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Author: MULAN –Plastic Molding Manufacturer
Plastic mold polishing, currently commonly used polishing methods are as follows: 1.1 Mechanical polishing: Mechanical polishing is a polishing method that removes the polished convex part by cutting and plastic deformation of the material surface to obtain a smooth surface. Generally, oil stone strips, wool Wheels, sandpaper, etc. are mainly operated by hand. For special parts such as the surface of the rotary body, auxiliary tools such as turntables can be used. For high surface quality requirements, the method of ultra-fine grinding and polishing can be used. Ultra-fine polishing uses a special abrasive tool, which is pressed against the surface of the workpiece to be processed in a polishing liquid containing abrasives for high-speed rotation. 1.2 Chemical polishing Chemical polishing is to make the microscopic protruding part of the surface of the material dissolve preferentially compared with the concave part in the chemical medium, 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. 1.3 Electrolytic polishing The basic principle of electrolytic polishing is the same as that of chemical polishing, that is, to make the surface smooth by selectively dissolving the tiny protrusions on the surface of the material. Compared with chemical polishing, it can eliminate the influence of cathode reaction, and the effect is better.
1.4 Ultrasonic polishing The workpiece is put into the abrasive suspension and placed together in the ultrasonic field, relying on the oscillation of the ultrasonic wave, the abrasive is ground and polished on the surface of the workpiece. Ultrasonic machining has a small macroscopic force and will not cause deformation of the workpiece, but it is difficult to manufacture and install tooling. Ultrasonic machining can be combined with chemical or electrochemical methods.
On the basis of solution corrosion and electrolysis, ultrasonic vibration is applied to stir the solution, so that the dissolved products on the surface of the workpiece are separated, 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 surface brightening. 1.5 Fluid polishing Fluid polishing relies on the high-speed flowing liquid and the abrasive particles it carries to scour the surface of the workpiece to achieve the purpose of polishing. Commonly used 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 surface of the workpiece at high speed. The medium is mainly made of a special compound (generally a polymer-like substance) with good flowability under low pressure and mixed with abrasives. The abrasives can be silicon carbide powder. 1.6 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 the workpiece.
This method has high processing efficiency, good quality, easy control of processing conditions, and good working conditions. 2 Basic methods of mechanical polishing The polishing mentioned in plastic mold processing is very different from the surface polishing required in other industries. To be precise, the polishing of molds 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 obtaining a bright surface. 2.1 Basic procedure of mechanical polishing To obtain a high-quality polishing effect, the most important thing is to have high-quality polishing tools and accessories such as oilstone, sandpaper and diamond abrasive paste. The choice of polishing procedure depends on the surface condition after pre-processing, such as machining, EDM, grinding and so on.
The general process of mechanical polishing is as follows: (1) Coarse polishing The surface after milling, EDM, grinding and other processes can be polished in a rotating surface polishing machine or an ultrasonic grinding machine at a selectable speed. After that, it is manually grinded with oilstone, and the strip-shaped oilstone is added with kerosene as a lubricant or coolant. (2) Semi-fine polishing Semi-fine polishing mainly uses sandpaper and kerosene.
(3) Fine polishing Fine polishing mainly uses diamond abrasive paste.