GQZ Technology Knowledge: Compound Grinding of Outer ring raceway and rib of Cylindrical Roller Bearing
The structure of compound grinding and dresser and the adjustment of dressing mechanism and grinding wheel.
Abstract: Through the transformation of the grinding wheel dresser of the internal grinder, the compound grinding of the two ribs and raceway of the outer ring of the cylindrical roller bearing is realized, which effectively improves the machining efficiency and quality.
Key words: Cylindrical roller bearing; Internal grinder; Trimming mechanism; Compound grinding
3MZ208 and 3MZ2015 grinding machines are mainly used for grinding the inner bore of bearings and roller bearing raceway. Our company improved them and adopted the method of combining processes to realize the compound grinding of cylindrical roller bearing outer race and retaining edge, which effectively solved the problem of low processing efficiency of retaining edge of this kind of products, and the processing quality of products has also been reliably guaranteed.
1. Structure of compound grinding and dresser
The combined process grinding method is to use the outer circle and two end faces of the grinding wheel to participate in the grinding, and simultaneously grind the two ribs and raceways of the ferrule by the cutting method (Fig. 1). During grinding, the workpiece rotates and cuts horizontally, and the grinding is completed under the high-speed rotation of the grinding wheel. In the grinding process, the allowance of the outer ring raceway is mainly removed by the outer circle of the grinding wheel, and the allowance of the two ribs of the outer ring is mainly removed by the sharp corners of the grinding wheel, so the sharp corners of the edges of the grinding wheel are also very easy to wear.
Fig. 1 Cutting in method for grinding two ribs and raceway
The width dimension of the grinding wheel and the parallel difference between the two ends directly affect the processing quality of the retaining edge and raceway. Therefore, in order to ensure the geometry and cutting performance of the grinding wheel, the grinding wheel must be trimmed after each grinding process. The dressing mechanism of the original grinder can only trim the outer circle of the grinding wheel, and cannot obtain the accurate width size and regular sharp angle of the grinding wheel, so it is impossible to carry out combined process grinding; In addition, the process is dispersed, and the processing process must be positioned repeatedly, which will affect the processing efficiency and quality. The improved grinding wheel dressing mechanism has the functions of end face dressing and cylindrical dressing (Fig. 2 and Fig. 3). Diamond pen 1 is used for grinding wheel excircle dressing, and diamond pens 2 and 3 are fixed on the end face dresser for grinding wheel end face dressing; The end face dresser is supported by the end covers on both sides of the original dresser and fixed with screw 1, so that the centers of diamond pens 2 and 3 are located in the same horizontal plane, and the overall structure is stable and reliable; The end face trimming and outer circle trimming are realized by using the control of the dresser reverse lift oil cylinder.
Fig. 2 Grinding wheel excircle dressing
Fig.3 Grinding wheel end face dressing
The modified dresser has convenient adjustment and good rigidity of the overall structure, which can effectively ensure the dressing quality of the grinding wheel. At the same time, due to the one-time grinding of the retaining edge width, the machining accuracy of the retaining edge width and parallelism difference is greatly improved compared with the scattered process grinding.
In the actual machining process, because the retaining edge is not perpendicular to the cutting surface of the raceway, but there is a certain angle, when the grinding wheel cuts and grinds, the wear of the two end faces of the cut part can compensate the angle of the retaining edge. In addition, when selecting the grinding wheel, in order to avoid the sharp corner of the grinding wheel falling off due to insufficient strength in the process of grinding retaining edge, the hardness of the grinding wheel should be higher than that in single grinding. The width of the grinding wheel shall be 1 ~ 2mm wider than the width of the raceway to realize one-time dressing and forming. If the margin is too large, adjust the spacing of diamond pens 2 and 3 for multiple dressing to the width of the raceway.
2. The adjustment of dressing mechanism and grinding wheel
Dressing mechanism is mainly the adjustment of the overall position of the mechanism and the height of the diamond pen tip relative to the center of the grinding wheel. When adjusting the position of the mechanism, loosen the fastening nut of the dressing mechanism, adjust its front and rear positions and the suspension length of diamond pen 1 to ensure that the reverse lifting of the dresser does not interfere with the grinding wheel shaft during operation; When the relative height of the nib is adjusted, the height adjustment of the diamond pens 2 and 3 is controlled by the fine-tuning screw 2, so that the two nibs are in the same horizontal plane. The height of diamond pen 1 is controlled by screw 1. After the adjustment, lock the screw 1 to fasten the end face dresser and the cylindrical dresser together to ensure the overall rigidity.
Dressing the two end faces of the grinding wheel: adjust the position of diamond pens 2 and 3 so that the width between the pen tips is equal to the width of the raceway of the processed ferrule, and fix and lock it; When the grinding wheel rotates at high speed, the dresser cuts horizontally to the appropriate position to complete the end face dressing process (Fig. 4b). Because the left and right end faces of the grinding wheel are parallel, the effective finishing of the left and right end faces is ensured. The end face trimming is completed at one time when the grinding wheel is replaced, and it will not be trimmed in the subsequent grinding process. It should be noted that: (1) the trimming allowance of both ends should be equal as far as possible. (2) The adjustment of the tip spacing of the diamond pen should be equal to the width of the raceway.
Excircle trimming: adjust the diamond pen 1 to the horizontal position (Fig. 4C), the grinding wheel rotates at high speed and makes radial movement, repair the wear layer around the excircle and the worn two sharp corners (Fig. 4C, FIG. 4D), and complete the excircle trimming process. Dressing is mainly carried out after replacing a new grinding wheel and during the grinding cycle. Since only the outer circle of the grinding wheel is trimmed in the machining cycle, in order to obtain the sharp angle of the edge of the grinding wheel, the trimming compensation amount should be larger than that of the single inner circle grinding, which can be appropriately selected according to the edge allowance and edge height. (b) end repair (c) outer circle repair (d) after grinding (E) Fig. 4 grinding wheel dressing process after the towel block is newly repaired to the outer circle. In the actual machining process, because the retaining edge is not perpendicular to the cutting surface of the raceway, but there is a certain angle, when the grinding wheel cuts and grinds, the wear of the two end faces of the cutting part can compensate for the angle of the retaining edge. In addition, when selecting the grinding wheel, in order to avoid the sharp corner of the grinding wheel falling off due to insufficient strength in the process of grinding retaining edge, the hardness of the grinding wheel should be higher than that in single grinding. The width of the grinding wheel shall be 1 ~ 2mm wider than the width of the raceway to realize one-time dressing and forming. If the margin is too large, adjust the spacing of diamond pens 2 and 3 for multiple dressing to the width of the raceway.
(a) New grinding wheel (b) End face dressing (c) Cylindrical trimming
(d) After grinding (e) After refinishing the outer circle
The processing method of combining processes is adopted to process the outer ring retaining edge and raceway of cylindrical roller bearing. The three processes of two ribs grinding and raceway grinding are combined into one process, which avoids the problems of non-coincidence of positioning datum and dimensional accuracy error caused by turning over the two ribs, greatly improves the processing efficiency and saves the investment of equipment.
More about GQZ Cylindrical Roller Bearing：
GQZ precious-quality cylindrical roller bearing with reasonable price for customers all over the world and first-class service and unrivaled products.
Some cylindrical roller bearings have no ribs on either the inner or outer ring, so the rings can move axially relative to each other. These can be used as free-end bearings. Cylindrical roller bearings, in which either the inner or outer rings has two ribs and the other ring has one, are capable of taking some axial load in one direction Double-row cylindrical roller bearings have high radial rigidity and are used primarily for precision machine tools.
In bearings of this type, the cylindrical rollers are in linear contact with the raceways. They have a high radial load capacity and are suitable for high speeds. GQZ Cylindrical Roller Bearings include NU Series, NJ Series, NUP Series, N Series, NF Series, RNU Series bearing, and RN Series bearing.
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