The key to operating a polishing machine is to achieve the maximum polishing rate in order 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 microstructure, i.e., it should not cause false structures. The former requires the use of coarser abrasives to ensure a high polishing rate for removing the damage layer caused by grinding, but this results in a deeper polishing damage layer; the latter requires the finest materials, which produce a shallower polishing damage layer but have a lower polishing rate.
The best way to resolve this contradiction is to divide the polishing process into two stages. The first stage, coarse polishing, aims to remove the damage layer from grinding. This stage should have the highest polishing rate, and while the surface damage caused by coarse polishing is secondary, it should still be minimized as much as possible. The second stage is fine polishing (or final polishing), which aims to remove the surface damage caused by coarse polishing and minimize the polishing damage. During polishing, the sample grinding surface should be parallel to the polishing disc and lightly and evenly pressed onto it, taking care to prevent the sample from flying out or generating new scratches due to excessive pressure. Additionally, the sample should rotate on its own axis and move back and forth along the radius of the rotating disc to avoid excessive wear on localized areas of the polishing cloth. During the polishing process, micropowder suspension should be continuously added to maintain a certain level of humidity on the polishing cloth. Excessive humidity can weaken the scratch-removal effect, causing hard phases in the sample to appear raised and non-metallic inclusions in steel or graphite in cast iron to exhibit "tail-dragging" phenomena. Insufficient humidity, on the other hand, causes frictional heat to raise the temperature of the sample, reducing lubrication, losing gloss on the ground surface, and even causing black spots. In the case of light alloys, this may result in surface damage.
To achieve the goal of coarse polishing, the rotation speed of the disc should be relatively low, preferably not exceeding 600 rpm/min. Polishing time should be longer than what is required to remove scratches, as deformation layers also need to be removed. After coarse polishing, the surface appears smooth but dull, with uniform and fine scratches observable under a microscope, which require further elimination through fine polishing.
During fine polishing, the disc speed can be appropriately increased, and the polishing time should be sufficient to remove the damage layer from coarse polishing. After fine polishing, the surface will be bright like a mirror, and no scratches will be visible under a microscope in bright-field conditions, though they may still be seen under phase-contrast illumination. The quality of polishing significantly affects the microstructure of the sample and has gradually drawn attention from relevant experts. In recent years, extensive research has been conducted both domestically and internationally on the performance of polishing machines, leading to the development of many new models and a new generation 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 polishing machines. These machines are specifically designed for surface treatment of metal products such as steel, aluminum, copper, and tubes. They offer dozens of original accessories to meet different needs, effortlessly creating various finishes such as snowflake patterns, brushed textures, wave patterns, matte surfaces, and mirror finishes. They can quickly repair deep scratches and minor abrasions, polish weld seams, water marks, oxide films, stains, and paint, form rounded edges, and perform decorative metal processing without creating shadows, transition zones, or uneven decorative surfaces. These machines are essential equipment in metal product production lines.
Polishing machines are suitable for the following industries: wood and furniture industry, such as sanding and brushing wooden boards and metal handles for furniture; hardware (metal) materials and products, including aluminum profiles and their products, stainless steel products and utensils, copper profiles and their products, plumbing fixtures, locks, lighting fixtures, nameplates, hardware crafts, knives, hinges for doors, automotive and bicycle components, cutlery, button and buckle products, buttons, belt buckles, mobile phone casings, watchmaking industry, etc., for sanding and brushing workpieces; electronic parts and devices, such as electronic parts, flat sanding and brushing, etc.