The main purpose of polishing the mold is two, one is to increase the brightness of plastic mold, beautiful. Two is to make mold easily demoulding. At the time of polishing generally using coarse aggregate on the surface of mould cavity machining for coarse grinding, knife grinding to machine tool, and then use the fine aggregate to coarse grinding stone to trace, and then use the surface fine sandpaper to fine stone polished into grinding, then use polishing paste or paste the cavity surface of the die for the final polishing grinding, finally achieve the effect of bright as a mirror. In daily life, our common plastic mold has six polishing methods:
1. Mechanical polishing
Mechanical polishing by cutting, surface plastic deformation was removed after polishing and convex smooth surface polishing method, the general use of oilstone, wool wheel, sand paper, mainly manual, special parts such as rotary table surface, can use auxiliary tools such as high surface quality requirements can be used method ultra precision polishing. Ultra precision polishing is made of special abrasive tools, which are tightly pressed on the machined surface of the workpiece in the polishing fluid containing abrasives, so as to rotate at high speed. Using this technique, the surface roughness of Ra0.008 micron M can be reached, which is the highest in various polishing methods. This method is often used in optical lens moulds.
2. Chemical polishing
Chemical polishing is to make the material in the chemical medium surface micro protruding part of the concave part of the first dissolved, so as to obtain smooth surface. The main advantage of this method is that the complex workpiece can be polished without complex equipment, and many workpieces can be polished at the same time, and the efficiency is high. The key problem of chemical polishing is the preparation of polishing fluid. The surface roughness obtained by chemical polishing is generally 10 m.
Electrolytic polishing is basically the same as chemical polishing, that is, by selectively dissolving the tiny protrusion of the surface of the material to smooth the surface. Compared with chemical polishing, the effect of cathodic reaction can be eliminated, and the effect is better. The electrochemical polishing process is divided into two steps:
(1) macro leveling dissolved products diffused into the electrolyte, and the surface roughness of the material decreased, Ra>1, M.
(2) polarization of the micro smooth anode, and the brightness of the surface is increased by Ra<1 M.
4. Ultrasonic polishing
The workpiece is placed in the abrasive suspension and placed in the ultrasonic field together, and the abrasive is polished on the workpiece surface by the oscillating action of the ultrasonic wave. Ultrasonic machining has small macro force and can not cause workpiece deformation, but it is difficult to make and install tooling. Ultrasonic machining can be combined with chemical or electrochemical methods. On the basis of solution corrosion and electrolysis, the ultrasonic vibration stirring solution is applied to make the dissolution product of the workpiece separate from the surface, and the corrosion or electrolyte is uniform near the surface. The cavitation effect of ultrasonic wave in liquid can also inhibit the corrosion process, which is beneficial to the surface lighting.
5. Fluid throwing
Fluid polishing is based on high speed flow of liquid and its abrasive particles to scour the surface of the workpiece to achieve polishing purposes. Commonly used methods are: abrasive jet machining, liquid jet machining, fluid dynamic grinding, etc.. Fluid dynamic grinding is driven by hydraulic pressure, which makes the liquid medium carrying abrasive particles flow back and forth to the surface of the workpiece at high speed. The medium is mainly made of special compound (polymer material) which is flowing through the lower pressure and mixed with abrasive. The silicon carbide powder can be used in the abrasive.
6. Magnetic abrasive finishing
Magnetic abrasive finishing is a kind of abrasive brush made of magnetic abrasive under the action of magnetic field, which is used to grind the workpiece. This method has the advantages of high processing efficiency, good quality, easy control of processing conditions and good working conditions. With proper abrasive, the surface roughness can reach Ra0.1 M.