Introduction To Several Common Polishing Methods

1.1 Mechanical polishing Mechanical polishing is a polishing method that relies on cutting and plastic deformation of the material surface to remove the polished convex parts to obtain a smooth surface. Generally, oilstone strips, wool wheels, sandpaper, etc. are used. Mainly manual operations, special parts such as rotary bodies For the surface, auxiliary tools such as turntables can be used. For those with high surface quality requirements, ultra-precision grinding and polishing can be used. Super-precision polishing uses special abrasives, which are pressed against the surface of the workpiece to be processed in a polishing fluid containing abrasives to perform high-speed rotation. This technology can achieve a surface roughness of Ra0.008μm, which is the highest among various polishing methods. This method is often used for optical lens molds.
1.2 Chemical polishing Chemical polishing allows the microscopic convex parts of the surface of the material to be dissolved preferentially in the chemical medium than the concave parts, thereby obtaining a smooth surface. The main advantage of this method is that it does not require complicated equipment, can polish workpieces with complex shapes, and can polish many workpieces at the same time, with high efficiency. The core issue of chemical polishing is the preparation of polishing fluid. The surface roughness obtained by chemical polishing is generally several 10 μm.
1.3 Electrolytic polishing The basic principle of electrolytic polishing is the same as chemical polishing, that is, it relies on selective dissolution of tiny protrusions on the surface of the material to make the surface smooth. Compared with chemical polishing, the influence 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, Ra>1μm. (2) Glimmer and smooth: Anodic polarization improves surface brightness, Ra<1μm.
1.4 Ultrasonic polishing: Put the workpiece into the abrasive suspension and place it together in the ultrasonic field. Relying on the oscillation of ultrasonic waves, the abrasives grind and polish the surface of the workpiece. The macro force of ultrasonic processing is small and will not cause deformation of the workpiece, but the production and installation of tooling is difficult. 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 to separate the dissolved products from the surface of the workpiece and make the corrosion or electrolyte near the surface uniform; the cavitation effect of ultrasonic waves in the liquid can also inhibit the corrosion process and facilitate surface brightening.
1.5 Fluid polishing Fluid polishing relies on high-speed flowing liquid and the abrasive particles it carries to wash away the surface of the workpiece to achieve the purpose of polishing. Commonly used methods include: abrasive jet machining, liquid jet machining, fluid power grinding, etc. Fluid power grinding is driven by hydraulic pressure, which causes the liquid medium carrying abrasive particles to flow back and forth across the workpiece surface at high speed. The medium is mainly made of special compounds (polymer-like substances) with good flow properties under lower pressure and mixed with abrasives. The abrasives can be silicon carbide powder.
1.6 Magnetic grinding and polishing Magnetic grinding and polishing uses magnetic abrasives to form an abrasive brush 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. Using appropriate abrasives, the surface roughness can reach Ra0.1μm.