With the increasingly wide application of plastic products, such as daily chemical products and beverage packaging containers, the needs of appearance often require the surface of the plastic mold cavity to reach the degree of mirror polishing. The requirements for surface roughness are high, so the requirements for polishability are also high.
Plastic mold polishing not only increases the beauty of the workpiece, but also improves the corrosion resistance and wear resistance of the material surface, and can also make the mold have other advantages, such as making the plastic products easy to demould, reducing the production injection cycle, etc. Therefore, polishing is used in plastic molds. It is a very important process in the manufacturing process. The commonly used polishing methods are as follows.
Mechanical polishing is a polishing method in which a smooth surface is obtained by cutting and plastic deformation of the surface of the material to remove the polished convex part. Generally, whetstone strips, wool wheels, sandpaper, etc. are used. Using auxiliary tools such as turntables, ultra-fine grinding and polishing methods can be used for those with high surface quality requirements. Ultra-fine grinding and polishing is to use a special grinding tool, in the grinding and polishing liquid containing abrasive, it is pressed tightly on the machined surface of the plastic table mold workpiece, and it rotates at a high speed. The use of this technology is relatively high among various polishing methods.
Chemical polishing is to allow the microscopically protruding parts of the material to dissolve preferentially over the concave parts in the chemical medium, thereby obtaining 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 task pieces at the same time, with high efficiency. The core problem of chemical polishing is the preparation of polishing liquid.
The basic principle of electrolytic polishing is the same as that of chemical polishing, that is, the small protrusions on the surface of the material are selectively dissolved to make the surface smooth. Compared with chemical polishing, the effect is better. The electrochemical polishing process of plastic table mold is divided into two steps:
(1) Macro leveling. The dissolved products diffuse into the electrolyte, and the surface roughness of the material decreases.
(2) The shimmer is smooth. Anodized, the surface brightness is improved.
(3) Fluid polishing. Fluid polishing relies on high-speed flowing liquid and the abrasive particles carried by it to scour the surface of the workpiece to achieve the purpose of polishing. Commonly used methods are: abrasive jet machining, liquid jet machining, hydrodynamic grinding, etc. Hydrodynamic grinding is driven by hydraulic pressure, so that the liquid medium carrying abrasive particles flows reciprocatingly across the surface of the workpiece at high speed. The medium is mainly made of special compounds (polymer-like substances) with good performance at low pressure and mixed with abrasives, and the abrasives can be silicon carbide powder.
(4) 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 plastic table mold workpieces. This method has high processing efficiency, good quality, easy control of processing conditions and good working conditions. Use suitable abrasives.