The polishing process is mainly used to reduce the surface roughness of workpieces. When selecting the polishing process method for metal workpieces, different methods can be selected according to different needs. Today, I will share with you some common methods of polishing process.
1. Mechanical polishing
Mechanical polishing is a polishing method to obtain a smooth surface by removing the convex parts after polishing by cutting and plastic deformation of the material surface. Generally, oilstone strips, wool wheels, sandpaper, etc. are used. Manual operation is the main method. For special parts such as the surface of the rotary body, auxiliary tools such as turntables can be used. Ultra precision polishing can be used for those with high surface quality requirements. Ultra precision grinding and polishing is to use special abrasive tools, which are pressed against the machined surface of the workpiece in the grinding and polishing liquid containing abrasive materials to make high-speed rotation. With this technology, ra0.008 can be achieved μ M U.M is the highest among various polishing methods. This method is often used in optical lens molds.
2. Chemical polishing
Chemical polishing is to make the micro convex part of the surface of the material 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 require complex equipment, and can polish workpieces with complex shapes, and can polish many workpieces at the same time, with high efficiency. The core problem of chemical polishing is the preparation of polishing liquid. The surface roughness obtained by chemical polishing is generally 10 μ m。
Use of polishing machine
3. Electrolytic polishing
The basic principle of electrolytic polishing is the same as that of chemical polishing, that is, the surface is made smooth by selectively dissolving the small convex parts on the surface of the material. 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) Macro leveling: the dissolved product diffuses into the electrolyte, and the geometric roughness of the material surface decreases, RA > 1 μ m。
(2) . low light level and anode polarization, surface light brightness is improved, RA < 1 μ m。
4. Ultrasonic polishing
The workpiece is put into the abrasive suspension and placed in the ultrasonic field together, and the abrasive is ground and polished on the workpiece surface by the oscillation of the ultrasonic wave. The macro force of ultrasonic machining is small and will not cause workpiece deformation, 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 applied to stir the solution to separate the dissolved products on the surface of the workpiece, and the corrosion or electrolyte near the surface is uniform; The cavitation effect of ultrasonic wave in liquid can also inhibit the corrosion process, which is conducive to the surface brightness.
5. Fluid polishing
Fluid polishing relies on the high-speed flowing liquid and the abrasive particles carried by it to scour the workpiece surface to achieve the purpose of polishing. Common methods include abrasive jet machining, liquid jet machining, hydrodynamic grinding, etc. Hydrodynamic grinding is driven by hydraulic pressure to make the liquid medium carrying abrasive particles flow back and forth through the workpiece surface at high speed. The medium is mainly made of special compound (polymer like substance) with good flowability under low pressure and mixed with abrasive. The abrasive can be silicon carbide powder.
6. Magnetic abrasive polishing
Magnetic abrasive polishing is to use magnetic abrasive to form abrasive brush under the action of magnetic field to grind the workpiece. This method has high processing efficiency, good quality, easy control of processing conditions and good working conditions. With proper abrasive, the surface roughness can reach ra0.1 μ m。