Polishing

- Oct 16, 2019-

Polishing refers to the processing method of reducing the surface roughness of a workpiece by mechanical, chemical or electrochemical action to obtain a bright and smooth surface. It is a modification of the surface of the workpiece using polishing tools and abrasive particles or other polishing media. Polishing does not improve the dimensional accuracy or geometric accuracy of the workpiece, but rather for the purpose of smooth surface or specular gloss, and sometimes to eliminate gloss (extinction). Polishing wheels are often used as polishing tools. The polishing wheel is generally laminated with a plurality of layers of canvas, felt or leather, and is clamped on both sides by a metal circular plate, and the rim is coated with a polishing agent uniformly mixed with fine powder abrasive and grease. During polishing, the high-speed rotating polishing wheel (circumferential speed above 20 m / sec) is pressed against the workpiece, causing the abrasive to roll and micro-cut on the surface of the workpiece, thereby obtaining a bright machined surface with a surface roughness of Ra0.63. ~0.01 microns; when a non-greasy matting finish is used, the shiny surface can be matted to improve appearance. When mass producing bearing steel balls, the method of barrel polishing is often used. In the rough polishing, a large number of steel balls, lime and abrasive are placed in the inclined can-shaped drum. When the drum rotates, the steel ball and the abrasive are randomly rolled and collided in the cylinder to remove the surface convex surface and reduce the surface roughness. The purpose is to remove the margin of about 0.01 mm. In the case of fine polishing, steel balls and fur fragments are placed in the barrel, and continuous rotation for several hours gives a dazzling surface. The polishing of the precision ruler is carried out by immersing the processed surface in a polishing liquid, and the polishing liquid is prepared by mixing chrome oxide fine powder having a particle size of W5 to W0.5 and an emulsion. The polishing wheel is made of finely degreased wood or special fine felt. The movement track is uniform and dense mesh. The surface roughness after polishing is not more than Ra 0.01 μm. Observed under a microscope with 40 times magnification. Not any surface defects. In addition, there are methods such as electrolytic polishing.