Mechanical polishing refers to the process of removing a thin layer of metal on the surface of the sample by means of rolling and grinding of very fine polishing powder.

If there are deep marks on the sample before polishing, it is difficult to remove it by mechanical polishing. Because it is necessary to discard the wear scar, it is necessary to thicken the polishing liquid. It takes more time or increases the pressure applied during polishing. This will cause the metal flow and disturbance on the sample surface, and the deformation layer of the sample wear surface is thickened. It makes the crystal phase in some alloys fall off. Especially when polishing aluminum alloy, because the hardness of the aluminum alloy is not large, the oxidation of the sample surface will be more severe, thereby affecting the observation of the structure. Therefore, the samples that are mechanically polished are only allowed to leave uniform fine grinding marks in a single direction after fine grinding.

Mechanical mirror polishing refers to the polishing and polishing of metal materials to achieve a flat, bright and mirror-like surface.

Polishing is carried out in order to obtain a smooth and smooth surface. At this time, very fine and uniform wear scars remained on the surface of the sample. Polishing is divided into fine grinding and rough grinding. The mechanical polishing process is to obtain a mirror-like surface treatment process. In many cases, the polishing wheel is used to repeatedly polish the very small unevenness on the surface of the sample, and then it is commonly used to modify the surface of the coating. Polishing is the last process on the surface of the sample or part. The purpose is to eliminate the fine grinding marks that remain on the surface of the sample after the polishing process. The ideal polished surface should be a mirror-like surface that is bright, smooth, no traces, no pits, reliefs, and no metal disturbance layers.

Mechanical polishing is divided into rough polishing, semi-precision polishing and fine polishing. Rough polishing is the surface after milling, electric spark, grinding and other processes can be selected from 35 000-40 000 rpm rotating surface polishing machine or ultrasonic grinding machine for polishing. Semi-precision polishing mainly uses sandpaper and kerosene. Precision polishing mainly uses diamond abrasive paste. The polishing process with an accuracy requirement of more than 1 μm can be performed in a clean polishing room in the mold processing workshop. For more precise polishing, an absolutely clean space is necessary. Dust, smoke, dandruff and saliva foam can all be scrapped after a few hours of high-precision polishing.