白小姐四肖必选一肖中特

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Status and New Development of Precision Machining Technology
Date: 2015-01-07 Popularity: 2241
Precision machining methods are becoming more and more important today. Precision machining technology has become the basis of the current high-tech field. Improving the precision of precision machining has become an urgent issue at present. At present, many scholars are doing a lot of research and experiments in this area, I believe that in the near future, precision machining technology will make great progress. I. Introduction to Precision Machining Technology At present, precision machining refers to machining technology with a machining accuracy of 1 ~ 0.1µm and a surface roughness of Ra0.1 ~ 0.01µm, but this limit is constantly changing with the advancement of machining technology. Today's precision Processing may be the normal processing of tomorrow. The problems to be solved in precision machining are: first, machining accuracy, including form and position tolerances, dimensional accuracy, and surface conditions; sometimes the presence or absence of surface defects is also the core of this problem; the second is machining efficiency. Some machining can achieve better machining accuracy. However, it is difficult to obtain high processing efficiency. Precision machining should include processing techniques such as microfabrication, ultra-microfabrication, and finishing. 2. Several commonly used precision machining methods and characteristics Traditional precision machining methods include cloth wheel polishing, abrasive belt grinding, ultra-fine cutting, fine grinding, honing, grinding, ultra-refined polishing technology, magnetic particle smoothing, etc. Abrasive belt grinding is the processing of workpieces by using a blended fabric with abrasives as the abrasive tool. It belongs to the category of coated abrasive tool grinding and has the characteristics of high productivity, good surface quality, and wide range of use. Foreign countries have made great achievements in belt materials and manufacturing processes. With belt series suitable for different occasions, general and special belt grinders have been produced, and the degree of automation has been continuously improved (already fully automatic and adaptive Controlled belt grinders), but there are few varieties of domestic belts, the quality needs to be improved, and the machine tools are still in the transformation stage. Precision cutting, also known as diamond tool cutting (SPDT), uses high-precision machine tools and single crystal diamond tools for cutting. It is mainly used for precision machining of soft metals such as copper and aluminum that are not suitable for grinding, such as magnetic drums for computers, Magnetic disks and metal reflectors for high-power lasers are 1-2 grades more accurate than general cutting processes. For example, the cylindricalness of the plunger hole of the rotor of a hydraulic motor processed by precision turning is 0.5 ~ 1µm, and the dimensional accuracy is 1 ~ 2µm; the surface roughness of the infrared reflector is Ra0.01 ~ 0.02µm, and it also has good optical properties. From a cost point of view, the cost of using precision-cut optical reflectors is about half or a fraction of that of the latter compared with products that were previously ground and processed with chrome plating. Honing heads composed of whetstone strips for honing, reciprocating along the surface of the workpiece under a certain pressure, and the surface roughness after processing can reach Ra0.4 ~ 0.1µm and Ra0.025µm. It is mainly used for processing cast iron and steel. It is not suitable. Used to process non-ferrous metals with low hardness and good toughness. Precision grinding and polishing is a machining method in which the abrasive and processing fluid, workpiece and grinding tool are mechanically rubbed between the workpiece and the tool to achieve the required size and accuracy. Precision grinding and polishing can achieve the accuracy and surface roughness that cannot be achieved by other processing methods for metal and non-metal workpieces. The roughness of the surface being polished Ra≤0.025µm. The processing deterioration layer is small, the surface quality is high, and the equipment is precision grinding Simple, mainly used for the processing of planes, cylindrical surfaces, gear tooth surfaces, and spouse parts with sealing requirements. It can also be used for the finishing of gauges, gauge blocks, injectors, valve bodies and spools. Polishing is a micro-processing of the surface of a workpiece by mechanical, chemical, and electrochemical methods. It is mainly used to reduce the surface roughness of workpieces. Common methods are: manual or mechanical polishing, ultrasonic polishing, chemical polishing, electrochemical polishing, and Electrochemical mechanical composite processing. Manual or mechanical polishing is the use of a polisher coated with abrasive paste, under a certain pressure, relative movement with the surface of the workpiece to achieve the finishing of the surface of the workpiece. After processing, the surface roughness of the workpiece Ra≤0.05μm, which can be used for polishing the plane, cylinder, curved surface and mold cavity. The effect of manual polishing is related to the skill of the operator. Ultrasonic polishing is the use of ultrasonic vibration on the end surface of the tool. The hard and brittle materials are smoothed by the abrasive suspension. The processing accuracy is 0.01 ~ 0.02μm and the surface roughness is Ra0.1μm. Ultrasonic polishing equipment is simple, easy to operate and maintain. Tools can be made of softer materials without complicated movements. It is mainly used to process hard and brittle materials, such as non-conductive non-metal materials. When processing conductive hard metal materials Time, productivity is low. Chemical polishing uses oxidants such as nitric acid and phosphoric acid to oxidize the surface of the processed metal under certain conditions to make the surface flat and shiny. Chemical polishing equipment is simple and can process various shapes of workpieces with high efficiency. The surface roughness of the processing is generally Ra≤0.2µm, but the corrosive fluid will damage the human body and equipment and pollute the environment, which needs to be handled properly. Mainly used for bright modification processing of stainless steel, copper, aluminum and its alloys. Third, the development trend of precision processing 1. Processing methods based on new principles Efforts are made to develop precision processing methods with extremely small processing units, and the error of the processing mechanism itself makes the error less than 1nm. At present, the processing methods with relatively small processing units mainly include elastic destruction processing, chemical processing, ion beam processing, electron beam processing, and plasma processing. From the perspective of the machining mechanism of current diamond cutting and diamond wheel precision grinding, the processing units are very large. 2. The development of precise mechanical mechanisms, whether machining or measuring devices, requires precise mechanical mechanisms, including guide rails, feed mechanisms and bearings. Ultra-precision air static pressure guide rails are currently the guide rails, and their straightness can reach (0.1 ~ 0.2) µm / 250mm, straightness can be further improved through compensation technology, but it is not as rigid as a hydrostatic guide. At the same time, since the thickness of the air film of the air static pressure guide rail is only about 10µm, pay attention to dust prevention during use. In addition, in the design of the guide rail, multiple rails can be connected in parallel to equalize the error of the gas film. Rolling guides made of highly elastic alloy and ruby have a system error of about 0.5µm, and random errors may exceed 0.1µm. 3. Develop a high-precision test system. In the current ultra-precision machining field, there are mainly two methods for measuring the machining accuracy; laser detection and grating detection, and the application of gratings. At present, the measurement accuracy of gratings can reach nm level. For example, the grating system of Beijing Photoelectric Instrument Research Center can reach 0.1µm, the holographic grating system in Russia can reach 10nm, the resolution of LG100 grating system can reach 0.1µm, and the measurement range is 100mm. The prerequisite for the development of detection instruments and control devices with small system errors, high accuracy and high reliability is the development of high-performance sensors and servo followers. If a high-performance sensor and servo mechanism and a high-precision, high-speed, and high-reliability reading device are developed, detection, analysis, and calculation can be performed by using a computer to improve detection accuracy. 4. Develop new materials that are suitable for precision machining and can obtain high precision and high surface quality. For example, recently developed ultra-fine powder sintered metals, amorphous metals, ultra-fine powder ceramics, amorphous semiconductor ceramics, and composite polymer materials. As long as development or breakthrough is achieved in one of the above aspects, it will inevitably lead to the rapid development of precision machining technology.
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