is generally -0.1 to -0.15.
2. Pay attention to interference and avoidance
In the design, attention should be paid to the avoidance of the flex wheel book and the steel wheel book to prevent interference caused by the deformation of the flex wheel during operation.
3. Installation position of the wave generator
The mounting dimensions of the wave generator are the basis for designing the dimension chain.
4. About sealing
(1) The O-groove has been opened on the drum side of the harmonic reducer, and the O-groove needs to be opened according to the size recommended in the sample book on the flexible pulley side.
(2) O-slots need to be opened according to the recommended size in the catalog.
(3) Determine whether the motor has a skeleton oil seal to prevent grease from entering the motor.
(4) Add an O-slot between the motor and the input flange.
(5) The O-rings on the drum side and the flexible wheel side of the harmonic reducer are packaged in the packaging box with the reducer according to the size.