There Are Many Reasons For Bearing Running Circles

The running circle of the bearing means that the rolling bearing and the shaft or hole that it cooperates with have slipped relative to each other.

Fault phenomenon:

The temperature of the bearing part is high, and the vibration is large. Open it and see that there are slip marks on the surface of the inner ring of the shaft and bearing seat, and even grooves are worn out on the surface of the shaft or hole. From this condition it has been concluded that the bearings run out of laps.

The negative impact caused by the running of the bearing on the equipment is very large, aggravating the wear of the matching parts, and even reporting fees, damaging the equipment and reducing the accuracy of the machine. In addition, increasing the friction force, converting a large amount of energy into useless heat and noise, reducing efficiency. Therefore, in this case, maintenance should be arranged as soon as possible according to the actual situation.

Reasons for running laps:

The cooperation between the bearing and the shaft (hole) requires very strict requirements on the machining accuracy, fit tolerance, installation and assembly accuracy, material, and use and maintenance of the shaft, hole, and bearing. If any aspect is not good, the bearing may run around.

1. Fitting tolerance:There are strict standards for fitting tolerances between bearings and shafts (holes). Different specifications, precision, stress conditions, and use environments have different requirements for fitting tolerances. The friction between the rolling element and the bearing inner and outer casing is rolling friction, and the friction coefficient of the two contact surfaces is very small, and the friction force is also very small (when there is lubricating oil between the rolling element and the inner and outer casing, the friction coefficient will be smaller). The bearing and the shaft (hole) are very tightly matched, generally an interference fit, and a few cases are a transition fit. The mutual extrusion force is relatively large, resulting in static friction, and the static friction force is greater than the torque that makes them slide relative to each other, so the bearing, shaft and hole can remain relatively static, and the mechanical energy is transmitted by the rotation of the rolling body and the inner sleeve (or between the outer sleeve). If the matching tolerance between the bearing and the shaft and the hole is too large, it is a clearance fit, and the extrusion force becomes smaller. Ring phenomenon”, the inner ring of the bearing and the shaft slip is called the inner ring, and the outer ring of the bearing and the bearing seat hole slips is called the outer ring.

2. Processing accuracy and installation accuracy: Refer to the technical parameters such as the processing tolerance of shafts, bearings, and bearing housing holes, surface roughness, and installation and assembly accuracy. These countries also have industry standards. Once the standard is not met, it will affect the fit tolerance and cause the bearing to run around. The fit position of the shaft and bearing requires a very smooth surface, with a roughness Ra≤1.6μm. If it is greater than this, the burrs will be pulled off during the disassembly and assembly of the bearing, resulting in thinner shafts, larger holes, and larger fit clearances, which is reasonable The tolerance fit is violated. For example, if the coaxiality of the installation is not enough, the bearing will vibrate greatly, cause the shaft to bend, increase the load, cause the bearing to fail, increase the number of replacement bearings, affect the dimensional tolerance of the bearing and the shaft or hole, and destroy its connection with the shaft or hole. Shaft (bore) fit tolerances, all of which have the potential to cause the bearing to run and fail.

3. The material of the shaft and bearing is also very critical. Different types of bearings should be made of suitable bearing steel, with high strength and rigidity, good wear resistance, and a small friction coefficient of the bearing alloy, so as to ensure the normal use of the bearing and reduce the possibility of running circles.

4. Daily maintenance:

(1) The coupling and its wearing parts are severely worn, and the concentricity and concentricity will damage the installation degree.

(2) The locking parts of the bearing, such as the lock nut, collar, end cover, etc., are not locked in place, which will damage the matching accuracy of the bearing.

(3) Poor lubrication, increased ball wear, increased temperature, uneven thermal expansion of bearings and fittings, and damage to fit accuracy.

(4) The disassembly and assembly of the bearing is not standardized, damaging the shaft or bearing, and destroying the matching accuracy.

(5) The anchor bolts of the bearing seat are not fastened well, which causes vibration and is also the cause of damage to the bearing.