The reason why the bearing forms a spiral defect in the grinding process

During the grinding process, the bearing surface is ground through a high-speed rotating grinding wheel. Therefore, if you do not operate and adjust the equipment according to the work instructions during grinding, various defects appear on the bearing working surface, which may affect the bearing. The overall quality of the bearing. Bearings in the precision grinding, due to the high roughness requirements, the surface of the grinding marks can often be observed with the naked eye to the surface grinding traces are mainly the following. The occurrence of traces of cross-helix marks on the performance is mainly due to the poor straightness of the generatrix of the grinding wheel and the presence of bumps. During grinding, the grinding wheel and the workpiece are only partially in contact. After the workpiece or grinding wheel has been moved back and forth several times, Workpiece performance will reproduce the cross spiral and can be observed with the naked eye. The pitch of these spirals is related to the speed of the workpiece table and the speed of the workpiece. It is also related to the non-parallel of the axis line of the grinding wheel and the guide rail of the table.

(a) The main causes of spiral formation:

1. The dressing of the wheel is poor, corners are not chamfered, and no coolant is used for dressing;

2. The guide rail guides too much lubricating oil, causing the worktable to float;

3 machine tool accuracy is not good;

4. Grinding pressure is too large.

(b) Specific causes of spiral formation:

1. The V-shaped guide rail is not good in rigidity, and the grinding wheel is offset when grinding, but the edge of the grinding wheel is in contact with the working surface; the valve inlet pump

2. The speed of reversing the worktable is not stable and the precision is not high when repairing the noisy wheel, and the dressing of the edge of the grinding wheel is slightly less;

3. The workpiece itself is poor in rigidity;

4. The grinding wheel has broken and exfoliated sand particles and the iron scraps under the grinding of the workpiece accumulate on the surface of the grinding wheel. For this reason, the finished grinding wheel should be washed or brushed with cooling water;

5. The dressing of the grinding wheel is not good, there are local bulges and so on. The main reason for the appearance of scale-like marks on the surface of fish scales is that the cutting edge of the grinding wheel is not sharp enough and “gripping” occurs during grinding. At this time, the vibration is large.