Abstract: This paper analyzes the main influencing factors of the machining error of the curvature radius of the roller ball base surface, and combines examples to analyze the influence of the grinding wheel radius and its rotation angle on the curvature radius of the roller ball base surface. It is concluded that the adjustment error of the grinding wheel rotation angle is the main cause of the curvature radius error of the roller ball base surface. Finally, improvement suggestions are given.
Keywords: convexity roller; Spherical base; Normative grinding; Curvature radius; Sand cycle angle
The shape and quality of the base surface of the roller ball will have an impact on its contact with the large retaining edge of the inner ring, lubrication status, and bearing service life. The tapered roller bearing adopts a ball base surface roller and inclined edge structure, which can improve the lubrication state of the roller end face and the edge, facilitate the formation of lubricating oil film, reduce sliding friction, reduce friction and temperature rise, make the bearing run smoothly, and improve the bearing capacity.
1. Processing principle of roller ball base surface
The base surface of roller balls is often ground using the generative method, which is a machining method in which the workpiece and tool being processed move relative to each other according to a certain trajectory and fit each other. The principle of generative grinding of roller ball base surface is shown in Figure 1.
Figure 1 Schematic diagram of generative grinding principle for roller ball base surface
During grinding, the roller is installed inside the base sleeve, which drives the roller. The roller axis intersects with the grinding wheel axis in the same plane and rotates around their own axis. The grinding wheel feeds and grinds to produce the base surface of the roller ball. During the conventional grinding process, the grinding wheel continuously feeds and the workpiece gradually forms. The grinding wheel achieves self sharpening by friction with the workpiece, without the need for trimming.
2. Error analysis
The curvature radius SR of the base surface of the roller ball is
SR=R/sin α ， (1)
In the formula: R is the average radius of the cylindrical grinding wheel; α The angle between the axis of the cylindrical grinding wheel and the axis of the roller (i.e. the rotation angle of the grinding wheel). The curvature radius of the base surface of the roller ball is closely related to the rotation angle of the grinding wheel and the radius of the grinding wheel. There are three main factors that affect the machining error of the curvature radius of the roller ball base surface.
2.1 Position error
The wear of the base sleeve will cause lateral displacement of the roller, causing the axis of the roller and the axis of the grinding wheel to not intersect in the same plane, making it difficult to ensure the quality of the processing of the base surface of the roller ball. Therefore, it is necessary to avoid using base sleeves with worn cylinder walls.
2.2 Grinding wheel error
The grinding wheel is made by firing a mixture of abrasive and binder, and the presence of granular abrasive particles can cause certain machining errors in the size of the grinding wheel, resulting in errors in the curvature radius of the roller ball base surface.
2.3 Adjustment error
In the grinding process of roller ball base surface, when the grinding wheel is determined, the curvature radius of the roller ball base surface is determined by the rotation angle of the grinding wheel α Control. The adjustment of the grinding wheel angle of the existing conical roller ball base grinding machine 3M4372 relies on a rack, making it difficult to accurately adjust the return angle α， This will directly lead to errors in the curvature radius of the machined roller ball base surface.
3. Example analysis
Taking a certain type of roller as an example, compare and analyze R, α The influence on the curvature radius of the base surface of the roller ball. The process requires a curvature radius of (1238 ± 30) mm on the base surface of the roller ball, a turning angle of 6 ° 23 'for the grinding wheel, and a radius of 137.5 mm for the selected grinding wheel. According to equation (1), the influence of the error between the grinding wheel rotation angle and the grinding wheel radius on the curvature radius of the roller ball base surface can be obtained, as shown in Table 1.
Table 1 Comparison of Curvature Errors of Roller Ball Base Surface
When the rotation angle of the sand wheel is determined（ α = The influence of grinding wheel radius error on the curvature radius SR of the roller ball base surface is shown in Figure 2 at 6 ° 23 '.
Figure 2 SR-R Curve
By analyzing the SR-R curve, it can be seen that the change in the curvature radius of the roller ball base surface caused by the radius error of the grinding wheel is relatively small. Even if the manufacturing error of the selected grinding wheel radius is ± 2 mm, the curvature radius of the roller ball base surface is still within the allowable range of the process. However, the manufacturing error of the radius of the cylindrical grinding wheel used in actual processing is within ± 1 mm. Therefore, the machining error of the curvature radius of the roller ball base caused by the manufacturing error of the grinding wheel radius can be ignored.
When the radius of the grinding wheel is determined (R=137.5 mm).
Analyze SR - α The curve shows that a small change in the rotation angle of the sand wheel can cause a significant change in the curvature radius of the base surface of the roller ball. Due to the low accuracy of the grinding wheel angle adjustment of existing equipment, the adjustment error of the grinding wheel rotation angle is relatively large. Therefore, the adjustment error of the grinding wheel rotation angle in actual processing is the main reason for the machining error of the curvature radius of the roller ball base surface.
4. Conclusion
In summary, the error in the curvature radius of the roller ball base surface in actual processing is mainly caused by the adjustment error of the sand wheel rotation angle. Therefore, by improving the sand wheel rotation angle adjuster, such as installing a grating angle display device, the adjustment error of the sand wheel rotation angle can be minimized as much as possible to ensure the machining accuracy of the curvature radius of the roller ball base surface.
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