Application of CBN grinding wheel in bearing grinding

CBN grinding wheel can solve the cutting of high hardness materials. The application of CBN grinding wheel in the processing operation can not only reduce energy consumption, but also greatly improve the work efficiency, so it is widely used in the current processing operation. 

1. CBN is a hardness material second only to diamond. It not only has the excellent performance of diamond, but also has higher stability, so it is widely used in the processing and manufacturing industry. Based on the characteristics of high heat resistance and high sensitivity of CBN material, CBN wheel in bearing processing, its thermal stability and thermal conductivity is good, can work normally in 1300~1560℃ high temperature, suitable for high strength alloy steel and high speed steel grinding process with high thermal sensitivity, and can keep the material smooth, will not leave grinding cracks.

Vitrified bond CBN grinding wheel is based on CBN grinding wheel technology through technical improvement, its stability, heat resistance and acid and alkali resistance is strong, in the process of working, its coefficient of thermal expansion is small, not easy to clog, so it can keep the surface of the material smooth.

2. Application of CBN grinding wheel in bearing grinding

In bearing processing, grinding of raceway of outer ring and inner diameter of inner ring is an important process in bearing grinding.The performance and cooling condition of grinding wheel are affected by the size of inner hole of grinding wheel. The high rigidity of CBN grinding wheel and the high-power motorized spindle can reduce the wear of grinding wheel surface, improve the efficiency of processing operation, and greatly improve the size, quality and accuracy of grinding workpiece.

(1) Grinding machine

The grinding machine undertakes the main work of grinding, its high rigidity, high power characteristics can quickly and accurately remove the metal allowance. At the same time, due to the low wear degree of CBN grinding wheel, although the equipment investment in the early stage is large, it can be used repeatedly for a long time and the economy is good. In CBN grinding wheel, if diamond dresser is used, the wire speed of dresser and grinding wheel should be controlled within a certain range by controlling the drive frequency conversion power supply.

(2) CBN grinding wheel dressing

In the use of CBN grinding wheel, when the wear of grinding wheel width direction exceeds 80% of the total width of grinding wheel, the grinding wheel should be dressed. The dressing amount of grinding wheel is generally 0.01mm/ time, so the dressing method can be adopted by stages. CBN grinding wheel dressing mainly includes shaping and sharpening. The so-called shaping means that the grinding wheel keeps its original precision and geometric shape through dressing. The so-called sharpening refers to removing the binding agent contained in the grinding wheel grains, so that the grains have a certain height difference, so as to form a cutting surface, so as to facilitate bearing grinding. 

CBN grinding wheel dressing is generally done by grinding and dressing diamond rollers. The advantage of this method is that the production efficiency is high, and the dressing time only needs 2~ 10s. CBN grinding wheel dressing can also be carried out in the bearing processing operation at the same time, without affecting the normal working status of grinding operation. The surface quality of dressed CBN grinding wheel is better because of the higher precision of diamond wheel.

(3) CBN grinding wheel cooling

In the grinding process, the linear speed of CBN grinding wheel can reach 100m/s, so as to ensure better grinding efficiency.

Due to the high linear velocity, there is a strong friction and cutting heat, which will affect the quality of bearing processing. In bearing grinding process, therefore, should be coolant injection of CBN grinding wheel, it can not only to the CBN grinding wheel and related artifacts for cooling, can also in the grinding wheel and bearings have very good lubrication effect of workpiece, and the adsorption effect of oil film itself, to form a protective layer on the surface of bearing, to prevent the oxidation of bearing, ensure the bearing to stay after processing.

The main components of the coolant used in CBN grinding wheel cooling are a kind of light mineral oil and anti-rust additives. Oil additives are often added in the processing operation to ensure the lubrication effect of CBN grinding wheel in the processing process. The cooling of CBN grinding wheel is generally done by injection method, which has a certain effect on the high-speed rotation of grinding wheel through high supply acceleration, and quickly takes away the heat generated in grinding, so that the grinding fluid of grinding wheel can enter the grinding zone smoothly and improve the grinding effect of grinding wheel.

CBN grinding wheel cooling can not only prolong the service life of grinding wheel, but also improve the grinding cutting effect of grinding wheel. In the process of grinding wheel cooling, coolant recoil is carried out at the same time to wash the surface of grinding wheel and remove the impurities in the grinding process, which can effectively prevent the blockage of grinding wheel and improve the quality of workpiece grinding wheel. 

Among the previous grinding wheel cooling methods, internal cooling method is generally adopted. Its principle is to make the grinding fluid enter the grinding wheel through the side of the wheel through the pore of the grinding wheel, and eliminate the grinding fluid from the pore with the centrifugal rate of high speed rotation, so that the available grinding fluid re-enters the grinding zone and ensures the normal operation of the grinding wheel. Due to the small porosity of grinding wheel, the grinding fluid must be precisely filtered in order to enter the grinding wheel smoothly through the pore. In the grinding process, the grinding wheel will produce a lot of impurities, resulting in the reduction of the purity of the grinding fluid, which may cause the corrosion and damage of the grinding fluid, not only resulting in the reduction of the machining quality of the grinding workpiece, but also affect the environmental health, and cause great damage to the grinding wheel.

(4) Electrical control

CBN grinding wheel needs some power support in grinding process. In order to improve the quality of the grinding workpiece, strengthen the electrical control, so that it can meet the best results of the grinding operation. CBN grinding wheel will be affected by various factors in the process of grinding, and then have an effect on the quality of the grinding workpiece. For example, after the dressing of CBN grinding wheel, there will generally be a relatively unstable period, at this time, it is necessary to adjust the feed speed of the machine tool appropriately, and use CNC control to adapt to the working state of CBN grinding wheel.

---EDITOR: Doris Hu

---POST: Doris Hu