In vertical lathe equipment, the rotary table is one of the core structures that reflects the overall performance of the machine tool and realizes the machining accuracy of the workpiece. We require it to run at high speed and bear heavier workpieces, while having the ability to run accuracy, and the slewing bearing supporting the table is the key to accomplish this important mission. In the past, most of the domestic workbenches used thrust bearings and radial bearings. This arrangement has a complicated structure and uses more materials. Especially when large box parts are placed, the space of the entire machine tool is larger. It is also difficult to install and adjust the pre-tightening of the slewing bearing, the alignment is even more difficult to guarantee, and it is difficult to improve the overall accuracy of the workbench. Therefore, more designs are now beginning to choose cross-roller bearings with a more compact structure, which not only saves material costs, but also simplifies the design, improves operating accuracy and stability, and has stronger bearing capacity and rigidity. So, how to apply cross roller bearings on vertical lathes? Let's follow the CNC GTC/VTC SERIES OF LARGE SCALE VERTICAL LATHE editor to have a simple understanding!
1. Runout accuracy
Bearing runout can be divided into synchronous runout and asynchronous runout. The impact of synchronous runout on the overall runout of the worktable can be greatly reduced by grinding the work surface, but the impact of asynchronous runout cannot be eliminated in this link. It is mainly determined by the outer diameter tolerance and roundness of the roller. Therefore, the better the asynchronous runout control of the bearing, the smaller the radial and axial runout of the worktable, that is, the higher the running accuracy. When selecting bearing brands and accuracy grades, it is recommended not to only focus on the bearing assembly runout, but to have a deep understanding of the accuracy standards that affect the asynchronous runout of the bearing.
2. Bearing fit
When selecting bearings, it is recommended that the inner ring and the shaft, and the outer ring and the gear ring are tightly fitted. Since the outer ring is a rotating part, the tight fitting amount should be slightly larger. The inner ring will be pressed down by the end cap and adjusted to a certain pre-tightening amount, so the tight fitting amount should be slightly smaller. However, if the inner ring is considered to be a stationary part, and the inner ring and the shaft are designed to be loosely fitted, there is a radial gap between the inner ring and the shaft, it is possible that the inner ring may be deflected when the inner ring is installed, the inner ring is locked, or the bearing is loaded. Oblique, that is, eccentricity occurs. This eccentricity will cause stress concentration at the boundary of the contact area between the roller and the raceway, causing serious scratches, cratering and peeling, and ending the life of the bearing earlier.
Three, shape and position tolerance
The mounting surface of the shaft and the gear ring is required to have the same flatness, perpendicularity, roundness and cylindricity as the bearing. Controlling these form and position tolerances can not only achieve better assembly accuracy, but also avoid excessive eccentricity of the inner and outer rings of the bearing to cause stress concentration, and prolong the service life of the bearing. Regarding the processing standards of the form and position tolerances, it is recommended to consult the bearing supplier to match its bearing accuracy.
The above is the CNC GTC/VTC SERIES OF LARGE SCALE VERTICAL LATHE editor introducing the relevant knowledge of how to apply cross roller bearings to vertical lathes. I hope you can learn more.