1 mechanical polishing
The advantage is that the finished parts have good leveling and high brightness. The defects are labor intensity, severe pollution, and complicated parts can not be processed, and the gloss can not be consistent, the gloss maintenance time is not long, boring and rusting. Contrast suitable for processing simple parts, medium and small products.
Mechanical polishing is a polishing method that removes the polished convex portion by plastic deformation of the material surface, and generally uses a stone strip, a wool wheel, a sandpaper, etc., and is mainly operated by hand, and special parts such as a rotary external surface can be used. Using auxiliary tools such as turntables, the quality of the exterior is high, and the method of super-finishing can be adopted. Ultra-fine grinding is a special-purpose grinding tool. In the polishing liquid containing abrasive, it is pressed against the surface of the workpiece to be processed for high-speed rotation. With this technology, the appearance of Ra0.008μm can be reached, which is the highest among various polishing methods. Optical lens molds are often used this way.
2 chemical polishing
Its strength is that the investment in processing equipment is small, the parts can be thrown, the speed is fast, the efficiency is high, and the corrosion resistance is good. The defect is that the brightness is poor, there is gas overflow, ventilation equipment is needed, and heating is difficult. It is suitable for processing small batches of bulky parts and products with low brightness requirements for small parts.
Chemical polishing is to make the material in the chemical medium, the macroscopically convex part of the material is preferentially dissolved, so that a smooth surface is obtained. The important advantage of this method is that it does not require complicated equipment, can polish a complex workpiece, 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.
Its strength is that the gloss of the mirror is long, the process is stable, the pollution is low, the cost is low, and the corrosion resistance is good. The defects are high anti-pollution, large-time investment in processing equipment, complicated tools, auxiliary electrodes, and large-scale production of cooling equipment. Suitable for mass production, important for advanced products, export products, and tolerance products, the processing technology is stable, and the operation is relatively simple.
The principle of electropolishing roots is the same as that of chemical polishing, that is, by selectively dissolving the outer surface of the material to make the surface smooth. Compared with chemical polishing, the effect of the cathode reflection can be removed, and the effect is better.
The electrochemical polishing process is divided into two steps:
(1) Macro leveling The dissolved product is dispersed in the electrolyte, and the geometric appearance of the material is reduced, Ra>1 μm.
(2) Low-light flat anodic polarization, the appearance brightness is improved, Ra<1μm.
4 ultrasonic polishing
The workpiece is placed in the abrasive suspension and placed together in the ultrasonic field, relying on the ultrasonic vibration to make the abrasive surface grinding and polishing on the workpiece. Ultrasonic machining has a small macroscopic force and does not cause deformation of the workpiece, but the tooling is difficult to manufacture and install.
Ultrasonic processing can be combined with chemical or electrochemical means. On the root of solution corrosion and electrolysis, ultrasonic vibration stirring solution is applied to dissociate the dissolved products on the surface of the workpiece, and the corrosion or electrolyte average on the left side of the workpiece; the cavitation of the ultrasonic wave in the liquid can also suppress the corrosion process, which is conducive to the appearance of light.
5 fluid polishing
Fluid polishing relies on high-speed flow of liquid and the abrasive particles it carries to flush the surface of the workpiece to the target of polishing. Commonly used methods are: abrasive radiation processing, liquid radiation processing, fluid dynamic grinding, and the like. The hydrodynamic grinding is driven by hydraulic pressure to allow the liquid medium carrying the abrasive particles to flow back and forth through the workpiece at high speed.
The medium is preferably made of a special compound (polymeric substance) which flows at a lower 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 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.
At present, the most important polishing methods for parts made by MIM process are magnetic grinding and mechanical polishing.
The polishing described in plastic mold processing is very different from the surface polishing required in other industries. Many polishing of the mold can be called mirror processing. Not only does it have high requirements for polishing itself, but it also has a high standard for surface flatness, smoothness and geometric accuracy.
Surface polishing generally requires only a shiny surface.
The standard for mirror processing is divided into four levels: AO=Ra0.008 μ m , A1=Ra0.016 μ m , A3=Ra0.032 μ m , A4=Ra0.063 μ m. Because electropolishing, fluid polishing and other methods are difficult to precisely control the geometric accuracy of the part, and the surface quality of chemical polishing, ultrasonic polishing, magnetic polishing and other methods can not meet the requirements, so the mirror processing of precision mold is still mechanical polishing the Lord.