.1 Precision machining and ultra-precision machining The development of manufacturing technology has a history of thousands of years, from the stone age, the saw age, the iron age to the modern polymer plastic age; from hand-made, machine-made to modern intelligence Control automated production; at the same time, from general precision processing, precision processing to ultra-precision processing, it has now reached the widely spread nano-processing state, and is gradually approaching the limit of processing precision and surface quality, which represents an important aspect of current advanced manufacturing technology . Therefore, precision machining and ultra-precision machining represent precision machining
At different stages of development, due to the continuous development of manufacturing technology, the boundaries of the division will gradually move forward along with the historical process. The precision machining in the past is now a general machining, and the boundaries of the division are relative, and In specific precision number
There is no exact definition of value so far.
At present, precision machining refers to a machining technology with a machining accuracy of 1 to 0.1 and a surface roughness ^Ol-O.Olpn. Ultra-precision machining refers to a machining technology with a machining error of less than 0.1 mesh and a surface roughness less than RaO.a25pm. Also called sub-micron processing. However, ultra-precision machining has entered the nano-level at present, and is called nano-machining and corresponding nano-technology. From the perspective of precision machining and ultra-precision machining, it should include processing technologies such as micro-machining and ultra-fine machining, smoothing and finishing.
Micro-machining and ultra-micro-processing technology refer to the processing technology for manufacturing small-size parts. They are proposed for the manufacturing requirements of integrated circuits. Due to the small size, the accuracy is expressed by the size of the shoulder, rather than the general size In that way, it is expressed by the value of the processed size and the size error. Finishing processing technology generally refers to a processing method that reduces the surface roughness value and improves the mechanical and mechanical properties of the surface layer, and does not emphasize the improvement of the processing degree. In recent years, the corresponding finishing concept has been put forward, emphasizing the two aspects of precision and surface quality. However, in terms of the concept of finishing and finishing, there are aspects of rough finishing.
1.2 Features of precision machining and ultra-precision machining
Precision machining and ultra-precision machining are under development, and currently have the following characteristics.
(1) The formation of systematic engineering precision machining and ultra-precision machining is a multi-disciplinary comprehensive advanced technology. To achieve high precision and high surface quality, not only the processing method itself, but also the processed materials, processing equipment and process equipment must be considered. , Testing methods, working environment and human skill level, etc. Therefore, the isolated processing method cannot achieve the predetermined effect, and must be supported by comprehensive technology and conditions, thus forming a precision processing system. The combination of precision machining technology and system theory, methodology, computer technology, information technology, transmitter technology, and digital control technology has further contributed to the formation of precision machining systems engineering. While studying the theory of precision machining and warping precision machining, surface forming mechanism, and establishing mathematical models, various related technologies should also be studied.
(2) Precision machining and ultra-precision machining are closely related to micro-machining and ultra-fine machining. Micro-machining and ultra-fine machining refer to the production and processing technology of manufacturing micro-sized parts and ultra-micro-sized parts. The emergence and development of microfabrication and ultra-microfabrication are closely related to integrated circuits. Integrated circuits require more components to be fabricated on a small area of
Micro machining and general size machining are different in concept and mechanism. In general size machining, the accuracy is expressed in tolerance units, tolerance = tolerance grade factor x tolerance unit, the same precision has the same tolerance grade factor, but the tolerance unit Depending on the size of the basic size, the larger the basic size, the larger the tolerance unit, and there are different formulas for calculating the range of the basic size. In the case of micro processing, since the processing size is small, the accuracy is expressed by the absolute value of the size. Because from the perspective of the workpiece, the biggest difference between general machining and micro machining is the size (thickness) of the chips. The amount of back-grabbing is extremely small during micro-machining, and the cutting is performed inside the crystal of the material. The amount of cutting removal is expressed by “processing unit size” or “processing unit”. The size of “processing unit” represents the level of machining accuracy, such as Molecular level processing, atomic level processing.
Although micro-machining and general-size processing are different in concept and mechanism, from the point of view of processing technology, micro-processing is mainly processing small sizes, while precision processing and ultra-precision processing both process large sizes and small sizes. Therefore, Micro-machining belongs to the category of precision machining and ultra-precision machining. In fact, many of the processing methods of the two are the same, but the processing objects are different.
(3) Precision machining and ultra-precision machining are closely related to special machining. Special machining refers to non-traditional machining square waves that use energy such as machinery, light, electricity, sound, heat, chemistry, magnetism, and atoms. It is fast, not only can adopt a single processing method, but also a compound processing method, which is widely used. At present, many precision processing and ultra-precision processing methods have adopted special processing techniques such as laser processing and ion beam processing, opening up new ways of precision processing and ultra-precision processing,-some high-hardness, brittle and difficult-to-process materials, such as hardened steel , Cemented carbide, mesh porcelain, quartz, diamond, etc., some parts with poor rigidity and easy to deform during processing, such as thin-walled parts, Zen parts, etc., special processing is already necessary for precision processing and ultra-precision processing. , Even the only means to form precision special processing. At present, although traditional processing methods still occupy a large proportion and are the main processing methods, they should be emphasized and further developed. However, due to the rapid rise of special processing, not only many new processing mechanisms have emerged, but also various composite processing technologies have emerged. Combining several processing methods to play their respective strengths and complement each other has great potential to improve processing accuracy, surface quality and efficiency, and expand the scope of processing applications.
(4) Integration of processing and testing. The processing accuracy and surface quality of precision processing and super-finish coil processing are both high. Therefore, there must be corresponding testing methods to show whether the technical requirements are met. Therefore, in precision machining and precision machining, both machining and inspection are difficult, and the inspection is often more difficult. Only the strategy of integrating processing and inspection is adopted, and inspection is considered at the same time of processing.
From the time domain analysis of the detection process, detection can be divided into three categories: high-line detection, in-position detection and online detection. Offline inspection refers to the inspection in the inspection room after processing is completed. Therefore, processing and inspection are separated. If the inspection fails, it is generally difficult to repair due to the high processing accuracy. In-place inspection means that after the processing is completed, the workpiece is not unloaded and inspected on the machine tool. If the inspection fails, it can be repaired in time. There will be no errors caused by re-fixing during repair, but offline inspection and in-position must be considered Detect the impact of the difference in the testing environment on the test results. On-line inspection is to conduct real-time inspection during the processing, grasp the processing error value and its development trend at any time, and carry out real-time control, which is a dynamic inspection process. Error compensation is an effective technical measure to improve machining accuracy, which can be divided into two categories: static error compensation and dynamic error compensation. Static error compensation is mainly used to compensate the system error in the process system, such as error correction ruler. Dynamic error compensation is real-time compensation during processing, which can compensate for random errors and system errors in the process system. Dynamic error compensation and online detection are closely related.
The development of numerical control technology, computer control technology, rattan transmitter technology, and micro-displacement mechanism has enriched the error compensation methods, especially the online detection and dynamic error compensation have made great progress. In precision machining and ultra-precision machining, inspection and error compensation are important measures for the integration of machining and inspection.
(5) Precision machining and ultra-precision machining are closely related to automation technology. Manufacturing automation is an important part of advanced manufacturing technology. Its role is not only to improve efficiency, increase labor productivity, improve working environment and labor conditions, but also improve processing accuracy. It is an important measure to improve surface quality, avoid human error caused by manual operation, and ensure processing quality and its stability. At the same time, it is a powerful measure to quickly respond to market demand and shorten the manufacturing cycle. To achieve high-quality precision machining and ultra-precision machining, it must rely on automation technology to ensure. Technologies such as process optimization and adaptive control, detection and error compensation, and computer control are all automation technologies that improve and ensure processing quality. Although the processing quality of precision processing and ultra-precision processing is still guaranteed by the skills of workers, processing methods such as grinding and scraping still rely on handwork, but from the perspective of development trends, the proportion of automation technology that replaces handwork is increasing. The processing effect is getting better and better.
(6) The development of precision machining and ultra-precision machining is closely related to product demand. Precision machining and ultra-precision machining require high processing quality, are technically difficult, involve a wide range of areas, and have many influencing factors. Therefore, investment is often large. Therefore, the development of precision machining and ultra-precision machining is closely related to specific product requirements. For example, the Lawience Live-mor Laboratory of the University of California and the Y-12X Factory jointly developed the DTM-3 model in 1989 with the support of the Ministry of Energy. Ultra-precision diamond lathes are aimed at processing various mirrors for laser fusion, antennas for large astronomical telescopes, etc., reflecting the needs of aerospace technology. The development of precision machining and ultra-precision machining technology in our country is also carried out in conjunction with the specific needs of aerospace and aviation technology. At present, the standardization and serialization of precision machine tools and ultra-precision machine tools is far less than that of ordinary machine tools, and there are not enough varieties. The main reason is that the technology is not promoted enough, the versatility is not strong, and the price is very expensive. With the expansion of market demand, With the improvement of product quality and the continuous maturity of precision processing technology, generalized and serialized precision processing and ultra-precision processing equipment will certainly be more widely used in production practice.