There are two types of crossed roller bearings, one is crossed cylindrical roller bearings, the other is crossed tapered roller bearings; crossed roller bearings have a long history of application outside, but only in recent years. Into the public's vision, it is widely used due to its own uniqueness and incomparable advantages over other bearings. Many users will have some problems with the installation of crossed roller bearings, such as lubrication, installation, cleaning, etc. Today, I will explain to you, I hope it will be helpful to you.
1. Choose grease
Lubrication has an important influence on the operation and life of crossed roller bearings. Here is a brief introduction to the general principles of selecting grease. Grease is made of base oil, thickener and additives. Different types of greases with the same type and different grades have very different performances and different allowable rotation limits. Be careful when selecting them. The performance of lubricating grease is mainly determined by the base oil. Generally, the low viscosity base oil is suitable for low temperature and high speed, and the high viscosity base oil is suitable for high temperature and high load.
The thickener is also related to the lubricating performance, and the water resistance of the thickener determines the water resistance of the grease. In principle, different greases cannot be mixed, and even greases with the same thickener will have adverse effects on each other due to different additives.
2. Cleaning before bearing installation
The bearing surface is coated with anti-rust oil, you must carefully clean it with clean gasoline or kerosene, and then apply clean high-quality or high-speed high-temperature lubricating grease before installation and use. The impact of cleanliness on rolling bearing life and vibration noise is very large. But we don't want to remind you that closed bearings do not need to be cleaned and refueled.
1. Thoroughly clean the main shaft, bearing seat or other installation parts, remove oil or impurities, and confirm whether there are burrs or burrs.
2. Install the crossed roller bearing into the shaft or bearing seat: Because it is a thin-walled bearing, it is easy to tilt when it is installed. In order to prevent this phenomenon, please use a plastic hammer to strike evenly while keeping it level, and carefully install the crossed roller bearing into the bearing housing or on the shaft until it is confirmed by sound that the reference surface is not completely close. Do not directly hammer the crossed roller bearing surface and the non-stressed surface. Use pressure blocks, sleeves or other installation tools (tools) to make the bearing evenly stressed, and do not install it through the transmission force of rolling elements.
If the mounting surface is lubricated, the installation will be smoother. If the interference is large, the bearing should be heated to 80~90℃ in mineral oil and installed as soon as possible, and the oil temperature should be strictly controlled not to exceed 100℃ to prevent the reduction of hardness due to tempering and the influence of dimensional recovery. When it is difficult to disassemble, it is recommended that you use the disassembly tool to pull out and pour hot oil on the inner ring carefully. The heat will expand the inner ring of the rolling bearing, making it easier to fall off.
3. Place the fixing flange on the crossed roller bearing collar and shake the fixing flange several times to match the position of the bolt holes.
4. Insert the fixing bolt into the hole, and when turning the bolt by hand, make sure that the bolt is not difficult to screw in due to the deviation of the bolt hole.
5. The locking of the fixing bolts is divided into 3~4 stages from incomplete locking to locking, and they are repeatedly tightened in the order of the diagonal. When tightening the divided inner ring or outer ring, the deviation of the inner and outer rings from the main body can be corrected by slightly turning the outer or inner ring of the body shape.
6. When installing the fixed flange, consider the dimensional tolerance of the installation parts, so that the flange presses the inner and outer rings from the side. At the same time, the bearing should not be deformed due to excessive compression, which will affect the rotation flexibility and life of the bearing.
7. The design of the support seat and the fixed flange Because the crossed roller bearing is a thin-walled and small structure, the rigidity of the support seat or the fixed flange should be fully considered. When the outer ring is a split type, if the rigidity of the support seat or the fixing flange and the fixing bolts is insufficient, the inner ring or the outer ring cannot be fixed equally, and the bearing will deform when subjected to a moment load. Therefore, the contact area of the rollers will become uneven, and the performance of the bearing will be significantly reduced.
1. Bearing rotation inspection, after the bearing installation is completed, in order to check whether the installation is correct, a running inspection should be carried out. Small machines can be rotated by hand to confirm that they rotate smoothly. The inspection items include sluggish operation caused by foreign objects, scars and indentations, unstable torque caused by poor installation and poor processing of the mounting seat, excessive torque caused by too small clearance, installation error, and sealing friction, etc. Wait. If there is no abnormality, the power operation can be started.
2. Check the power operation of the bearing, start from no-load low speed, and gradually increase to the rated operation of the specified conditions. The items to be checked during the test run are whether there is abnormal sound, temperature change of the crossed roller bearing, leakage or discoloration of the lubricant, etc. If an abnormality is found, the operation should be stopped immediately, the machinery should be checked, and if necessary, the bearing should be removed for inspection.
3. The bearing temperature inspection can generally be inferred from the external temperature of the bearing seat. However, it is more accurate to directly measure the temperature of the bearing outer ring using the oil hole. The temperature of the rolling bearing gradually increases from the start of operation, and usually stabilizes after 1 to 2 hours. If the bearing is not properly installed, the temperature will rise sharply, resulting in abnormally high temperature. The reasons are too much lubricant, too small clearance of crossed roller bearing, poor installation, too much friction of sealing device, etc.
4. Check the bearing sound, check the rotation sound of the crossed roller bearing with a stethoscope, etc. There are strong metal noises, abnormal sounds, irregular sounds, etc., indicating abnormality. The reasons are poor lubrication, poor shaft or bearing seat accuracy, bearing damage, foreign matter intrusion, etc.
1. Are there requirements for the installation surface and installation site?
Yes. If there are foreign objects such as iron filings, burrs, dust, etc. in the crossed roller bearing, it will cause noise and vibration during the operation of the bearing, and even damage the raceway and rolling elements. Therefore, before installing the bearing, you must ensure that the installation surface and installation environment are clean.
2. When lubricating bearings, is it better to apply more grease?
It is a common misconception that when lubricating crossed roller bearings, the more grease the better. Excessive grease in the bearing and bearing chamber will cause excessive agitation of the grease, resulting in high temperatures. The amount of lubricant filled in the rolling bearing is suitable to fill 1/2 to 1/3 of the inner space of the bearing, and it should be reduced to 1/3 at high speed.
3. Is the radial clearance of the bearing as small as possible?
Not all crossed roller bearings require a small working clearance, you must choose the appropriate clearance according to the conditions. In the standard 4604-93, the radial clearance of the rolling bearing is divided into five groups - group 2, group 0, group 3, group 4, group 5, the clearance values are from small to large, and group 0 is the standard clearance. The basic radial clearance group is suitable for general operating conditions, normal temperature and commonly used interference fit; rolling bearings that work under special conditions such as high temperature, high speed, low noise and low friction should choose a large radial clearance; Small radial clearance should be selected for precision spindles, machine tool spindle bearings, etc.; a small amount of working clearance can be maintained for roller bearings. In addition, for separable bearings, there is no need for clearance; the working clearance of the rear bearing after installation is smaller than the original clearance before installation, because the bearing needs to rotate under a certain load, and the fit and load of the crossed roller bearing are different. The amount of elastic deformation produced.
4. When installing or removing the crossed roller bearing, do not apply force to the connecting rivets, bolts and rollers.
5. The concentricity of the inner ring or outer ring divided by the crossed roller bearing may be slightly deviated. Therefore, before installing the bearing housing, the bolts used to fix the inner ring or outer ring can be loosened, and the deviation can be corrected with a plastic hammer, etc., and then assembled.
6. In order to improve the actual matching accuracy of the crossed roller bearing during installation, it is necessary to use the measuring method and measuring tool that does not deform the bearing to carry out the actual precise measurement of the matching surface size of the inner hole and the outer circle of the bearing. The measurement items of the outer diameter and the outer diameter are measured, and the measured data is analyzed.
7. Based on this, the size of the bearing installation part of the shaft without the seat hole is precisely matched. When actually measuring the corresponding size and geometry of the shaft and seat hole, it should be carried out under the same temperature conditions as when the bearing is not measured. In order to ensure a higher actual fit, the surface roughness of the shaft and the housing bore that does not match the bearing should be as small as possible.
Bearing life is closely related to manufacture, assembly and use, and each link must be made to make the crossed roller bearing operate better and more smoothly, thereby prolonging the service life of the crossed roller bearing.
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