Current situation and development of the most effi

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The current situation and development of efficient flexible manufacturing technology in the 21st century, China's machine tool manufacturing industry is facing not only the good opportunity for the development of manufacturing equipment caused by the demand to improve the level of machinery manufacturing industry, but also the pressure of fierce market competition after China's entry into WTO. In terms of technology, accelerating the efficient flexible manufacturing technology with numerical control technology as the core will be the key to solve the sustainable development of machine tool manufacturing industry

CNC machine tools and manufacturing systems composed of CNC machine tools are important basic equipment for transforming traditional industries and building digital enterprises. Its development has been paid close attention to. Numerical control machine tool attracts people's attention with its excellent flexible automation performance, excellent and stable precision, agility and diversified functions, creating a precedent for the development of mechanical products to mechatronics. Therefore, numerical control technology has become one of the core technologies in advanced manufacturing technology. On the other hand, through continuous research, the deepening application of information technology has promoted the further improvement of CNC machine tools. Therefore, this paper will focus on analyzing the current situation and trend of numerical control technology, and discuss the role of efficient flexible manufacturing technology in promoting the development of machine tool manufacturing industry

basic evaluation indicators of CNC machine tools

cost, quality, productivity and output, and delivery date are the four elements to measure the production capacity and market competitiveness of enterprises. Only mass production that reaches a certain threshold can achieve the unification of the above four aspects by adopting the traditional non CNC production mode. However, in the current fierce market competition environment, the seller's market with production as the center and enterprise as the leading factor has turned to the buyer's market with market demand as the center and user as the leading factor. Product demand is diversified and personalized, and the economic life of products is greatly shortened. This will first form a production environment with multi variety and batch production as the mainstream; Secondly, the first factor to measure the competitiveness of enterprises has also changed from cost to delivery time

therefore, the development of CNC manufacturing technology equipment and manufacturing system with flexible structure system is the key to realize flexible and rapid response to user driven market demand in a rapidly changing market environment. The so-called flexibility of manufacturing equipment and manufacturing system means that when the variety demand of products changes, they can still realize the adaptability of timely conversion production on the premise of meeting the economy. At the same time, continuously improving the economic processing accuracy is also another major goal to adapt to the market competition. As the basic index to evaluate the efficiency of CNC machine tools and systems, the traditional working accuracy and cutting ability will be changed to the degree of high efficiency, flexibility and precision

high efficiency and flexibility

although the traditional non NC machine tool also has certain flexibility, it can not obtain high efficiency and stable accuracy, and it is not suitable for the processing of complex surfaces. Therefore, the high-efficiency flexible manufacturing equipment and its manufacturing system based on numerical control technology need to have the following characteristics:

* high flexibility and the use of this new type of plastic produced in multiple varieties. One of the methods is to use it to permanently bond the cylindrical battery with the surrounding battery cell support for rapid adaptability

* efficient production capacity, including: high productivity - by means of high speed and improving metal removal rate; High stability - for CNC machine tools with optical electromechanical integration, it is required to reduce the failure rate and improve the reliability, so as to improve the starting rate (utilization rate) of manufacturing equipment and systems

high efficiency, flexibility and precision respectively reflect the two most important requirements of the manufacturing industry in the highly competitive market environment, namely, the agility of product production transformation and the continuous improvement of product quality

high precision

the precision of product parts directly affects its working performance, service life, energy consumption and noise. Therefore, the high precision of CNC machine tools is an inevitable result of market demand and technological development

analyzes the accuracy requirements of some key automotive parts, such as engine cylinder block, cylinder head, crankshaft, camshaft, connecting rod, carburetor, brake, shock absorber valve body, pump body, disc and mold, which have been significantly improved in recent decades

according to the statistics, the working accuracy of advanced CNC machine tools at home and abroad has been improved by an average of 10% every year from the 1980s to 2002, that is, the error has been reduced by about half every eight years. In this regard, some well-known machine tool companies in Europe, America and Japan are committed to scientific and technological innovation and research and development of new products, leading the development of CNC machine tool technology, such as the development of high-speed CNC milling machines in the automotive industry and aviation industry by Ingersoll and Wheeler Xile of Germany, the contribution of Makino of Japan to high-efficiency precision machining centers, and the development of heavy gantry five face milling machines by Waldrich of Germany, As well as the promotion of high-efficiency composite machining by the turning and milling center developed by Mazak company in Japan. Table 3 takes the medium-sized machining center with No. 40 tool handle as an example, and lists the significant progress in efficiency, precision and reliability of advanced products at home and abroad in recent years

based on this reality, in order to accelerate the revitalization of China's machine tool manufacturing industry, it is advisable to strengthen the research and development work in five aspects:

* take high-speed as the guide to improve the comprehensive performance of CNC machine tools

* accelerate the development of CNC machine tools to high efficiency, flexibility and precision, and promote the planning and implementation of acid grade precision machine tool engineering

* strengthen the development of multi-functional compound machining CNC machine tools to improve the machining accuracy and high efficiency flexibility of single piece and small and medium batch

* for medium and large batch production, developing rapid reconfigurable manufacturing system (RRMS) and reconfigurable machine tool (RMT) will be a reasonable solution

* develop networked manufacturing cells to adapt to the construction of digital enterprises

the following sections will briefly describe the above five development directions

taking high-speed as the guide

the high-speed of CNC machine tools is an important measure to improve its efficiency, flexibility and precision. It can not only improve the cutting capacity of the machine tool and shorten the auxiliary time, but also improve the chip forming process, reduce the feed per revolution of the cutter teeth and reduce the cutting force, which is helpful to improve the machining accuracy. By analyzing the development process of high-speed and high-precision of medium-sized machining centers, it can be concluded that the maximum speed and maximum feed speed of the spindle, which represent the high-speed cutting movement, continue to increase at the rate of doubling every 10 years, while the fast-moving speed (driven by ball screw and rotary servo motor) and the automatic tool change/worktable rotation speed, which represent the auxiliary time of the compression machine tool, basically double every 12~15 years, Since 1993, the new technology of direct drive with linear motor has been gradually popularized, which makes the fast moving speed of the machining center double that of the ball screw pair. However, the increase of spindle speed and feed speed will also cause some negative effects, which will increase the thermal deformation of machine tool structure and measurement system and the tracking error of position control. For this reason, a series of advanced control technologies, such as thermal error compensation, automatic tracking filter and drive system resonance suppression, feed rate forward control, position loop feedforward control and acceleration stability control, are developed by using information technology, so that the machining accuracy can be continuously improved under the condition of high-speed control

therefore, the development of high-speed can not simply pursue the increase of speed, but must consider the improvement of various constraints, so as not to achieve half the result with half the effort. In addition to the thermal error and control accuracy mentioned above, attention should also be paid to the static and dynamic stiffness, dynamic balance and tool performance of the machine tool structure

research and development of high-efficiency and precision CNC machine tools

at present, the CNC machine tools produced in China are still lack of high-efficiency and micron precision products, which shows the comparison between the processing demand of automotive parts and the current satisfaction of domestic machining centers, CNC milling machines, turning centers and CNC lathes, such as a box of tofu and a bag

most of the existing CNC machine tools can not meet the comprehensive requirements of the automobile manufacturing industry as a typical pillar industry for the high efficiency and precision of CNC manufacturing equipment

therefore, it is necessary to develop some NC manufacturing equipment that can give consideration to both high efficiency and high precision to meet the needs of processing key parts in manufacturing industries such as automobile, aviation, mold and military industry. Their performance is represented by area D in Figure 1. Because the machining accuracy of these NC manufacturing equipment is mainly within the micron level, Therefore, it can be called "level manufacturing equipment and technology research", also known as micro precision machine tool engineering.

the representative products in this regard include m-1250 horizontal high-precision machining center of Germany vadrich Jigen company, V56 vertical machining center of Japan Makino company and 1000 three-axis/five axis vertical machining center of Beijing machine tool Research Institute of China. Their positioning accuracy (ISO standard) Up to um, the comprehensive stiffness and metal removal capacity of the machine tool are twice as high as those of the traditional machine tools of the same type. The x107 hybrid drive horizontal machining center of Japan Yuanzhou company is only driven by linear motor for long stroke x-axis, which has a good cost performance ratio, and the MTBF marking the reliability reaches 5000h. Both have the characteristics of high efficiency and precision

develop compound machining CNC machine tools

multifunctional compound machining CNC machine tools are referred to as compound machine tools, or multi-functional machining or complete machining machine tools

the meaning of compound machine tool is to realize or complete all processing from blank to finished product on one machine tool as far as possible. Since the 1970s, there have been machining centers mainly used for boring and milling with rotating cutters as the main cutting motion, and turning centers mainly used for turning and milling with workpiece rotation as the main motion. These two types of multi-functional NC machine tools have played an important role in promoting the centralized process method of NC machine tools. However, for more complex parts, their functional scope is not enough to complete all processes from blank to finished product, so they can not fully improve the production efficiency under the conditions of single piece and medium and small batch production. Moreover, the transfer of workpieces among multiple machine tools increases the installation error, which is not conducive to the stability of processing accuracy

to this end, accelerate the development of compound CNC machine tools, improve the concentration of processes, and make the processing process chain intensive, which can improve the efficiency of multi variety single piece and small and medium batch processing. Compound CNC machine tools can reduce the waiting time and multiple loading and unloading time caused by the process conversion between different CNC machine tools to promote industry management innovation. Generally, these times account for 40%-60% of the whole production cycle of parts, and will still account for about 20% even under the condition of good information management. Therefore, the compound numerical control machine tool has obvious technical effect

composite CNC machine tools can be divided into the following two categories according to their structural characteristics:

* composite CNC machine tools that span machining categories: such machine tools mainly embody the combination of multiple functions such as tool rotary machining, workpiece rotary machining or special machining. Therefore, the machine tool structure should reflect the demand for different machining methods. At present, there are common turning and milling centers, milling centers and milling laser processing machines, etc

* compound CNC machine tool for multi face and multi axis linkage machining. Developing rapid reconfigurable manufacturing system

with the support of reconfigurable manufacturing technology, building a flexible manufacturing system that can adapt to mass and efficient production is a noteworthy development direction

develop networked manufacturing units

driven by the vigorous development of information technology, the manufacturing industry is facing the challenge of building an enterprise wide digitalization with the goal of improving competitiveness

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