Hardware knowledge: detailed explanation of six polishing methods for abrasives

The 6 polishing methods of abrasive tools are as follows:

1. Mechanical polishing: Mechanical polishing is a polishing method that relies on the plastic deformation of the surface of the cutting material to remove the polished convexities to obtain a smooth surface. Generally, oilstone strips, wool wheels, sandpaper, abrasive belts, nylon wheels, etc. are used. Manual operation is mainly used. For special parts such as the surface of the rotating body, auxiliary tools such as turntables can be used. For high surface quality requirements, the method of ultra-precision polishing can be used. Ultra-precision polishing is an abrasive tool specially made with abrasives, which is pressed tightly on the processed surface of the workpiece in a polishing liquid containing abrasives for high-speed rotation. It 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 complicated equipment, 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.

3. Electrolytic polishing: The basic principle of electrolytic polishing is the same as that of chemical polishing, that is, it relies on the selective dissolution of small 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 macro leveling and micro leveling.

4. Ultrasonic polishing: Put the workpiece in the abrasive suspension and put it together in the ultrasonic field, relying on the oscillation effect of the ultrasonic, so that the abrasive is ground and polished on the surface of the workpiece. Ultrasonic machining has a small macroscopic 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 products on the surface of the workpiece are 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 carried by it to wash the surface of the workpiece to achieve the purpose of polishing. Common methods include: abrasive emery 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 good flowability under lower pressure and mixed with abrasives. The abrasives can be made of silicon carbide powder of abrasives.

6. Magnetic grinding and polishing: Magnetic grinding and polishing is the use of magnetic abrasives to form abrasive brushes 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 suitable abrasives, the surface roughness can reach Ra0.1μm.

The polishing mentioned in the processing of plastic molds is very different from the surface polishing required in other industries. Strictly speaking, the polishing of abrasive tools with abrasives should be called mirror finishing. It not only has high requirements for polishing itself, but also has high standards for surface flatness, smoothness and geometric accuracy. Surface polishing generally only requires a bright surface. The mirror processing of precision molds is still mainly mechanical polishing.