In the process of grinding, under the action of friction and extrusion, the edges and corners of the grinding wheel are gradually rounded and blunt, or when grinding the ductile materials, the grinding chips are often embedded in the pores of the grinding wheel surface, so that the surface of the grinding wheel is blocked, and finally the cutting ability of the grinding wheel is lost. At this time, there will be slip between the grinding wheel and the workpiece, which may cause vibration and noise, reduce the grinding efficiency and reduce the surface roughness. At the same time, due to the increase of grinding force and grinding heat, it will cause working deformation and affect grinding accuracy, and even cause burns and small cracks on the grinding surface. In addition, due to the uneven hardness of the grinding wheel and the different working conditions of the abrasive particles, the working surface of the grinding wheel is worn unevenly, and the number of the abrasive particles in each part varies, resulting in the loss of the contour viscosity of the grinding wheel, which affects the shape accuracy and surface roughness of the workpiece surface.

 

Grinding wheel dressing method:

 

Grinding wheel dressing generally includes turning, using diamond roller, grinding and rolling. ① turning and dressing method: single diamond (or diamond pen and diamond dressing block made of fine diamond) is the most commonly used dressing method (Fig. 1). The diamond cutter installed on the tool holder usually inclines about 5 ° - 15 ° in both vertical and horizontal directions; the contact point between the diamond and the grinding wheel should be 0.5-2 mm lower than the axis of the grinding wheel. During dressing, the diamond should move at a uniform low speed. It is required that the smaller the surface roughness after grinding, the lower the feed speed. If the surface roughness of ra0.16-0.04 μ m is to be achieved, the dressing feed speed shall be less than 50 mm / min. The total trimming amount is generally about 0.1mm on one side, and it is repeatedly trimmed. The cutting depth of rough trimming is 0.01-0.03 mm each time, and that of fine trimming is less than 0.01 mm. ② diamond roller dressing method: a large number of diamond particles are inlaid on the surface of the steel roller by electroplating or powder metallurgy (Figure 2). The diamond roller rotates at a certain speed (to reduce the relative speed of the roller and the grinding wheel), which produces grinding and rolling effects on the surface of the high-speed rotating grinding wheel, so that the grinding wheel can obtain a sharp working surface which is consistent with the roller profile. The diamond roller has complex manufacturing and high cost, but it is durable and has high dressing efficiency. It is suitable for dressing and grinding special shaped surfaces (such as thread, gear and turbine blade tenon) in mass production. ③ grinding and dressing method of grinding wheel: the ultra-hard silicon carbide grinding wheel with low-speed rotation and the grinding wheel with high-speed rotation are used for the purpose of dressing. (4) roll dressing method: use hard alloy disk, a group of rollers made of wave shaped white iron disk or hardened steel plate with groove to finish roll and extrusion with grinding wheel. Generally, the roller is installed on the trimming fixture for manual operation, which has high trimming efficiency and is suitable for the trimming of rough grinding wheel.