When the vitrified CBN grinding wheel is grinding the workpiece at high speed, we often find that there will be burns on the workpiece surface. This is related to the vibration caused by the high-speed operation of the CBN grinding wheel and the breakage and burning of the CBN grinding wheel particles. The main types of workpiece burns are: linear or discontinuous linear burns, and black spot burns along the grinding direction of the grinding wheel.
So, what exactly causes the workpiece to burn during high-speed grinding with a vitrified CBN grinding wheel? Here are some points to summarize for you:
1. The hardness of the vitrified CBN grinding wheel is too high or the particles are too fine. Wrong selection of CBN abrasive applicability can also cause problems.
2. If the grinding wheel rotates too fast and the workpiece rotates too fast, it will also cause the workpiece to burn.
3. The cutting fluid supply is insufficient, the cutting feed rate is too large, and the heat dissipation conditions are poor.
4. Insufficient porosity of vitrified CBN grinding wheels is also one of the reasons.
5. If the ceramic bond CBN grinding wheel is not dressed in time, or the quality of cleaning the grinding wheel surface is not good, it is mainly because the ratio of dressing feed amount and rotation speed is not controlled well during dressing.
6. When ordering a grinding wheel with a diameter that is too large, the vibration of the base increases during use. Since the size and accuracy of each workpiece are different, if they are not subdivided, the grinding depth will continue to change, causing burns.
7. The machine tool bed steel is not strong enough, or the installation is not stable enough, causing resonance.
8. The clamping of the grinding workpiece is not firm enough, and the workpiece stops or moves out of position during grinding and cutting.
9. If the workpiece is burned too deeply during rough grinding and the reserve for fine grinding is too small, the burnt part of the workpiece will be seen if it is not ground away.
So, how can we tell whether the workpiece is burned? It is very simple. We can check it by regularly using acetone, alcohol, kerosene or pickling. For example, when the surface of the pickled workpiece is wet, we need to immediately conduct a visual inspection under a fluorescent light. Normal workpieces without burns are uniform dark gray.
If the workpiece is placed under a microscope for observation, it is obvious that the thin strips of rust-yellow color appearing on the surface of the workpiece are also a phenomenon of burns, and the blueing of the metal surface of the workpiece is also a burn.
CBN particle breakage, sand loss or burning can be observed under a microscope or felt by hand.
If the workpiece shows cracks or cracks, it is a grinding crack; If it shows grayish white or dark black spots, it is a decarbonization phenomenon; If there are soft spots, or dark cloud-like spots, and the roundness of the grinding wheel is not regular, it is a soft spot; If it is a burn, dark spots, continuous lines or discontinuous lines appear on the surface of the workpiece along the grinding direction of the grinding wheel, which is a burn phenomenon.
When grinding workpieces, if burns occur, the grinding wheel will also reduce its durability, and the general solution is dressing. Too frequent dressing will reduce the service life of the grinding wheel. To improve the durability of the vitrified CBN grinding wheel, the cause must be found in time and effective measures must be taken to analyze and solve it. Only in this way can qualified standard quality products be ground.
