Working principle and improvement effect of inner ring groove machining of thin wall bearing by escape grinding method

Abstract: This paper analyzes the reasons why the common grinding methods of thin-walled ferrule are easy to cause ferrule deformation and low machining efficiency, and introduces the working principle and improvement effect of machining inner ring channel by escape grinding method.

Key words: thin wall bearing; thin section bearing, Escape grinding method; Deformation; Processing efficiency

There are many methods for bearing ring grinding, but there has been no effective solution for thin-walled ring. This is because the stiffness of the thin-walled ring is too low. No matter clamping or processing, slight loading is easy to lead to deformation, which is difficult to ensure the dimensional and geometric accuracy required by the process. Therefore, the grinding of the thin-walled ring is always a difficulty in the bearing manufacturing.

1. Common Grinding Methods

For the thin-walled inner ring groove, the common grinding methods include "branch diameter grinding groove" (support inner diameter grinding inner groove), "branch groove grinding groove" (support inner groove grinding inner groove), and "Branch edge grinding groove" (support retaining edge grinding inner groove), etc. Taking "branch diameter grinding groove" as an example, its grinding principle is shown in Figure 1. The machining error of inner diameter in grinding will be reflected on the inner groove; The front and rear supports make the center of the workpiece and the center of the grinding wheel basically on the same horizontal plane, and the workpiece directly bears the cutting force fed by the grinding wheel. When the feed rate is too large and exceeds the deformation resistance of the workpiece, the workpiece will be deformed, which makes it difficult to control the accuracy of workpiece size and roundness. In the actual processing, the operating tools are required to have a high skill level and rich practical experience. Generally, 1μm. If the one-time feed is too large, it may cause waste products, and the processing efficiency is very low. Taking the inner ring with an inner diameter of about 100 mm as an example, the shift production is only about 10 pieces.

Fig. 1 Schematic diagram of branch diameter grinding ditch

2. Escape Grinding Method

After many tests, a "escape grinding method" especially suitable for the processing of thin-walled inner ring groove has been explored, that is, when the feed rate of grinding wheel is large, the workpiece can automatically "escape" when it is extruded and deformed, which can not only ensure the machining accuracy, but also significantly improve the machining efficiency.

The key of escape grinding method is to set the workpiece support as a combined angular support of one inner support and one outer support, as shown in Figure 2. The front support is an inner support, with eccentricity in the first quadrant and bearing angle α =  15 ° ~ 20 °, eccentricity e = 0.15 ~ 0.30 mm (when this range is taken, the accuracy of wall thickness difference of workpiece is high). (2) the rear support is an external support, with the eccentricity in the fourth quadrant and the included angle between the two supports β =  30° ～ 45°.

Fig. 2 Schematic diagram of escape grinding method

Working principle of escape grinding method: when the grinding wheel is fed to grind the workpiece, if the cutting force exceeds the clamping force of the electromagnetic centerless fixture, the workpiece will be separated from the outer support of the fourth quadrant to avoid deformation caused by grinding wheel extrusion and still maintain the original shape. With the grinding to a certain size, the workpiece falls back to the outer support for normal grinding. Repeat until grinding to the required size.

3. Improvement Effect

Using escape grinding method, because the workpiece can automatically "escape" in grinding to avoid the influence of deformation, it can achieve high machining accuracy and greatly reduce the scrap rate. In addition, without considering the problem of excessive feed of grinding wheel, not only the general operators can complete it, but also the shift production of the same workpiece is increased from the past 10 to about 50, and the processing efficiency is increased by about 5 times. At present, this grinding method has been verified and popularized in many products of two materials (stainless bearing steel 9Cr18 and high carbon chromium bearing steel GCr15) (including the "branch groove grinding diameter" of Thin-walled bearing outer ring). The effect is very obvious, and the problem that it is difficult to process Thin-walled bearing ring has been well solved.

More about GQZ Thin Wall Deep Groove Ball Bearing:

The difference between thin-walled ball bearings and traditional deep groove ball bearings is that the cross-section of each series is designed as a fixed size and will not increase with the increase of inner diameter. In order to support different types of loads, thin-walled ball bearings have three types: radial contact (L-type), angular contact (M-type) and four point contact (N-type).

Thin wall bearings are suitable for rotating mechanisms that require compact, simple and lightweight design in modern machinery. It has the characteristics of small volume, light weight and small friction. Small volume, light weight, saving space, reducing weight, reducing overall size, low friction and good rotation accuracy.

The diversity of thin-walled ball bearings makes them suitable for a wide range of applications, such as aerospace, semiconductor processing equipment, robots, medical equipment and so on.

Founded in 1999, Wuxi Guangqiang Bearing Trade Co.,LTD, deals with precision bearings and bearing related products across a large spectrum of customers. Since the founding the company, we keep standing by the principle of "Quality First, Credit First, Independent Innovation" and our company has won a great reputation from home and abroad.