There are two main purposes for polishing the mould. One is to increase the brightness of the plastic mould and make it beautiful. The second is to make the mould easy to demould. In the polishing process, the surface of the machined mould cavity is generally roughened with coarse oil stone, and the tool marks of the machine and the tool are polished, and then the fine oil stone is used to polish the rough stone to reach the trace, and then the fine Sandpaper polishes the polished surface of the fine stone, and then uses the polishing paste or abrasive paste to finish the surface of the cavity of the mould by * polishing to achieve a bright, mirror-like effect.
In daily life, our common plastic moulds have six polishing methods:
1.mechanical polishing
Mechanical polishing is a polishing method that removes the polished convex portion by plastic deformation on the surface of the material to obtain a smooth surface. Generally, oil stone strips, wool wheels, sandpaper, etc. are used, which are mainly manual operations, and special parts such as the surface of the rotating body can be used. Using an auxiliary tool such as a turntable, the method of super-fine polishing can be used with high surface quality requirements. Ultra-fine grinding and polishing is a special-purpose grinding tool. In the polishing liquid containing abrasive, it is pressed against the machined surface to perform high-speed rotary motion. With this technology, a surface roughness of Ra0.008 μm can be achieved, which is among various polishing methods. This method is often used in optical lens moulds.
2.chemical polishing
Chemical polishing is a process in which a portion of a material that is microscopically convex in a chemical medium is preferentially dissolved in a concave portion to obtain a smooth surface. The main advantage of this method is that it can polish a workpiece with complex shapes without complicated equipment, and can polish many workpieces at the same time with high efficiency. The core issue of chemical polishing is the formulation of the polishing fluid. The surface roughness obtained by chemical polishing is generally several 10 μm.
3.electrolytic polishing
Electropolishing is basically the same as chemical polishing, which is to selectively dissolve the surface of the material to make the surface smooth. Compared with chemical polishing, the effect of the cathode reaction can be eliminated, and the effect is good. The electrochemical polishing process is divided into two steps:
(1) Macroscopically leveling the dissolved product to diffuse into the electrolyte, and the surface roughness of the material is reduced, Ra>1 μm.
(2) Low-light leveling anodic polarization, surface brightness is improved, Ra<1μm.
4.ultrasonic polishing
The workpiece is placed in an abrasive suspension and placed together in an ultrasonic field, and the abrasive is ground and polished on the surface of the workpiece by the action of ultrasonic waves. Ultrasonic machining has a small macroscopic force and does not cause deformation of the workpiece, but it is difficult to manufacture and install the tooling. Ultrasonic processing can be combined with chemical or electrochemical methods. On the basis of solution corrosion and electrolysis, the ultrasonic vibration stirring solution is applied to dissociate the dissolved products on the surface of the workpiece, and the corrosion or electrolyte near the surface is uniform; the cavitation of the ultrasonic wave in the liquid can also inhibit the corrosion process, which is favorable for surface illuminating.
5.fluid toss
Fluid polishing relies on high-speed flowing liquids and abrasive particles carried by them to wash the surface of the workpiece for polishing purposes. Common methods are: abrasive jet processing, liquid jet processing, hydrodynamic grinding, and the like. The hydrodynamic grinding is hydraulically driven to cause the liquid medium carrying the abrasive particles to flow back and forth across the surface of the workpiece at high speed. The medium is mainly made of a special compound (polymeric substance) which flows at a relatively low pressure and is doped with an abrasive, and the abrasive can be made of silicon carbide powder.
6.magnetic grinding and polishing
Magnetic grinding and polishing is the use of a magnetic abrasive to form an abrasive brush 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 a suitable abrasive, the surface roughness can reach Ra 0.1 μm.