During the grinding process of the bearing, the working surface of the bearing is ground by a high-speed rotating grinding wheel. Therefore, if the operation and adjustment of the equipment are not carried out according to the operation instructions during grinding, various roughness will appear on the working surface of the bearing. Degree defects, so as to affect the overall quality of the bearing.

Cross helix marks appear on the surface

The reason for this kind of marks is mainly due to the poor straightness of the busbar of the grinding wheel, There is a concave-convex phenomenon. During grinding, the grinding wheel and the workpiece are only partially in contact. When the workpiece or the grinding wheel moves back and forth several times, the cross helix will reproduce on the surface of the workpiece and can be observed with the naked eye. The pitch of these helical lines is related to the speed of the workpiece table and the rotational speed of the workpiece, as well as the non-parallel relationship between the axis of the grinding wheel and the guide rail of the table.

The main reasons for the formation of the spiral line

1. The grinding wheel is not well dressed, the corners are not chamfered, and the coolant is not used for dressing;

2. Too much lubricating oil for the guide rails of the worktable, causing the worktable to float;

3. The precision of the machine tool is not good;

4. The grinding pressure is too large, etc.

The specific reasons for the formation of the spiral line

1. The rigidity of the V-shaped guideway is not good. When grinding, the grinding wheel is offset. Surface contact;

2. The reversing speed of the table is unstable and the precision is not high when dressing the noisy wheel, so that a certain edge of the grinding wheel is trimmed slightly less;

3. The rigidity of the workpiece itself is poor ;

4. On the grinding wheel, there are broken and too peeling sand particles and iron filings under the grinding of the workpiece accumulated on the surface of the grinding wheel. For this purpose, the dressed grinding wheel should be rinsed with cooling water or brushed clean;< /p>

5. The grinding wheel is not well dressed, and there are local bulges.

Fish scales appear on the surface

The main reason for the reappearance of fish scale marks on the surface is that the cutting edge of the grinding wheel is not sharp enough. The phenomenon of 'gnawing' occurs during grinding, and the vibration is large at this time, causing the workpiece.

The specific reasons for the fish scale marks on the surface are:

1. There are garbage and oil dirt on the surface of the grinding wheel;

2. The grinding wheel is not rounded;

3. The grinding wheel is dull. The dressing is not sharp enough;

4. The diamond fastener is not firm, the diamond is shaken or the quality of the diamond is not good and not sharp;

5. The hardness of the grinding wheel is uneven, etc.

Working surface roughening

The main reason for the reappearance of roughening marks on the surface is that after the coarse-grained abrasive particles fall off, the between the workpiece and the grinding wheel.

The specific reasons for the surface of the workpiece to be roughed during grinding are:

1. The traces left over during rough grinding are not removed during fine grinding ;

2. The coarse abrasive grains and tiny abrasive grains in the coolant are not filtered cleanly;

3. The abrasive grains are easy to fall off when the coarse-grained grinding wheel is just trimmed;

4. The toughness of the material is valid or the grinding wheel is too soft;

5. The toughness of the abrasive grains and the toughness of the workpiece material are not matched properly, etc.

There are straight wave marks on the surface of the workpiece

We cut a cross section of the vertical axis of the ground workpiece and enlarge it , it can be seen that its periphery is similar to a sine wave. If its center has no rotation and translation along the axis line, the trajectory around the sine wave is a waveform cylinder, which is also called a polygon.

The reason for the straight waveform is the movement of the grinding wheel relative to the workpiece or the periodic change of the grinding pressure of the grinding wheel on the workpiece, which causes vibration. This vibration may be forced vibration or self-excited vibration, so there are often more than one straight wave frequency on the workpiece.

The specific reasons for the straight waveform traces are:

1. The clearance of the grinding wheel spindle is too large;

2. The hardness of the grinding wheel is too high High;

3. The static balance of the grinding wheel is not good or the grinding wheel becomes dull;

4. The workpiece speed is too high;

5. The lateral knife is too large< /p>

6. The grinding wheel spindle bearing is worn out, and the fitting clearance is too large, resulting in radial runout;

7. The grinding wheel pressing mechanism or the worktable 'crawls

Reappearance of burn marks on the surface of the workpiece

The surface of the workpiece is often burned during the grinding process. There are several types of burns. One is that the burn is along the processing direction of the grinding wheel, and it is a dark black plaque; the other is that it is in the shape of lines or intermittent lines.

The surface of the workpiece is burnt during the grinding process for the following reasons:

1. The grinding wheel is too hard or the grain size is too fine and the tissue is too dense;< /p>

2. The feed rate is too large, the supply of cutting fluid is insufficient, and the heat dissipation conditions are poor;

3. The speed of the workpiece is too low, and the speed of the grinding wheel is too fast;

4 . The vibration of the grinding wheel is too large, and the grinding depth is constantly changing and burns;

5. The grinding wheel is not dressed in time or not well; Good;

7. The workpiece is burnt too deeply during rough grinding, and the fine grinding allowance is too small, so it is not ground off;

8. The workpiece clamping force or suction is insufficient, and the workpiece is not ground during grinding. Under the action of cutting force, the workpiece has the phenomenon of stalling and so on.

So how does the workpiece surface know if it is burnt during the grinding process? This can be checked by regular pickling.

After pickling the workpiece, when the surface is wet, it should be visually inspected under astigmatism immediately. The normal surface is uniform dark gray. If it is a software point, it will appear cloud-like dark black spots, and the perimeter is not fixed; if it is decarburized, it will appear gray or dark black mottled; if grinding cracks, the cracks will appear as cracks, such as burns, one is the surface along the surface. The machining direction of the grinding wheel presents dark black patches, and the second is the appearance of lines or intermittent lines.

If the above-mentioned burns occur during the grinding process, the reasons must be analyzed in time, and effective measures must be taken to solve them to prevent batch burns.