Crossed roller bearings are composed of two major types, cross cylindrical roller bearings and cross tapered roller bearings. Crossed roller bearings have a long history of application, but only in recent years. Entering the public's horizon, it is widely used because of its uniqueness and superiority with other bearings. There are some problems with the installation of cross-roller bearings, such as lubrication, installation, cleaning, etc. Today, I would like to explain to you, I hope to help everyone.
First, preparation before installation
1, choose grease
Lubrication has an important impact on the operation and life of crossed roller bearings. Here is a brief overview of the general principles of grease selection. Grease is made of base oil, thickener and additives. The greases of different types and different types have different performances. The allowable rotation limits are different. Be careful when selecting. The performance of the grease is mainly determined by the base oil. The base oil of low viscosity is suitable for low temperature, high speed and high viscosity for high temperature and high load. The thickener is also related to the lubricating properties, and the water resistance of the thickener determines the water resistance of the grease. In principle, different greases cannot be mixed, and even greases of the same thickener may have a bad influence on each other due to the different additives.
2. Cleaning before bearing installation
The surface of the bearing is coated with anti-rust oil. You must clean it with clean gasoline or kerosene, and then apply it with clean high-quality or high-speed high-temperature grease. The effect of cleanliness on rolling bearing life and vibration noise is very large. But we have to remind you that closed bearings do not need to be cleaned and refueled.
Second, the bearing installation
1. Thoroughly clean the spindle, housing or other mounting parts to remove oil or impurities and confirm if there are burrs or burrs.
2. Install the crossed roller bearing into the shaft or housing: Because it is a thin-walled bearing, it is easy to tilt when loading. In order to prevent this phenomenon, please keep it level, evenly tap with a plastic hammer, and carefully insert the crossed roller bearing into the bearing housing or the shaft until the sound is confirmed by the sound. Do not directly hammer the cross roller bearing surface and the non-stress surface. The bearing should be evenly stressed by the clamp, sleeve or other installation tools (tooling). Do not install by the rolling element transmission force. If the mounting surface is coated with oil, it will make the installation smoother. If the interference is large, the bearing should be placed in mineral oil and heated to 80~90 °C and installed as soon as possible. Strictly control the oil temperature not to exceed 100 °C to prevent the tempering from lowering the hardness and affecting the dimensional recovery. When disassembling is difficult, it is recommended that you use the disassembly tool to pull outward while carefully pouring hot oil onto the inner ring. The heat will cause the inner ring of the rolling bearing to expand, making it easier to fall off.
3. Place the fixing flange on the cross roller bearing collar and rock the fixing flange several times to match the position of the bolt hole.
4. Insert the fixing bolt into the hole and turn the bolt by hand to confirm that the bolt is not screwed in due to the deviation of the bolt hole.
5. As shown in Figure 1, the locking bolts are locked from 3 to 4 stages from incomplete locking to locking, and are repeatedly tightened in the order of diagonal lines. When the split inner ring or outer ring is tightened, the outer ring or inner ring of the body shape is slightly rotated to correct the deviation of the inner and outer rings from the main body.
6. When installing the fixing flange, consider the dimensional tolerances of the mounting parts so that the flange presses the inner and outer rings from the side. At the same time, it can also be excessively pressed to cause bearing deformation, affecting bearing rotation flexibility and life.
7. Design of the support base and the fixed flange Because the crossed roller bearing is a thin-walled small structure, the rigidity of the support base or the fixed flange should be fully considered. (Fig. 2) When the outer ring is of the split type, if the rigidity of the support base or the fixing flange and the fixing bolt is insufficient, the inner ring or the outer ring cannot be uniformly fixed, and the bearing will be deformed when subjected to a moment load, therefore, The contact area of the roller becomes uneven and the performance of the bearing is significantly reduced.
Third, check after installation
1. Bearing rotation check. After the bearing is installed, check the operation to check if the installation is correct. The small machine can be rotated by hand to confirm whether the rotation is smooth. The inspection items have poor operation due to foreign matter, scratches, and indentations. The installation is poor, the torque generated by the mounting is not stable, and the torque is too large due to too small clearance, installation error, and sealing friction. Wait. If there is no abnormality, the power running can be started.
2. The bearing power operation check starts from the no-load low speed and slowly increases to the rated operation of the specified conditions. The items to be checked during the test run are whether there are abnormal sounds, changes in the temperature of the crossed roller bearings, leakage or discoloration of the lubricant, and the like. If an abnormality is found, stop the operation immediately, check the machine, and remove the bearing check if necessary.
3, bearing temperature check, can be estimated based on the external temperature of the bearing housing. However, it is more accurate to directly measure the temperature of the outer ring of the bearing by using the oil hole. The rolling bearing temperature gradually increases from the start of the operation, and the temperature is usually stable after 1 to 2 hours. If the bearing is poorly installed, the temperature will rise sharply and an abnormally high temperature will occur. The reasons are such as excessive lubricant, too small clearance of the cross roller bearing, poor installation, excessive friction of the sealing device, and the like.
4. Bearing sound inspection, the rotation sound of the crossed roller bearing is checked with a stethoscope, etc., and there are strong metal noise, abnormal sounds, irregular sounds, etc. to explain abnormalities. The reasons are poor lubrication, poor accuracy of the shaft or housing, bearing damage, and foreign matter intrusion.
