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Application of KOYO Cross Roller Bearings on the Spindle of

Writer: Eric Bearing Limited

With the development of science in recent years, high-precision, high-speed machine tools are favored by the market. It also makes the machining accuracy of the vertical lathe continue to a new height. Crossed roller bearings play a key role in improving the machining accuracy of vertical turning. Today, Eric Bearing Limited first compares the KOYO crossed roller bearing spindle structure with the ordinary bearing spindle structure, and then focuses on the application of KOYO crossed roller bearing on the vertical lathe spindle.

In the vertical lathe spindle structure, the spindle bearing, as the core component of the table rotation, plays a vital role in ensuring its rotation accuracy. The traditional vertical lathe spindle structure has two bearings to support the spindle. Thrust ball bearings bear axial loads, cylindrical roller bearings mainly bear radial loads. The disadvantages of this structure are that there are many structural parts, large axial dimensions, and cumbersome adjustment links, resulting in lower overall structural rigidity. KOYO 6203ZZC3  bearings online , pls click here : 

KOYO crossed roller bearings consist of two rows of bearing raceways and rollers that are perpendicular to each other. The rollers are arranged alternately above the raceways, so the bearing can bear axial load, radial load, overturning moment and other Compound load; although the cross section of the bearing is relatively small, its rigidity is very high, which can replace the arrangement of traditional spindle bearings. Tapered rollers can effectively reduce the linear velocity difference between the inner and outer rings of the raceway when the bearing rotates at high speeds, and prevent rollers and rolling The relative sliding of the contact surface of the raceway reduces the friction and heat generation between the roller and the raceway and ensures a long life of the bearing. At the same time, the structure has fewer parts and a more compact design space, which reduces the height of the center of gravity of the worktable and the weight of the spindle structure. There are few adjustment links, and the rigidity of the overall structure of the main shaft is greatly improved, which makes the table running more smoothly.

The following describes the application of KOYO crossed roller bearings in vertical lathe spindles in detail.

1. Model selection  

According to the selection principle of the outer diameter of the bearing ≥ 1/2 the outer diameter of the worktable, select the appropriate size bearing.

2. Structure determination

The main shaft structure of the vertical lathe is composed of a ring gear, a pressure plate, a cross roller bearing and a bearing seat. The bearing seat is matched with the inner ring of the bearing, the gear ring is matched with the outer ring of the bearing, and the inner and outer rings of the bearing are fixed by pressing plates and bolts.

It should be noted that the fit between the bearing seat and the KOYO crossed roller bearing should be an interference fit, which can prevent large eccentricity during installation or load. Because the ring gear bears cyclic load, its fit with the cross roller bearing should also be an interference fit.

When processing the inner hole of the gear ring and the bearing seat shaft, the processing range of the bearing seat shaft diameter and the gear ring diameter should be calculated according to the actual inner and outer diameter dimensions on the bearing inspection sheet and the recommended matching amount. At the same time, determine the shape and position tolerance of each part according to the recommended value. The surface roughness of the KOYO bearing mounting surface needs to match the bearing. The inner hole of the gear ring and the bearing seat shaft need to be ground to achieve the specified roughness value.

3. Preparation before installation

Before installation, make sure that there are no burrs and impurities on the shaft and hole edges of the structural parts. The mating surface must be cleaned up. If necessary, the mating surface in contact with the bearing can be wiped with oil or grease. KOYO bearings are separated when delivered and are divided into bearing outer ring, lower inner ring, upper inner ring, roller and spacer. According to the installation and load requirements, the lower inner ring of the bearing and the bearing seat have an interference fit, and the outer ring of the bearing and the ring gear are also an interference fit.

In order to facilitate the installation, the lower inner ring of the bearing can be heated according to the principle of thermal expansion and contraction, and then installed on the bearing seat after the size is enlarged; similarly, heating the ring gear to expand it makes it easier to install the outer ring of the bearing. Small bearings can be heated in a metal container filled with oil. It should be noted that during heating, partitions or brackets should be used to isolate the bearing from the bottom of the container to ensure uniform heating and reduce deformation.

4. Spindle assembly

The outer ring of the KOYO bearing is hot-fitted to the ring gear and fixed by the pressure plate 6. Lift the gear ring together with the fixed outer ring of the bearing smoothly near the lower inner ring of the bearing (at this time the lower inner ring of the bearing has been hot-fitted to the bearing seat), adjust the correct installation position, and then cross the tapered rollers. Install the ground into the raceway, and then install the plastic spacers so that each roller is separated by the spacers, and finally install the inner ring of the bearing. After adjusting the adjustment pad 4, fix the upper inner ring of the bearing to the bearing seat through the pressure plate 2.

When installing the bearing, the bearing can be preloaded according to specific needs to ensure the bearing's clearance-free operation and high rotation accuracy. After adjustment, install the worktable on the ring gear, and the assembly is now complete.

5. Lubrication of the spindle

In order to ensure the safe and reliable operation of KOYO bearings, in order to avoid direct metal contact between the rolling elements and the cage in the bearing and reduce wear when the bearing is working, the bearing must be lubricated. The lubrication of the bearing is realized through the groove between the two inner rings. The inner ring of the bearing is fixed and the outer ring rotates.

The circulating lubricating oil of the cross roller bearing can be shared with the drive system. In fact, if it is only used for the lubrication of the bearing, the amount of lubricating oil only needs a small amount, but the temperature of the KOYO bearing will rise rapidly when the spindle rotates at a high speed. At this time, a large amount of lubricating oil will be needed. The flow of lubricating oil can improve the heat dissipation conditions of the KOYO bearing, and has a cooling effect on the KOYO bearing, which can ensure the normal use of the bearing under high temperature conditions.

6. Application Summary

The application of KOYO crossed roller bearings in vertical lathes has been very successful, greatly improving the accuracy of the machine tool, and its geometric accuracy is particularly improved when rotating at high speeds, but it is undeniable that there are still many shortcomings that restrict the bearing Use, if the individual size of the bearing varies greatly, the relevant parts need to be determined according to the actual size of the bearing, and the outer ring and the lower inner ring of the bearing need to be installed with interference, and the dimensional tolerances and shape tolerances of the relevant parts are extremely high. It is difficult to form mass production.

Of course, with the improvement of machining technology and the rapid development of assembly methods, the application of cross-roller bearings on vertical lathes has become more and more extensive.