The grinding method is divided into the following three categories according to the conditions of use of the abrasive:
1. For dry grinding, only a small amount of lubricating additive should be applied to the surface of the lap. As shown in Figure 8-12a. The sand is basically fixed on the lap during the grinding process, and its grinding action is mainly based on sliding grinding. This method is not high in productivity, but can achieve high processing accuracy and small surface roughness (ra 0.02 ~ 0.01 μm).
2. Wet Grinding The abrasive is applied to the lap during the grinding process and ground with dispersed sand. In addition to sand, the abrasive contains kerosene, engine oil, oleic acid, stearic acid and the like. During the grinding process, part of the sand is present between the lap and the workpiece, as shown in Figure 8-12b. At this time, the sand is mainly subjected to rolling grinding, and the productivity is high, and the surface roughness is 0.04 to 0.02 μm, which is generally used for roughing, but the processed surface is generally dull.
3, soft abrasive grinding
In the grinding process, the abrasive with chrome oxide as the abrasive is applied to the working surface of the rig. Since the abrasive is softer than the lap and the workpiece, the abrasive is suspended between the workpiece and the lap during the grinding process, mainly using the abrasive and the workpiece. The chemical action of the surface produces a very soft oxide film, and the film at the bumps is easily rubbed away by the abrasive. This method can obtain extremely fine surface roughness (ra 0.02 to 0.01 μm).
During the grinding process, there are dispersed fine-grained sand particles (abrasives and abrasives) between the lap and the surface of the workpiece to apply a certain pressure between them and cause complex relative motion, so that the sand is ground and ground. The chemical and physical effects of the agent remove a very thin layer on the surface of the workpiece to achieve a small surface roughness and high precision.