The key to operating a polishing machine is to try to achieve the maximum polishing rate so as to quickly remove the damage layer generated during grinding. At the same time, it's also important to ensure that the polishing damage layer does not affect the final observed structure, i.e., no false structures are created. The former requires using coarser abrasives to ensure a high polishing rate for removing the damage layer caused by grinding, but this will result in a deeper polishing damage layer; the latter requires using the finest materials to make the polishing damage layer shallower, but with a lower polishing rate.
The best way to resolve this contradiction is to divide the polishing process into two stages. The coarse polishing stage aims to remove the damage layer from grinding, and this stage should have the highest polishing rate possible. The surface damage caused by coarse polishing is secondary, though it should be minimized as much as possible. The next stage is fine polishing (or final polishing), which aims to remove the surface damage caused by coarse polishing and minimize the polishing damage. When polishing with a polishing machine, the sample grinding surface should be absolutely parallel to the polishing disc and evenly pressed lightly on it, taking care to prevent the sample from flying out or new scratches being formed due to excessive pressure. At the same time, the sample should rotate itself and move back and forth along the radius direction of the disc to avoid the local wear of the polishing cloth becoming too fast. During the polishing process, micro-powder suspension should be continuously added to keep the polishing cloth at a certain humidity. If the humidity is too high, it will weaken the scratch effect of polishing, causing hard phases in the sample to appear protruding and non-metallic inclusions in steel and graphite phases in cast iron to produce "dragging tails". If the humidity is too low, the friction heat will cause the sample temperature to rise, reducing the lubrication effect, making the ground surface lose its luster, even forming black spots. For light alloys, it may cause surface damage. To achieve the purpose of coarse polishing, the speed of the disc should be relatively low, preferably not exceeding 600 r/min; the polishing time should be longer than the time needed to remove scratches because it is also necessary to remove the deformed layer. After coarse polishing, the surface is smooth but dull, and under a microscope, there are uniform and delicate scratches that need to be eliminated by fine polishing.
During fine polishing, the disc speed can be appropriately increased, and the polishing time should be enough to remove the damage layer caused by coarse polishing. After fine polishing, the surface is bright like a mirror, and under the conditions of a bright-field microscope, no scratches can be seen, but under phase contrast illumination, scratches can still be observed. The quality of polishing significantly affects the structure of the sample and has gradually attracted the attention of relevant experts. In recent years, both domestically and internationally, a lot of research work has been done on the performance of polishing machines, developing many new models and new generations of polishing equipment. These are evolving from manual operation into various semi-automatic and fully automatic polishing machines.
Below, we introduce the performance and characteristics of several commonly used mechanical polishers. Polishing machines are specifically designed for effect treatment on the surfaces and tubes of metal products such as steel, aluminum, copper, etc. Dozens of original accessories meet different needs, easily producing various precision snow patterns, brushed textures, wave patterns, matte finishes, mirror finishes, etc. They can quickly repair deep scratches and minor scratches, quickly grind and polish; they handle weld seams, water gate marks, oxide films, stains, and paint, suitable for deburring, rounding corners, decorative metal processing, without creating shadows, transition zones, and uneven decorative surfaces during processing, making them important equipment in metal product production lines. Polishing machines are suitable for industries such as wood, furniture (e.g., flat wooden boards, furniture metal handles, etc.), hardware (metal) materials and products including aluminum profiles and their products, stainless steel products and utensils, copper profiles and their products, water heating sanitary ware, locks, lighting fixtures, signboards, hardware craft decorations, knives, door hinges, automotive and bicycle parts, tableware, buckle products, buttons, belt buckles, mobile phone cases, watchmaking industry, etc. They are also applicable to electronic components, electronic devices such as electronic components, plate sanding and brushing, etc.