1. Mechanical polishing: it is a polishing method to get a smooth surface by cutting and plastic deformation of the material surface to remove the convex part after polishing. It generally uses oilstone bar, wool wheel, sandpaper, etc. it is mainly operated by hand. If the surface quality requirements are high, it can use the ultra precision polishing method. Ultra precision lapping and polishing is a kind of special abrasive tool. In the lapping and polishing fluid containing abrasive, it is tightly pressed on the machined surface of aluminum alloy die casting to make high-speed rotary motion.
2. Chemical polishing: it is to make the micro protruding part of the surface of aluminum alloy die casting dissolve preferentially than 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 need complex equipment, and can polish aluminum alloy die castings with complex shape, and can polish many aluminum alloy die castings at the same time with high efficiency. The key problem of chemical polishing is the preparation of polishing solution. The surface roughness obtained by chemical polishing is generally 10 μ m。
3. Electropolishing: the basic principle is the same as chemical polishing, that is, the surface is smooth by selectively dissolving the tiny protrusions on the surface of the material. Compared with chemical polishing, the effect of cathode reaction can be eliminated and the effect is better.
4. Ultrasonic polishing: the aluminum alloy die casting parts are put into the abrasive suspension and placed together in the ultrasonic field, and the abrasive is ground and polished on the surface of the aluminum alloy die casting parts by the ultrasonic oscillation. Ultrasonic machining has small macro force and will not cause deformation of aluminum alloy die castings, but it is difficult to make and install tooling. Ultrasonic machining can be combined with chemical or electrochemical methods. On the basis of solution corrosion and electrolysis, ultrasonic vibration was applied to stir the solution to separate the dissolved products from the surface of aluminum alloy die casting, and the corrosion or electrolyte near the surface was uniform; The cavitation effect of ultrasonic in liquid can also inhibit the corrosion process, which is conducive to the surface lighting.
5. Fluid polishing: it relies on the high-speed flowing liquid and the abrasive particles carried by it to wash the surface of aluminum alloy die casting parts to achieve the purpose of polishing. The common methods are abrasive jet machining, liquid jet machining, hydrodynamic grinding and so on. Hydrodynamic grinding is driven by hydraulic pressure, which makes the liquid medium carrying abrasive particles flow through the surface of aluminum alloy die casting at high speed. The medium is mainly made of special compound (polymer like substance) with good flow property under low pressure and mixed with abrasive. The abrasive can be silicon carbide powder.
6. Magnetic abrasive polishing: it uses magnetic abrasive to form abrasive brush under the action of magnetic field to grind aluminum alloy die castings. This method has the advantages of high efficiency, good quality, easy control of processing conditions and good working conditions.
