According to the working accuracy, rigidity, temperature rise and structural complexity of the main shaft components, there are many different configurations of rolling bearing support. When using double-row tapered roller:
The front support adopts the combination of double-row short cylindrical roller bearing and 60 ° angular contact ball bearing to bear radial load and axial load, and the rear support adopts diagonal contact ball bearing. This configuration can improve the comprehensive rigidity of the main shaft, meet the requirements of strong cutting, and is widely used in various digital control machine tools.
The front support adopts double-row tapered roller bearing to bear radial load and axial load, and the rear support adopts single-row tapered roller bearing. This configuration can bear heavy load and strong dynamic load, and has good installation and adjustment performance, but the improvement of spindle speed and accuracy is limited, which is suitable for CNC machine tool spindles with medium accuracy, low speed and heavy load.
Before installation of double-row, four-row or paired tapered roller bearings, the preset clearance is designed. For example, when the inner spacer, outer spacer and inner and outer spacer are set, the preset clearance is based on the use and installation of the bearing. For bearings with preset clearance, the original axial clearance of the bearing has been fixed. Users can directly install and use the bearing without adjusting the spacer, thus simplifying the installation procedure.
For double-row and four-row tapered roller bearings and matching bearings, the preset clearance is required according to the axial clearance. The radial clearance in the above table can be converted into the axial clearance according to the following formula.
Ga=Gr*cot α
Ga: axial clearance
Gr: radial clearance
α： Contact angle of tapered roller bearing
Double-row tapered roller bearing
The geometry of the double-row tapered roller bearing allows the rollers to slide between the raceways, which means that the rollers cannot slide freely when the rollers are loaded. Tapered roller bearings have minimum load requirements to ensure that there is no slipping between rollers and raceways. Because slipping is harmful, it will destroy the lubrication of roller or raceway surface, which will lead to contact surface wear and premature bearing failure.
In addition, due to the unique design of tapered roller bearings, the friction is reduced, thus reducing the heat during operation. The tapered shape makes the roller transmit load evenly when rolling. This greatly reduces wear and improves durability. Now it has been widely used in transmission shaft and rotating shaft.