xiehe model

What are the commonly used polishing methods for the production of aluminum alloy die castings?

Mechanical polishing

Mechanical polishing is a polishing method that obtains a smooth surface by cutting and removing the protruding parts produced by the plastic deformation of the material surface after polishing. Generally, whetstone strips, fur wheels, sandpaper, etc. are mainly operated manually. If high surface quality is required, ultra-precision polishing can be used.

Special abrasive tools are used for ultra-precision grinding and polishing in aluminum alloy die-casting production. In the grinding and polishing liquid containing abrasives, it is pressed against the processing surface and rotated at high speed. Using this technology can achieve a surface roughness of Ra0 008 μ M, which is the highest among various polishing methods, and is often used in optical lens molds.

Chemical polishing

Chemical polishing is to make the microscopic convex parts on the surface of aluminum alloy die castings dissolve in the chemical medium preferentially to the concave parts, so as to obtain a smooth surface. The main advantage of this method is that it does not require complex equipment, can polish aluminum alloy die castings with complex shapes, and can polish multiple aluminum alloy die castings 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 10 μm.

Electrolytic polishing

The basic principle of electropolishing is the same as that of chemical polishing, which is to make the surface smooth by selectively dissolving small protrusions on the surface of the material. Compared with chemical polishing, the effect of cathodic reaction can be eliminated, and the effect is better. The electrochemical polishing process is divided into two steps:

(1) After macro-leveling, the dissolved products diffuse into the electrolyte, and the surface geometric roughness of aluminum alloy die castings decreases, with RA > 1 μm.

(2) Low illumination level, anodic polarized light, improved surface brightness, RA < 1 μm.

Ultrasonic polishing

Put the aluminum alloy die casting into the abrasive suspension and put them together in the ultrasonic field. Relying on the vibration of ultrasonic waves, abrasives are ground and polished on the surface of aluminum alloy die castings. Ultrasonic processing has a 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 is used to stir the solution, so that the dissolved products on the surface of aluminum alloy die-casting parts 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. Good for bright surfaces.

Fluid polishing

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

Fluid power grinding is driven by hydraulic pressure, so that the liquid medium carrying abrasive particles flows back and forth at high speed on the surface of aluminum alloy die castings. The medium is mainly made of special compounds (polymer-like substances) with good fluidity under low pressure and mixed abrasives. The abrasive may be silicon carbide powder.

Magnetic grinding and polishing

Magnetic grinding and polishing is to use magnetic abrasives to form brushes under the action of a magnetic field to grind aluminum alloy die castings. The method has high processing efficiency, good quality, easy control of processing conditions and good working conditions. With appropriate abrasives, the surface roughness can reach Ra0 one micron.