Gear lapping is a traditional process. It is a method of micro removal of workpiece surface with free abrasive particles and grinding tool, which can obtain very low surface roughness. It belongs to gear finishing and has the characteristics of low cost. When the gear processing is not out of tolerance or the heat treatment deformation is small, it can reduce the roughness of the effective tooth profile, reduce the gear transmission noise, and properly correct the position of the contact area of the tooth surface, but it can not eliminate the radial runout, pitch error, tooth profile error and other errors caused by heat treatment deformation. Moreover, after grinding, the abrasive particles are difficult to be completely eliminated, which will inevitably reduce the wear resistance of the gear in use.

High machining accuracy can be obtained by gear grinding. For some spiral bevel gears with high precision requirements, it is still the only means. It can not only reduce the tooth surface roughness and transmission noise, but also improve the contact accuracy and motion accuracy of the gear. However, during the grinding of hard tooth surface, the grinding force is large, the temperature in the grinding area is high, and the grinding heat is mostly transmitted to the gear, resulting in the thermal effect of grinding, which has a great impact on the surface quality and service performance of the gear, often causing thermal damage (surface oxidation, burn and crack) on the gear surface, reducing the service life and working reliability of the gear. Moreover, the machining stability of grinding is poor, coupled with low efficiency and high energy consumption. In order to solve the above problems, CBN grinding wheel grinding method has been developed abroad in recent years. CBN grinding wheel has a series of advantages such as high hardness, good wear resistance, high service life, good precision retention, good cutting performance, high metal removal rate, less burns and cracks on the ground surface, more compressive stress on the surface and good surface quality. It is becoming the development direction of gear grinding and finishing on hard tooth surface

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