Bearings in the grinding process, the work surface is achieved by high-speed rotation of the grinding wheel, grinding so if you do not follow the operating instructions for operation and adjust the device, it will work in the bearing surface of various defects, which affects The overall quality of the bearing. Bearing in precision grinding, due to the rough demanding work surface grinding marks often appear to the naked eye can trace its surface grinding are the following.
Performance of cross spiral traces
This occurs mainly due to traces wheel bus straight poor, there is uneven phenomenon, in the grinding, the grinding wheel is only partial contact with the workpiece when the workpiece or the wheel back and forth several times after exercise, the performance will be reproduced in the workpiece cross helix, and can be observed visually. The pitch of the helix and the workpiece table speed, the size of workpiece speed, but also with the wheel axis is not parallel to the guide lines and the table.
(A) forming the main helix
1 Dresser bad, not chamfered corners, unused coolant to be trimmed;
2 table guide rail lubricant too much, resulting workbench floating;
3 machine precision is not good;
4 grinding pressure is too big.
(B) with the formation of helix causes
1.V shaped rail rigidity bad, when an offset grinding wheel, but wheel edge in contact with the work surface;
2 noisy wheel dressing table commutation speed is unstable, accuracy is not high, so that the edge of a grinding wheel dressing slightly less;
3. Workpiece itself rigidity;
4 wheel has broken too flaking grit and the workpiece grinding wheel under the iron plot attached to the surface, this should be a good dressing wheel with cooling water wash or scrub clean;
5 wheel dressing well, there are local projections and so on.
Surface appears scaly
Scaly surface reproduces the main reason is due to traces of grinding wheel cutting edge is not sharp enough, in the grinding occurs when "eating to live" phenomenon, when large vibration. Resulting in surface appears scaly traces of the specific reasons are:
A grinding wheel surface litter and oil thing;
2 Wheel untrimmed round;
3 wheel blunt. Dressing sharp enough;
4 fastening frame is not solid diamond, diamond or diamond quality is bad not shake sharp;
5 Wheel hardness uneven. Face nap
Surface scuffing marks reproduced mainly due to coarse grain shed, grain sandwiched between the workpiece and the grinding wheel and cause. Workpiece surface grinding was napping in the specific reasons are:
1 coarse grinding traces left behind, grinding when not worn;
2 coolant coarse grains and tiny grains filter is not clean;
3 coarse abrasive wheel just trimmed off easily when;
4 toughness validity or grinding wheel is too soft;
5 abrasive workpiece material toughness with toughness and improper
Workpiece surface has a direct waveform traces
We will milled workpiece cut a cross-section perpendicular axis line and zoom, you can see the surrounding approximately sinusoidal. So that the center line along the axis of rotation without translation, the track is the sine waveform around the cylinder, which is also known as a polygon. Generating direct wave because the wheel moves relative to the workpiece or the grinding wheel on the workpiece by cyclically changing pressure and vibration caused by the exigencies. This vibration may be forced vibration, it may be self-excited vibration, thus directly on the workpiece often more than one wave frequency. Direct waveform traces generated specific reasons are:
A grinding wheel spindle gap is too large;
2 Wheel hardness is too high;
3 wheel static balance wheel well or dull;
4. Workpiece speed is too high;
5 transverse Qi knife too;
6 wheel spindle bearing wear, the gap is too large, resulting runout;
7 wheel or bench pressing means "crawl" and so on.
Workpiece surface reproduction burns
Surface of the workpiece during the grinding process tends to burn, there are several types of burns, one burns machining direction along the wheel, dark black patches; Second, was the line or intermittent line shape. Workpiece surface grinding process of being burned, summed up in the following reasons:
1 wheel too hard or too fine granularity tissue too dense;
(2) Feed excessive cutting fluid supply, cooling conditions are poor;
3. Workpiece speed is too low, wheel speed too fast;
4 wheel runout is too large, constantly changing due to grinding depth and burn;
5 dresser dressing is not timely or bad;
6 diamond sharp dresser bad;
7. Workpiece coarse grinding burns too deep, grinding allowance is too small, no worn;
8 Workpiece clamping force or suction deficiencies in the grinding force, the workpiece stops phenomenon exists.
Then the workpiece surface in the grinding process of how to know if it works burned? This is accomplished by periodic acid to check it out. Workpiece after pickling, the surface is wet, should immediately astigmatism lamp visual inspection, the normal surface was uniformly dark gray. If so software point, showing dark clouds like black spots, and the entire perimeter uncertain; if decarbonization, is rendered dark gray or black piebald; if grinding cracks, the crack was cracked like, yes burns, one surface along Wheel machining direction showing dark black plaques, two lines are present or intermittent lines like. If the grinding process in the burn-in phenomenon, must promptly analyze the causes and take effective measures to solve them, to eliminate bulk burns.
Mainly the surface roughness
Bearing parts of the surface roughness of both standards and technical requirements, but in the processing and ultra-fine grinding process, for various reasons, often less than the specified requirements. Mainly the surface roughness caused mainly due to:
1 grinding speed is too low, too fast feed rate, feed excessive, no feed grinding time is too short;
2. Workpiece speed is too high or the workpiece axis and the wheel axis vibration is too large;
3 wheel size is too coarse or too soft;
4 wheel dresser too fast or trimming mechanism gap is too large;
5 diamond wheel dressing is not sharp or of poor quality;
6 ultra-fine oil stone quality is not good, the installation location is not correct;
7 ultra-precision quality is mainly kerosene;
8 ultra-precise time is too short;



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