"Mirror surface processing", as the name implies, means that the processed surface can reflect images like a mirror. This level has reached a very good surface quality of the workpiece. Mirror surface processing can not only create a high "appearance" for the product, but also reduce the gap effect. Prolong the fatigue life of the workpiece; it is of great significance in many assembly and sealing structures. The polishing mirror surface processing technology is mainly used to reduce the surface roughness of the workpiece. When selecting the polishing process method for metal workpieces, different methods can be selected according to different needs. Common polishing mirror surface processing methods include: mechanical polishing, chemical polishing, electrolysis There are 7 kinds of polishing, Hawker mirror processing, ultrasonic polishing, fluid polishing and magnetic grinding and polishing.
1. Mechanical polishing
Mechanical polishing is a polishing method that removes the polished convex part by cutting and plastic deformation of the material surface to obtain a smooth surface. Generally, oil stone strips, wool wheels, sandpaper, etc. are used, and manual operations are mainly used. Special parts such as the surface of a rotating body can be polished. Using auxiliary tools such as turntables, ultra-fine grinding and polishing methods can be used for high surface quality requirements. Ultra-fine polishing uses a special abrasive tool, which is pressed against the surface of the workpiece to be processed in a polishing liquid containing abrasives for high-speed rotation. The surface roughness of Ra0.008μm can be achieved by using this technology, which is the highest among various polishing methods. Optical lens molds often use this method.
2. Chemical polishing
Chemical polishing is to make the microscopic convex part of the surface of the material dissolve preferentially compared with the concave part in the chemical medium, so as to obtain a smooth surface. The main advantage of this method is that it does not require complex equipment, can polish workpieces with complex shapes, and can polish many workpieces at the same time, with high efficiency. The core problem of chemical polishing is the preparation of polishing fluid. The surface roughness obtained by chemical polishing is generally several 10 μm.
3. Electropolishing
The basic principle of electrolytic polishing is the same as that of chemical polishing, that is, to make the surface smooth by selectively dissolving the tiny protrusions on the surface of the material. Compared with chemical polishing, it can eliminate the influence of cathode reaction, and the effect is better. The electrochemical polishing process is divided into two steps: (1) Macro leveling The dissolved product diffuses into the electrolyte, and the geometric roughness of the material surface decreases, Ra>1μm. (2) Twilight leveling Anode polarization, surface brightness is improved, Ra<1μm.
4. Hawker mirror processing equipment
As a new polishing process, it has unique advantages in processing many kinds of metal parts. It can replace traditional grinding machines, rolling, boring and rolling, honing, polishing machines, abrasive belt machines and other metal surface finishing equipment and processes; it makes it easy to process metal workpieces with a high finish. Hawker can not only polish, but also bring many additional benefits: it can improve the surface finish of the processed workpiece by more than 3 grades (the roughness Ra value can easily reach below 0.2); and the surface microhardness of the workpiece can be increased by more than 20% ; And greatly improved the surface wear resistance and corrosion resistance of the workpiece. Hawker can be used to process all kinds of stainless steel and other metal workpieces.
5. Ultrasonic polishing
The workpiece is put into the abrasive suspension and placed together in the ultrasonic field, and the abrasive is ground and polished on the surface of the workpiece by means of ultrasonic oscillation. Ultrasonic machining has a small macroscopic force and will not cause deformation of the workpiece, but it is difficult to manufacture and install tooling. Ultrasonic machining can be combined with chemical or electrochemical methods. On the basis of solution corrosion and electrolysis, ultrasonic vibration is applied to stir the solution, so that the dissolved products on the surface of the workpiece are separated, and the corrosion or electrolyte near the surface is uniform; the cavitation effect of ultrasonic waves in the liquid can also inhibit the corrosion process and facilitate surface brightening.
6. Fluid polishing
Fluid polishing relies on the high-speed flowing liquid and the abrasive particles carried to scour the surface of the workpiece to achieve the purpose of polishing. Commonly used methods are: abrasive jet processing, liquid jet processing, hydrodynamic grinding, etc. Hydrodynamic grinding is driven by hydraulic pressure, so that the liquid medium carrying abrasive particles flows back and forth across the surface of the workpiece at high speed. The medium is mainly made of a special compound (polymer-like substance) with good flowability under relatively low pressure and mixed with abrasives. The abrasives can be silicon carbide powder.
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7. Magnetic grinding and polishing
Magnetic grinding and polishing is to use magnetic abrasives to form abrasive brushes under the action of a magnetic field to grind the workpiece. This method has high processing efficiency, good quality, easy control of processing conditions and good working conditions. With suitable abrasives, the surface roughness can reach Ra 0.1μm. The polishing mentioned in plastic mold processing is very different from the surface polishing required in other industries. Strictly speaking, the polishing of molds should be called mirror processing. It not only has high requirements on the polishing itself but also has high standards on surface flatness, smoothness and geometric accuracy. Surface polishing is generally only required to obtain a bright surface. Because electrolytic polishing, fluid polishing and other methods are difficult to accurately control the geometric accuracy of parts, and the surface quality of chemical polishing, ultrasonic polishing, magnetic abrasive polishing and other methods cannot meet the requirements, so the mirror processing of precision molds is still based on mechanical polishing. host.
