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2018-08
Popularize the commonly used plane grinding and polishing methods
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At present, the commonly used plane grinding and polishing methods are as follows:
1. Mechanical polishing Mechanical polishing is a polishing method to obtain a smooth surface by removing the polished convex part by cutting and plastic deformation of the material surface. Generally, oilstone strips, wool wheels, abrasive paper, etc. are used, mainly by manual operation. For special parts such as the surface of the swivel body, auxiliary tools such as turntable can be used. For those with high surface quality requirements, the ultra-precision polishing method can be used. The ultra-precision polishing method uses special abrasive tools. In the polishing fluid containing abrasive, Press tightly on the machined surface of the workpiece for high-speed rotation. Ra0.008 can be achieved by using this technology μ The surface roughness of m is the highest among various polishing methods. This method is often used for optical lens moulds.
2. Chemical polishing Chemical polishing is to dissolve the concave part of the surface micro-protruding part of the material in the chemical medium, so as to obtain a smooth surface. The main advantage of this method is that it does not need complex equipment, and 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 polishing solution. The surface roughness obtained by chemical polishing is generally 10 μ m。
3. 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 protruding part of the material surface. Compared with chemical polishing, it can eliminate the influence of cathodic reaction and has better effect.
The electrochemical polishing process is divided into two steps:
(1) The macro-leveling solution product diffuses into the electrolyte, and the geometric roughness of the material surface decreases, Ra>1 μ m。
(2) Low light level flat anodic polarization, surface brightness increased, Ra<1 μ m。
4. Ultrasonic polishing places the workpiece in the abrasive suspension and put it in the ultrasonic field together, and makes the abrasive grind and polish on the workpiece surface by relying on the oscillation of the ultrasonic wave. Ultrasonic machining has small macro force and will 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, ultrasonic vibration is applied to stir the solution to separate the dissolved products on the surface of the workpiece, and the corrosion or electrolyte near the surface is uniform; The cavitation effect of ultrasonic wave in the liquid can also inhibit the corrosion process and facilitate the surface brightness.
5. Fluid polishing Fluid polishing is to achieve the purpose of polishing by scouring the workpiece surface with high-speed flowing liquid and abrasive particles. Common methods include abrasive jet machining, liquid jet machining, hydrodynamic grinding, etc. Hydrodynamic grinding is driven by pneumatic data ">hydraulic pressure, so that the liquid medium carrying abrasive particles flows through the workpiece surface at high speed. The medium is mainly made of special compounds (polymeric substances) with good flowability under low pressure and mixed with abrasive, and the abrasive can be silicon carbide powder.
6. Magnetic abrasive polishing Magnetic abrasive polishing uses magnetic abrasive to form abrasive brush under the action of magnetic field to grind the workpiece. This method has high processing efficiency, good quality, easy control of processing conditions and good working conditions. With proper abrasive, the surface roughness can reach Ra0.1 μ m。
2、 Basic methods of mechanical polishing
The polishing in plastic mold processing is very different from the surface polishing required in other industries. Strictly speaking, mold polishing 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 only a bright 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 electrolytic polishing, fluid polishing and other methods are difficult to accurately control the geometric accuracy of parts, and the surface quality of chemical polishing, ultrasonic polishing, magnetic abrasive polishing and other methods can not meet the requirements, so the mirror processing of precision molds is still based on mechanical polishing.
2.1 The basic procedure of mechanical polishing is to obtain high-quality polishing effect. It is important to have high-quality polishing tools and accessories such as oilstone, abrasive paper and diamond grinding paste. The selection of polishing procedure depends on the surface condition after preliminary processing, such as machining, EDM, grinding, etc
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