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Polishing method of plastic mold

Update:29-11-2019
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Mechanical polishing Mechanical polishing is a polishin […]

Mechanical polishing
Mechanical polishing is a polishing method that obtains a smooth surface by cutting and plastic deformation of the surface of the material to remove the polished protrusions. Generally, you use whetstone strips, wool wheels, sandpaper, etc., mainly manual operations. Using auxiliary tools such as turntables, super-refined polishing can be used for high surface quality requirements. The ultra-precise grinding polishing adopts a special grinding tool. In the grinding polishing liquid containing abrasives, it is pressed against the surface of the workpiece to be processed for high-speed rotation. Using this technology can achieve a surface roughness of Ra0.008μm, which is the highest among various polishing methods. This method is often used in optical lens molds.
Chemical polishing
Chemical polishing is to make the surface of the material microscopically convex in the chemical medium dissolve preferentially, 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 liquid. The surface roughness obtained by chemical polishing is generally several tens of μm.
Electrolytic polishing
The basic principle of electrolytic polishing is the same as chemical polishing, that is, the surface is smooth by selectively dissolving the tiny protrusions 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: ⑴ Macro leveling The dissolved product diffuses into the electrolyte, and the surface roughness of the material decreases, Ra> 1μm. ⑵Low light leveling Anodized, surface brightness improved, Ra <1μm. Ultrasonic polishing The workpiece is placed in the abrasive suspension and placed in an ultrasonic field together, and the abrasive is ground and polished on the surface of the workpiece by the ultrasonic vibration. Ultrasonic machining has a small macro force and does not cause deformation of the workpiece, but the production and installation of the 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 dissolve the dissolved products on the surface of the workpiece, and the corrosion or electrolyte near the surface is uniform; the cavitation of ultrasonic waves in the liquid can also suppress the corrosion process and facilitate the surface brightening. Fluid polishing Fluid polishing relies on high-speed flowing liquid and abrasive particles carried by it to wash the surface of the workpiece to achieve the purpose of polishing. Common methods are: abrasive 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 workpiece surface at high speed. The medium is mainly made of special compounds (polymer-like substances) that flow through under low pressure and mixed with abrasives. The abrasives can be silicon carbide powder. Magnetic grinding and polishing Magnetic abrasive polishing is the use of magnetic abrasives to form abrasive brushes under the action of a magnetic field to grind workpieces. This method has high processing efficiency, good quality, easy control of processing conditions, and good working conditions. With a suitable abrasive, the surface roughness can reach Ra0.1μm. 2 Mechanical polishing based on this method The polishing in plastic mold processing is very different from the surface polishing required in other industries. Strictly speaking, the polishing of the mold should be called mirror processing. It not only has high requirements for polishing itself, but also has high standards for surface flatness, smoothness and geometric accuracy. Surface polishing generally requires only a shiny surface. The standard of mirror processing is divided into four levels: AO = Ra0.008μm, A1 = Ra0.016μm, A3 = Ra0.032μm, A4 = Ra0.063μm. It is difficult to precisely control the geometric accuracy of the part due to methods such as electrolytic polishing and fluid polishing. However, the surface quality of chemical polishing, ultrasonic polishing, magnetic abrasive polishing and other methods can not meet the requirements, so the mirror surface processing of precision molds is mainly mechanical polishing.

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