There are two main purposes for polishing the mold. One is to increase the brightness and aesthetics of the plastic mold. The second is to make the mold easy to release. In the process of polishing, the rough surface of the cavity of the machined mold cavity is roughly roughened with a rough oilstone, and the tool marks are ground to add a tool, and then the fine oilstone is polished with a fine whetstone to reach the mark, and then the fine mark is used. Sandpaper polishes the polished surface of the fine whetstone, and finally polishes the cavity surface of the mold with a polishing paste or a polishing paste, and finally achieves a bright, mirror-like effect. In daily life, our common plastic mold has six polishing methods:
1, mechanical polishing
Mechanical polishing is a polishing method in which a smooth surface is obtained by removing a convex portion after being polished by plastic deformation of a cutting surface or a material surface. Generally, an oil stone bar, a wool wheel, and a sandpaper are used, and the manual operation is mainly used. Special parts such as the surface of a rotating body can be used. Using an auxiliary tool such as a turntable, a high-precision surface polishing method can be used. Ultra-precision polishing is the use of special grinding tools, in the grinding liquid containing abrasive, pressed on the workpiece surface is processed for high-speed rotary motion. The use of this technology can achieve a surface roughness of Ra0.008 μm, which is the highest among various polishing methods. Optical lens molds often use this method.
2, chemical polishing Chemical polishing preferentially dissolves the relatively concave portions of the material microscopically protruding from the surface of the chemical medium, thereby obtaining a smooth surface. The main advantage of this method is that it does not require complicated equipment, it 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 a polishing liquid. The surface roughness obtained by chemical polishing is generally 10 μm.
3, electrolytic polishing Electropolishing is basically the same as chemical polishing, that is, by selectively dissolving tiny protruding portions of 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 two steps: (1) The macro-leveling of the dissolved products diffuses into the electrolyte, and the surface of the material is rough and rough, Ra>1 μm. (2) Low-level anodic polarization with low light level, Ra<1μm.
4, ultrasonic polishing The workpiece is placed in an 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 low macroscopic force and does not cause deformation of the workpiece, but tooling is difficult to manufacture and install. Ultrasonic processing can be combined with chemical or electrochemical methods. On the basis of solution corrosion and electrolysis, ultrasonic vibrating agitation solution is applied to remove the dissolved products on the surface of the workpiece 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 the surface brightening.
5, fluid toss Fluid polishing relies on the high-speed flow of liquid and the abrasive particles it carries to flush the surface of the workpiece for polishing purposes. Common methods are: abrasive jet machining, liquid jet machining, fluid power grinding and so on. Hydrodynamic grinding is driven by hydraulic pressure so that the liquid medium carrying the abrasive particles reciprocates across the surface of the workpiece at high speed. The medium is mainly made of a special compound (polymer-like material) that flows at a relatively low pressure and is made of an abrasive material. Silicon carbide powder may be used as the abrasive.
6, magnetic grinding and polishing Magnetic abrasive polishing is the use of magnetic abrasives to form abrasive brushes under the action of a magnetic field, grinding workpieces. 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 Ra 0.1 μm.