The machine tool refers to the machine used to manufacture the machine, also known as the “work machine” or “machine tool”.
Early machine tools appeared as early as the 15th century. In 1774, a barrel boring machine invented by the British Wilkinson was considered the first real machine tool in the world. It solved the problem of machining the cylinder of the Watt steam engine.
In the 18th century, various types of machine tools appeared and developed rapidly, such as threaded lathes, gantry type machine tools, horizontal milling machines, gear hobbing machines, etc., which laid the foundation for manufacturing tools for the industrial revolution and the establishment of modern industry.
In 1952, the world’s first numerical control (numerical control, NC) machine tool came out at the Massachusetts Institute of Technology in the United States, marking the beginning of the machine tool numerical control era. A CNC machine tool is a machine tool equipped with a digital control system (“numerical control system” for short). The numerical control system includes two parts: a numerical control device and a servo device. The current numerical control device is mainly realized by electronic digital computers, also known as computerized numerical control, CNC) device.
CNC machine tools can be classified according to processing technology, motion mode, servo control mode, machine tool performance, etc. Traditionally, CNC machine tools are usually divided into two categories: CNC metal cutting machine tools and CNC metal forming machine tools based on the characteristics of the surface forming process of the processed object (part).
In recent years, due to the increasing application of new materials in complex products (such as airplanes, automobiles, aero engines, etc.), the materials of the processed parts of CNC machine tools are no longer limited to metal materials, but have expanded to non-metallic materials such as composite materials and ceramic materials. The processing technology also includes special processing methods.
In addition, from the perspective of function and performance, CNC machine tools can be divided into three categories: economical, mid-range (or popular), and high-end. At present, there is no clear and unified definition of high-end CNC machine tools. The author believes that: high-end CNC machine tools are CNC machine tools with high-performance, intelligent and high-value characteristics and reaching corresponding functions and performance technical indicators. High-end CNC machine tools are a typical representative of the technical level of the CNC machine tool industry and the competitiveness of the equipment manufacturing industry.
The Evolution History Of CNC Machine
As a “worker machine”, the machine tool has been accompanied by the development of industrialization throughout the process. After the industrial revolution in the 18th century, machine tools evolved with the development of different industrial eras and showed the technical characteristics of each era. As shown in Figure 1, corresponding to the era of Industry 1.0 to Industry 4.0, machine tools have evolved from mechanical drive/manual operation (machine tool 1.0), electric drive/digital control (machine tool 2.0) to computer digital control (machine tool 3.0), and are moving towards cyber The evolution and development of cyber-physical machine/cloud solution (machine tool 4.0).
The development process of CNC machine tools has experienced several important turning points.
In 1952, the world’s first CNC machine tool was successfully developed at the Massachusetts Institute of Technology in the United States. This was a revolutionary leap in manufacturing technology. The CNC machine tool adopts digital programming, program execution, servo control and other technologies to realize the automatic control of the trajectory movement and operation of the machine tool by the digital processing program compiled in accordance with the part pattern. Since then, the NC technology has enabled the development of machine tools and electronics, computers, control, information and other technologies. Inseparable. Subsequently, in order to solve the automatic problem of NC programming, automatic programming tools (APT) and methods that use computers instead of manual became key technologies, and computer-aided design/manufacturing (CAD/CAM) technology has also been rapidly developed and popularized. It can be said that manufacturing digitization began with the birth of CNC machine tools and their core digital control technology.
It is precisely because of the several major characteristics of CNC machine tools and CNC technology at the beginning of their birth-digital control ideas and methods, “soft (pieces)-hard (pieces)” combination, “machine (mechanical)-electrical (sub)- Control (control)-information (information) “multi-disciplinary cross, so the subsequent major progress of CNC machine tools and CNC technology has been directly related to the development of electronic technology and information technology (Figure 2).
The earliest numerical control device used electronic vacuum tubes to form a computing unit. The transistor was invented in the late 1940s, and integrated circuits were introduced in the late 1950s. In the early 1960s, electronic digital computers using integrated circuits and large-scale integrated circuits appeared. The breakthrough in capability, miniaturization and reliability brought the first inflection point for the development of CNC machine tool technology-from discrete component-based digital control (NC) to computer digital control (CNC), CNC machine tools also began to enter Actual industrial production applications.
The development of PC has brought a second inflection point to CNC machine tool technology. In the 1980s, IBM introduced a personal computer (PC) with a 16-bit microprocessor, which enabled the development of numerical control devices (including hardware and software) by special-purpose manufacturers in the past and moved towards general PC-based computer numerical control. At the same time, an open-architecture CNC system has also emerged to promote the development of numerical control technology to a higher level of digitization and networking. On this basis, new technologies such as high-speed machine tools, virtual axis machine tools, and compound processing machine tools have been rapidly iterated and merged. application.
Since the 21st century, the third turning point of CNC machine tools has begun to become clear. Intelligent numerical control technology has also begun to sprout. With the development of a new generation of information technology and a new generation of artificial intelligence technology, new technologies such as intelligent sensing, Internet of Things, big data, digital twins, cyber-physical systems, cloud computing and artificial intelligence, etc. Deeply integrated with CNC technology, CNC technology will usher in a new inflection point or even a new leap-towards a new generation of intelligent CNC that integrates cyber physics.
In this process, the machining efficiency and machining accuracy of machine tools have been continuously improved. The continuous progress and application of advanced manufacturing technology have greatly shortened processing time and improved processing efficiency. Figure 7a is a widely quoted graph that shows the development of advanced manufacturing technology and the progress of processing time (efficiency). From the perspective of development trends, on the one hand, from 1960 to 2020, the total processing time (including cutting time, auxiliary time and preparation time) in manufacturing production has been reduced to 16% of the original processing time, that is, the processing efficiency has been significantly improved; on the other hand, On the one hand, the proportions of “cutting time, auxiliary time, and preparation time” are gradually becoming the same.
Therefore, to improve processing efficiency in the future, not only must focus on the optimization and improvement of process methods and increase the degree of automation, but also the production The management’s digital, networked and intelligent perspectives effectively shorten the waiting time. Figure 7b is the forecast of machining accuracy that can be achieved by different machine tools by Taniguchi in the 1980s (the dashed line of accuracy improvement from 2000 to 2020 in the figure is added by the author). It can be seen that various machining The development of process methods and machine tool (or equipment) technology has brought continuous improvement in processing accuracy, but the field of mechanical processing is different from the field of integrated circuit manufacturing. Doubled in 24 months), its accuracy improvement is a long-term technology accumulation and continuous iteration process (for example: precision machining has increased by an order of magnitude of accuracy for more than 20 years).
The development trend of CNC machine tool technology
In terms of the main development trends in the future, the author believes that CNC machine tool technology presents a development trend of high performance, multi-function, customization, intelligence and green, namely:
- (1) High performance. In the development process of CNC machine tools, we have been striving to pursue higher machining accuracy, cutting speed, production efficiency and reliability. In the future, CNC machine tools will achieve high-speed and high-precision direct interpolation of complex curves and surfaces and servo control with high dynamic response through further optimized machine structure, advanced control systems and efficient mathematical algorithms; through digital virtual simulation, optimized static Dynamic stiffness design, thermal stability control, online dynamic compensation and other technologies greatly improve reliability and accuracy retention.
- (2) Multifunctional. From the combination of different cutting processes (such as turning and milling, milling) to the combination of different forming methods (such as the combination or mixing of forming methods such as additive manufacturing, subtractive manufacturing and isomaterial manufacturing), CNC machine tools and robots “machine-machine” Development in the direction of integration and collaboration; from the traditional serial process chain of “CAD-CAM-CNC” to the one-step processing direction of “CAD+CAM+CNC integration” based on 3D solid models; from the networking of “machine-machine” interconnection to The development of big data processing supported by “human-machine-thing” interconnection and edge/cloud computing.
- (3) Customization. According to user needs, provide customized development in machine tool structure, system configuration, professional programming, cutting tools, on-machine measurement, etc., and provide customized services in processing technology, cutting parameters, fault diagnosis, operation and maintenance, etc. Technologies such as modular design, reconfigurable configuration, networked collaboration, software-defined manufacturing, and mobile manufacturing will provide technical support for the realization of customization.
- (4) Intelligent. Through sensors and standard communication interfaces, the machine tool status and processing process signals and data are sensed and acquired. The processing process is learned through transformation processing, modeling analysis and data mining, and information and instructions supporting optimal decision-making are formed. The monitoring, forecasting and control of the processing process meet the requirements of high-quality, high-efficiency, flexible and adaptive processing. “Perception, interconnection, learning, decision-making, and self-adaptation” will become the main functional characteristics of CNC machine tools. Processing big data, industrial IoT, digital twins, edge computing/cloud computing, deep learning, etc. will strongly promote future smart machine tools The development and progress of technology.
- (5) Greening. The technology faces the needs of future sustainable development, with eco-friendly design, lightweight structure, energy-saving and environmentally friendly manufacturing, optimized energy efficiency management, clean cutting technology, pleasant human-machine interface and product life cycle green services.
Cutting machine tools are various processes (such as turning, milling, boring, drilling, grinding, etc.) that use tools or abrasives to act on the workpiece through mechanical energy. The essential problems can be attributed to two points. One is the use of What energy removes material? Second, how to control energy use? As mentioned at the beginning of this article, machine tool 1.0 uses steam power to directly provide mechanical energy to the machine tool to realize various cutting processes. The control method is manual control; machine tool 2.0 converts electrical energy into mechanical energy. Drive machine tools and bring the emergence of digitally controlled machine tools. The control method is automatic control; Machine Tool 3.0 is a computer numerical control machine tool brought by computer and information technology. It changes the machine tool control method and production organization method to make it digital and networked. .
Looking to the future, machine tool 4.0 will face new revolutionary changes. The first is that the energy directly used in the material removal process changes from mechanical energy to mechanical energy, electrical energy, light energy, chemical energy and other energy fields and their combinations. The second is the control method of energy use. On the one hand, intelligent control is the most important feature and trend of the recent development of machine tools in the future. It makes machine tools higher (precision), faster (efficiency), stronger (function), and more economical (green). ); On the other hand, the upcoming quantum computing and quantum computers, just as electronic computers brought a revolutionary leap to CNC machine tools, redefine a generation of CNC machine tools and give birth to new principles and concepts of CNC machine tools and production processes.
As a working machine, machine tools have provided manufacturing tools and methods for the industrial revolution and modern industrial development for many years; the future industrial development and the progress of human civilization are still inseparable from the support and promotion of CNC machine tools. Looking forward to the future, a new round of industrial revolution brings new challenges and opportunities to the development of CNC machine tools. The integration of advanced manufacturing technology with a new generation of information technology and a new generation of artificial intelligence will also bring technological innovation, product upgrades and industrial upgrades to CNC machine tools. Provided with technical support, CNC machine tools will move towards high performance, multi-function, customization, intelligence and greening, and embrace the new quantum computing technology of the future, and provide stronger, more convenient and more convenient for the new industrial revolution and the progress of human civilization. Effective manufacturing tools.
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