What are the polishing methods for metal parts?

At present, the common polishing methods of metal parts are as follows:

1. Mechanical polishing
Mechanical polishing is a polishing method that relies on cutting and plastic deformation of the material surface to remove the polished protrusions to obtain a smooth surface. Generally, oil stone sticks, wool wheels, sandpaper, etc. are used, and manual operations are the main method. Special parts such as the surface of the rotating body can be used. Using auxiliary tools such as turntables, ultra-precision polishing can be used for those with high surface quality requirements. Ultra-precision polishing is the use of special abrasive tools, which are pressed against the processed surface of the workpiece in a polishing liquid containing abrasives for high-speed rotation. With this technology, the surface roughness of Ra0.008um can be reached, which is the highest among various polishing methods. Optical lens molds often use this method.

2. Chemical polishing
Chemical polishing is to make the surface microscopic convex part of the material in the chemical medium dissolve preferentially than the concave part, 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 ,efficient. The core problem of chemical polishing is the preparation of polishing liquid. The surface roughness obtained by chemical polishing is generally several 10um.

3. Electrolytic polishing
The basic principle of electrolytic polishing is the same as that of chemical polishing, that is, by selectively dissolving tiny protrusions on the surface of the material to make the surface smooth. Compared with chemical polishing, the effect of cathode reaction can be eliminated, and the effect is better. The electrochemical polishing process is divided into two steps: (1) Macroscopic leveling: the dissolved products diffuse into the electrolyte, and the geometric roughness of the material surface decreases. (2) Micro leveling: anodic polarization, surface brightness is improved.

4. Ultrasonic polishing
Put the workpiece in the abrasive suspension and put it together in the ultrasonic field, relying on the vibration of the ultrasonic to make the abrasive grind and polish on the surface of the workpiece. Ultrasonic machining has a small macro force and will not cause deformation of the workpiece, but it is difficult to manufacture and install tooling. Ultrasonic processing 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 product on the surface of the workpiece is separated, and the corrosion or electrolyte near the surface is uniform; the cavitation effect of ultrasonic in the liquid can also inhibit the corrosion process and facilitate surface brightening.

5. Fluid polishing
Fluid polishing relies on high-speed flowing liquid and the abrasive particles it carries; scouring the surface of the workpiece to achieve the purpose of polishing. Commonly used methods are: abrasive jet processing, liquid jet processing, hydrodynamic grinding and so on. Hydrodynamic grinding is driven by hydraulic pressure to make the liquid medium carrying abrasive particles flow back and forth across the surface of the workpiece at high speed. The medium is mainly made of special compounds with better flowability under lower pressure and mixed with abrasives. The abrasives can be made of silicon carbide powder.