1. Mechanical polishing: Mechanical polishing is a polishing method that removes the polished convex part by plastic deformation of the surface of the cutting material to obtain a smooth surface. Generally, oil stone strips, wool wheels, sandpaper, abrasive belts, nylon wheels, etc. are used. Mainly, for special parts such as the surface of the rotary body, auxiliary tools such as turntables can be used, and the method of ultra-fine grinding and polishing can be used for high surface quality requirements. Ultra-fine polishing is a special grinding tool made of abrasives, which is pressed against the surface of the workpiece to be processed in the 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 microscopic protruding part of the surface of the material dissolve preferentially compared with 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, 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 fluid.
3. Electrolytic polishing: The basic principle of electrolytic polishing is the same as that of chemical polishing, that is, to make the surface smooth by selectively dissolving the tiny protrusions on the surface of the material. Compared with chemical polishing, it can eliminate the influence of cathode reaction, and the effect is better. The electrochemical polishing process is divided into macro leveling and micro leveling.
4. Ultrasonic polishing: Put the workpiece into the abrasive suspension and place it in the ultrasonic field together, relying on the oscillation of the ultrasonic wave, 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 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, 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 waves in the liquid can also inhibit the corrosion process and facilitate surface brightening.
5. Fluid polishing: Fluid polishing relies on the high-speed flowing liquid and the abrasive particles it carries to scour the surface of the workpiece to achieve the purpose of polishing. Commonly used methods are: abrasive corundum jet processing, liquid jet processing, hydrodynamic grinding, etc. Hydrodynamic grinding is driven by hydraulic pressure, so that the liquid medium carrying abrasive particles flows back and forth across the surface of the workpiece at high speed. The medium is mainly made of special compounds with good flowability under relatively low pressure and mixed with abrasives. The abrasives can be silicon carbide powder of abrasives.
6. Magnetic grinding and polishing: Magnetic grinding and polishing is to use 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. With suitable abrasives, the surface roughness can reach Ra0.1m.
The polishing mentioned in plastic mold processing is very different from the surface polishing required in other industries. Strictly speaking, the polishing of abrasive tools with abrasives should be called mirror processing. It not only has high requirements on the polishing itself but also has high standards on surface flatness, smoothness and geometric accuracy. Surface polishing is generally only required to obtain a bright surface. The mirror processing of precision molds is still dominated by mechanical polishing.
