In the vertical turning equipment, the rotary table is one of the central structures that embody the overall functions of the machine tool and realize the machining accuracy of the workpiece. We require it to run at high speed and bear heavier workpieces, have precise running accuracy and very high anti-overturning moment ability, 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 together. This arrangement method has a messy structure and uses more materials. Especially when installing large box parts, the space of the entire machine tool is even greater. It is also difficult to adjust the slewing bearing device and pre-tightening, the alignment is even more difficult to guarantee, and the overall accuracy of the worktable is difficult to improve.
Therefore, more designs are now beginning to choose more compact interspersed roller bearings, which not only saves material costs, but also simplifies design schemes, higher limit speeds, better running accuracy and stability, and stronger load-bearing capabilities and rigidity. This article introduces Ruan's application of interspersed roller slewing bearings on vertical lathes to achieve its perfect engineering functions.
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 workbench can be reduced to the greatest extent 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 final 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 only to pay attention to the bearing assembly runout, but to have an in-depth 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. As the outer ring rotates the parts, 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 static 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 of the device, the inner ring of the locking ring, or the bearing is loaded Oblique, that is, migraine occurs. This kind of misalignment will cause stress concentration in the gap between the contact area of the roller and the raceway, causing serious scratches, cratering and peeling, and the bearing life will be completed earlier.
3. Form and position
The device surface of the shaft and the gear ring is required to have the same flatness, perpendicularity, roundness and cylindricity as the fine bearing. Controlling these shapes and positions can not only achieve better installation accuracy, but also prevent excessive stress concentration on the inner and outer rings of the bearing and prolong the service life of the bearing. Regarding the processing specifications of the shape and position, it is recommended to consult the bearing supplier to match its bearing accuracy.
Fourth, the axial preload
In the cutting test of the vertical lathe, the end face and the outer circle roughness of the workpiece are very concerned, and one of the keys to determine the advantages and disadvantages is the rigidity of the system. The rigidity of the system includes the rigidity of the frame structure and the rigidity of the supporting bearing, among which the rigidity of the bearing often depends on its axial preload.
Therefore, it is particularly important to properly set the axial preload of the bearing with full consideration of the effects of temperature and load.
