Double row cylindrical roller bearing with tapered bore belongs to linear contact bearing, its bearing capacity and rigidity are higher than that of point contact angular contact bearing, and it is often used in medium and large bearing with large load, high rigidity and relatively low speed. , Heavy-duty machine tool spindle system. The following will share with you the assembly and adjustment method of double row cylindrical roller bearings used in the spindle system.

1. Selection of main shaft rolling bearings.

Both the spindle and the bearing have manufacturing errors, which will inevitably affect the rotation accuracy of the spindle assembly. When the spindle assembly is assembled, if the error effects of the two are partially offset with each other, the rotation accuracy can be further improved. Since the inner ring of the rolling bearing rotates with the main shaft, its radial runout (or runout) has the greatest impact on the bearing rotation accuracy. Therefore, generally only the relative position of the bearing inner ring and the main shaft journal is adjusted.

(1) Front bearing selection: Since the radial runout of the main shaft at the front support has the greatest impact on the rotation accuracy of its end, the bearing selection method should be used first to reduce the radial runout at the front support. The actual operation process is to measure the inner ring and main shaft journal of a batch of rolling bearings separately before assembly, and type the mark at their respective high points (for bearings in some countries, the high point has been marked, and in recent years, with the With the improvement of bearing accuracy, the mark will be removed); then grouped according to the actual radial runout, whichever is similar to the runout is assembled, so that the high points of the two are opposite to each other, that is, the selection of the front bearing is completed.

(2) Rear bearing selection: After the front bearing is selected, the rear bearing can be selected to further improve the rotation accuracy of the main shaft assembly. Since the main shaft uses the same datum to grind each journal, the high points of the front and rear journals to the main shaft heartbeat are often in the same direction. Therefore, as long as the high points of the rear bearing and the front bearing are arranged in the same axial plane and the axis is on the same side, better results are often obtained. If the radial jump height points of the outer ring of the front and rear bearings are installed in the same direction and different from the high point of the seat hole, the rotation accuracy of the main shaft can be further improved.

2. The clearance (clearance) of the main shaft rolling bearing and its adjustment.

The amount of clearance (clearance) of the main shaft rolling bearing has an important influence on the working performance of the main shaft assembly and the life of the bearing. When the bearing works under a large clearance, it will cause the offset of the spindle position (radial or axial) and directly affect the machining accuracy. At this time, the bearing area of the bearing is also small, and the load concentrates on one or several rolling elements in the direction of the force, resulting in a large stress concentration, causing the bearing to become mature and wear aggravated and reduce its life.

In addition, the stiffness and vibration resistance of the spindle assembly is greatly reduced. When the bearing is adjusted to zero clearance, the bearing area increases accordingly, the force condition of the rolling elements tends to be uniform, and the rotation accuracy of the main shaft is improved. When the bearing preload (preload) is adjusted to a negative clearance, the rolling elements will be elastically deformed, the contact area with the raceway will be increased, and the bearing area will be expanded to 360°, so the stiffness and vibration resistance of the spindle assembly can be improved. significantly improved. Therefore, maintaining a reasonable amount of clearance in the rolling bearing is an important measure to improve the rotation accuracy, stiffness and vibration resistance of the spindle assembly.

The static stiffness of the spindle assembly increases as the amount of bearing clearance decreases. The stiffness change (curve slope) of the bearing is the largest near zero clearance, and then the stiffness increases more slowly. However, the effect of bearing clearance on the dynamic characteristics of the spindle assembly is more complex. The damping value of the main shaft assembly (the ratio of the actual damping value to the critical damping value is the damping ratio first increases with the decrease of the bearing clearance, the damping value at the zero clearance is the largest, and then the interference increases with the decrease of the clearance amount. larger), the damping value also decreases.

3. Inspection and adjustment of the correct installation of the inner and outer rings of the bearing.

The ratio of diameter to width of double row cylindrical roller bearings is generally between 4 and 7. Due to the large diameter and width of double row cylindrical roller bearings, the guiding performance is poor when installed in the headstock hole and on the main shaft. In addition, the large size and quality of large machine tool parts bring certain difficulties to the assembly work, and it is easy to cause uneven force when installing the bearing. For the above reasons, the installation position of the inner and outer rings of the main shaft bearing is shifted, and the contact between the bearing rolling elements and the inner and outer rings of the bearing is poor, resulting in the reduction of the rigidity and rotation accuracy of the main shaft. The method of checking the correct installation of the inner and outer rings of the main shaft bearing is as follows: During the process of preloading the inner ring of the bearing, the main shaft is continuously rotated, and the rotation of the bearing rolling elements is observed at the same time.

If the main shaft rotates easily and the rolling elements of the bearing rotate with the rotation of the main shaft, the inner and outer rings of the bearing should be installed correctly; if the main shaft already has a certain amount of preload, it will feel blocked when rotating, and the individual rolling elements of the bearing do not follow the rotation. If the main shaft rotates and rotates, or the respective rolling elements are loose when moved by hand, it should be caused by the misalignment of the inner ring or outer ring of the bearing.

The magnetic gauge seat can be installed on the main shaft box and the main shaft respectively, rotate the main shaft and observe the change of the indication value of the dial indicator, adjust the position of the inner ring and outer ring of the bearing, so that the change of the indication value of the dial indicator is the smallest (generally should be less than 0.01 ~0.04mm, related to the bearing size). At this time, the inner ring and outer ring of the bearing have been installed correctly. Figure 1 Check whether the bearing outer ring is installed correctly. Figure 2 Check whether the bearing inner ring is installed correctly. If the bearing, 3 spindle box, 4 dial indicator, and 5 magnetic force meter seat move, it means that the spindle box body or the spindle diameter is not round.