Usage and common problems of CBN grinding wheel
Nov 14 , 2019

CBN abrasive is a new abrasive developed in modern times. Due to its high hardness and micro-broken structure, it can achieve good efficiency for grinding high hardness steel.However, there are several problems in the use of CBN grinding wheel.The inner disc of most CBN grinding wheels is made of "metal".

While grinding the CBN grinding wheel, most of the heat energy will be transferred to the direction of the grinding wheel.Therefore, during the grinding process, heat energy will be continuously transferred to the grinding wheel.The metal disk then begins to expand as heat builds up.Because the distance between each position of the grinding wheel and the central grinding point of the heat source is different, the expansion degree of each position is also different, the true roundness of the grinding wheel is lost, and problems like "vibration" may occur!In addition, thermal expansion will also change the original set of feed.For example, the original setting of feeding amount is 0.01mm, but after thermal expansion, the feeding amount may become 0.03mm, so the dimensional accuracy is not easy to achieve.

Feeding problem caused by particle size differenceAs mentioned before, CBN abrasive is harder than the general abrasive, plus the shape is also more sharp, although the cutting force is good, but if you choose the same size as the general abrasive, the roughness of the grinding surface will become too coarse (close to the cutting effect).Therefore, in practice, the particle size of CBN is 3~4 orders smaller than that of ordinary grinding wheel. For example, if the particle size of ordinary grinding wheel is #80, CBN will choose #140 or #170.However, this increased the difficulty of feeding, because the appropriate amount of feeding is about1/10of the diameter of the grinding grain. When the selected particle size is small, the diameter of the grinding grain is also small, so the range of feeding is also reduced.

In addition to the initial difficulty of sharpening the knife, it is very easy to cause burns and other problems if the amount of knife is suddenly increased due to operating or machine problems.It also causes the phenomenon of grinding wheel thermal expansion mentioned above.In addition, CBN grinding wheel binder is stronger than ordinary grinding wheel, and its self-sharpening action is slow, which will make the situation worse.The solutionTo avoid these problems, many operators choose to "slow down the grinding wheel" to avoid burns and other problems.However, CBN has a micro-broken structure, and the slow speed is not conducive to giving full play to the characteristics and advantages of CBN, which will also reduce the grinding ratio and reduce the life of the grinding wheel.The other solution is to change the metal plate to other materials that do not expand due to temperature: such as ceramics.In order to solve the problem of metal inner disk expanding by heat and losing the true roundness.

Or you can also choose a new type of special containing a large number of blowhole binding agent BK: through the role of blowhole, to achieve the effect of heat dissipation.At the same time, because the contact area is reduced, the grinding resistance is reduced, and the grinding temperature is also decreased.
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