CBN abrasive is a new abrasive developed in recent years. Due to its high hardness and micro-crushed structure, it can achieve good efficiency in grinding high-hardness steel. However, the CBN grinding wheel needs to pay attention to several problems in its use.
Most of the CBN grinding wheel inner discs are made of metal, and when the CBN grinding wheel is ground, most of the heat energy is transmitted to the grinding wheel. Therefore, during the grinding process, heat is continuously transferred to the grinding wheel. The metal inner disk begins to expand due to the accumulation of heat.
Because the distance between the grinding wheel and the grinding point of the heat source center is different, the degree of expansion of each azimuth is also different. The roundness of the grinding wheel is lost, and vibration and other problems may occur! The expansion of the metal inner disk will also make the original setting. The amount of feed changes. For example, the original feed amount is 0.01mm, and the feed amount after thermal expansion may become 0.03mm, and the size is not accurate.
CBN abrasives are harder than general abrasives, and the shape is sharper. Although the cutting force is good, if the same grain size is selected as the general abrasive, the roughness of the polished surface will become too thick (close to the cutting effect). Therefore, the particle size selection of CBN will be 3~4 steps thinner than the general grinding wheel. For example, the general grinding wheel has a particle size of #80, and CBN will select #140 or #170. However, this increases the difficulty of the feed. Since the appropriate feed rate is about 1/10 of the diameter of the abrasive grain, when the selected particle size is small, the diameter of the abrasive grain is also small, and the size of the feed amount is also reduced.
In addition to the difficulty of the knife at the beginning, if the amount of the feed is suddenly increased due to the operation or the problem of the machine, it is very simple to cause burns and other problems. It also leads to the phenomenon of thermal expansion of the grinding wheel mentioned above. In addition, the CBN grinding wheel binder is stronger than the general grinding wheel, and the self-sharpening effect is slow, which will make this situation worse.
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