Cross spiral traces appear on the surface The reason for this kind of trace is mainly due to the poor straightness of the generatrix of the grinding wheel and the existence of unevenness. During grinding, the grinding wheel and the workpiece are only in partial contact. Helical and visible to 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, and is also related to the non-parallel relationship between the axis of the grinding wheel and the guide rail of the worktable. ►The main reason for the formation of the helix 1. The grinding wheel is poorly dressed, the corners are not chamfered, and no coolant is used for dressing; 2. There is too much lubricating oil in the guide rail of the workbench, causing the workbench to float; 3. The accuracy of the machine tool is not good; 4. Excessive grinding pressure, etc. ►Specific reasons for the formation of the helix 1. The rigidity of the V-shaped guide rail is not good. When grinding, the grinding wheel is offset, but the edge of the grinding wheel is in contact with the working surface; 2. When dressing the noisy wheel, the reversing speed of the worktable is unstable and the precision is not high, so that the dressing of a certain edge of the grinding wheel is slightly less; 3. The rigidity of the workpiece itself is poor; 4. There are broken and peeled sand grains on the grinding wheel and iron filings from the grinding of the workpiece are accumulated on the surface of the grinding wheel. For this reason, the repaired grinding wheel should be washed or brushed with cooling water; 5. The dressing of the grinding wheel is not good, and there are local protrusions, etc. Fish scales appear on the surface The main reason for reappearing fish scale marks on the surface is that the cutting edge of the grinding wheel is not sharp enough, and the phenomenon of “gnawing” occurs during grinding, and the vibration is large at this time, resulting in workpieces. ►The specific reasons for fish scale marks appearing on the surface are: 1. Garbage and oil dirt on the surface of the grinding wheel; 2. The grinding wheel is not rounded; 3. The grinding wheel becomes dull. The trimming is not sharp enough; 4. The diamond fastening frame is not firm, the diamond shakes or the quality of the diamond is not sharp; 5. Uneven hardness of the grinding wheel, etc. Working surface roughening The main reason for the reappearance of rough marks on the surface is that after the coarse-grained abrasive grains fall off, the abrasive grains are sandwiched between the workpiece and the grinding wheel. ►The specific reasons why the workpiece surface is roughened during grinding are: 1. The marks left over from rough grinding are not removed during fine grinding; 2. Coarse abrasive particles and tiny abrasive particles in the coolant are not filtered cleanly; 3. When the coarse-grained grinding wheel is just dressed, the abrasive grains are easy to fall off; 4. The validity period of the material toughness or the grinding wheel is too soft; 5. Improper coordination between abrasive grain toughness and workpiece material toughness, etc. There are straight wave traces on the surface of the workpiece We cut a cross-section of the center line of the vertical axis of the ground workpiece and enlarge it, and we can see that its periphery is similar to a sine wave. Make its center along the axis without rotation and translation, the track around the sine wave is the waveform cylinder, also known as polygon. The reason for the straight waveform is that the movement of the grinding wheel relative to the workpiece or the periodic change of the pressure of the grinding wheel on the workpiece grinding causes vibration. This kind of vibration may be forced vibration or self-excited vibration, so there are often more than one direct wave frequency on the workpiece. ►Specific reasons for a straight waveform trace are: 1. The clearance of the grinding wheel spindle is too large; 2. The hardness of the grinding wheel is too high; 3. The static balance of the grinding wheel is not good or the grinding wheel is blunt; 4. The workpiece speed is too high; 5. The horizontal knife is too big 6. The bearing of the grinding wheel spindle is worn, and the matching clearance is too large, resulting in radial runout; 7. Grinding wheel pressing mechanism or table “crawling”, etc. The surface of the workpiece reproduces burn marks The surface of the workpiece is often burned during the grinding process. There are several types of burns. One is that the burns are along the processing direction of the grinding wheel and appear as dark black spots; the other is that the burns are in the form of lines or intermittent lines. ►The surface of the workpiece is burned during the grinding process for the following reasons: 1. The grinding wheel is too hard or the grain size is too fine and the structure is too dense; 2. The feed rate is too large, the supply of cutting fluid is insufficient, and the heat dissipation condition is poor; 3. The rotation speed of the workpiece is too low and the rotation speed of the grinding wheel is too fast; 4. The vibration of the grinding wheel is too large, causing burns due to the continuous change of the grinding depth; 5. The dressing of the grinding wheel is not timely or the dressing is not good; 6. The diamond is sharp and the grinding wheel is not well dressed; 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 clamping force or suction force of the workpiece is insufficient, and the workpiece stops rotating under the action of the grinding force. So how do you know whether the surface of the workpiece is burnt during the grinding process? This can be checked by regular pickling. After the workpiece is pickled, when the surface is wet, it should be visually inspected under the astigmatism light immediately, and the normal surface is uniform dark gray. If it is a soft spot, it will appear cloud-like dark black spots, and the perimeter is irregular; if it is decarburized, it will appear grayish white or dark black mottled; The processing direction of the grinding wheel presents dark black plaques, and the second presents lines or intermittent lines. If the above-mentioned burn phenomenon occurs during the grinding process, the cause must be analyzed in time, and effective measures should be taken to solve it, so as to prevent batch burns. The surface roughness does not meet the requirements There are standards and technological requirements for the surface roughness of bearing parts, but in the process of grinding and superfinishing, due to various reasons, they often fail to meet the specified requirements. ►The main reasons for the surface roughness of the workpiece not meeting the requirements are: 1. The grinding speed is too low, the feed rate is too fast, the feed amount is too large, and the grinding time without feed is too short; 2. The rotating speed of the workpiece is too high or the vibration of the workpiece shaft and the grinding wheel shaft is too large; 3. The grain size of the grinding wheel is too coarse or too soft; 4. The dressing speed of the grinding wheel is too fast or the clearance of the dressing mechanism is too large; 5. The diamond for dressing the grinding wheel is not sharp or of poor quality; 6. The quality of the oilstone used for ultra-finishing is not good, and the installation position is not correct; 7. The quality of kerosene for ultra-finishing cannot meet the requirements; 8. Superfine time is too short, etc.