1. Mechanical polishing

Mechanical polishing is a polishing method to obtain a smooth surface by cutting and removing the convex part after polishing due to plastic deformation of the material surface. Generally, oilstone strips, wool wheels, sandpaper, etc. are mainly operated manually. Ultra precision polishing can be used if the surface quality requirements are high.

Ultra precision lapping and polishing in aluminum alloy die casting production adopts special abrasive tools. In the lapping and polishing liquid containing abrasive, it is tightly pressed on the machined surface of aluminum alloy die casting for high-speed rotation. Ra0 can be achieved by using this technology 008 μ The surface roughness of M is the highest among various polishing methods, which is often used in optical lens molds. ​

2. Chemical polishing

Chemical polishing is to make the micro convex part of the surface of aluminum alloy die castings 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, can polish aluminum alloy die castings with complex shapes, and can polish many aluminum alloy die castings at the same time, with high efficiency. The core problem of chemical polishing is the preparation of polishing solution. The surface roughness obtained by chemical polishing is generally 10 μ m。

3. Electrolytic polishing

The basic principle of electropolishing is the same as that of chemical polishing, that is, the surface is smooth by selectively dissolving the small protruding parts on the surface of the material. Compared with chemical polishing, it can eliminate the influence of cathode reaction and has better effect. The electrochemical polishing process is divided into two steps:

(1) After macro leveling, the dissolved products diffuse into the electrolyte, the surface geometric roughness of aluminum alloy die castings decreases, RA > 1 μ m。

(2) The low light level is flat, the anode is polarized, the surface brightness is improved, RA < 1 μ m。

4. Ultrasonic polishing

The aluminum alloy die castings are put into the abrasive suspension and placed in the ultrasonic field together. Relying on the oscillation of ultrasonic, the abrasive is ground and polished on the surface of aluminum alloy die castings. The macro force of ultrasonic machining is small and will not cause the deformation of aluminum alloy die castings, but the tooling production and installation are difficult. 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 to separate the dissolved products on the surface of aluminum alloy die castings, and the corrosion or electrolyte near the surface is uniform; The cavitation effect of ultrasonic wave in liquid can also inhibit the corrosion process and is conducive to surface brightening.

5. Fluid polishing

Fluid polishing relies on the high-speed flowing liquid and its abrasive particles to wash the surface of aluminum alloy die castings to achieve the purpose of polishing. The common methods include abrasive jet machining, liquid jet machining, hydrodynamic grinding and so on.

Hydrodynamic grinding is driven by hydraulic pressure to make the liquid medium carrying abrasive particles flow back and forth through the surface of aluminum alloy die castings at high speed. The medium is mainly made of special compounds (polymer like substances) with good flowability under low pressure and mixed with abrasive. The abrasive can be silicon carbide powder.

6. Magnetic abrasive polishing

Magnetic abrasive polishing uses magnetic abrasive to form abrasive brush under the action of magnetic field to grind aluminum alloy die castings. This method has high processing efficiency, good quality, easy control of processing conditions and good working conditions. With appropriate abrasive, the surface roughness can reach Ra0 one μ m。