The next 12 development trends of CNC machine tools

1. High speed

With the rapid development of automotive, national defense, aviation, aerospace and other industries and the application of new materials such as aluminum alloy, the requirements for high-speed CNC machine tool processing are getting higher and higher.

(1) Spindle speed: the machine adopts electric spindle (built-in spindle motor), and the maximum spindle speed is 200000r/min;

(2) Feed rate: When the resolution is 0.01μm, the maximum feed rate reaches 240m/min and the complex surface can be accurately processed;

6 (3) Computing speed: The rapid development of microprocessors provides a guarantee for the development of CNC systems to high-speed and high-precision direction, and the development of CPU has been developed to 32-bit and 64-bit CNC systems, and the frequency has been increased to hundreds of megahertz, thousands of megahertz. Due to the greatly improved operation speed, the feed speed of up to 24-240m /min can be obtained when the resolution is 0.1μm and 0.01μm.

(4) Tool change speed: At present, the tool exchange time of foreign advanced machining centers has generally been about 1s, and the high has reached 0.5s. The German Chiron company designed the knife library as a basket style, with the spindle as the axis, the tool is arranged in the circle, and the knife to the knife change time is only 0.9s.



2. High precision

CNC machine tool accuracy requirements are now not limited to static geometric accuracy, machine tool motion accuracy, thermal deformation and vibration monitoring and compensation more and more attention.



(1) Improve the control accuracy of CNC system: High-speed interpolation technology is used to achieve continuous feed with tiny program segments, so that the CNC control unit is refined, and high-resolution position detection device is used to improve the position detection accuracy (Japan has developed an AC servo motor equipped with 106 pulse/revolution built-in position detector, the position detection accuracy can reach 0.01μm/ pulse). The position servo system adopts feedforward control and nonlinear control methods.

(2) The use of error compensation technology: the use of reverse clearance compensation, screw pitch error compensation and tool error compensation technology, the thermal deformation error and space error of the equipment comprehensive compensation. The results show that the application of comprehensive error compensation technology can reduce the machining error by 60% ~ 80%.

(3) Using the grid to check and improve the accuracy of the machining center's motion trajectory, and predict the machining accuracy of the machine tool through simulation to ensure the positioning accuracy and repeated positioning accuracy of the machine tool, so that its performance is long-term stable, can complete a variety of processing tasks under different operating conditions, and ensure the processing quality of parts.



3. Functional compound

The meaning of composite machine refers to the realization or completion of a variety of elements from blank to finished product processing on a single machine tool. According to its structural characteristics, it can be divided into two categories: process compound and process compound. Process complex machine tools such as boring, milling and drilling complex - machining center, turning and milling complex - turning center, milling, boring and drilling complex - composite machining center, etc. Process compound machine tools, such as multi-sided multi-axis joint machining of composite machine tools and double spindle turning centers. The use of composite machine tools for processing, reducing the workpiece loading and unloading, replacing and adjusting the auxiliary time of the tool and the error generated in the middle process, improve the parts processing accuracy, shorten the product manufacturing cycle, improve the production efficiency and the manufacturer's market response ability, compared with the traditional process dispersion of the production method has obvious advantages.



The compounding of the processing process has also led to the development of modular and multi-axial machine tools. The latest turning machining center launched by German Index company is a modular structure, which can complete a variety of processes such as turning, milling, drilling, hobbing, grinding, laser heat treatment, etc., and can complete the entire processing of complex parts. With the continuous improvement of modern machining requirements, a large number of multi-axis CNC machine tools are increasingly welcomed by major enterprises. In the 2005 China International Machine Tool Exhibition (CIMT2005), domestic and foreign manufacturers exhibited different forms of multi-axis machining machine tools (including double spindle, double tool holder, 9-axis control, etc.) and can achieve 4-5 axis linkage five-axis high-speed portal machining center, five-axis linkage high-speed milling center, etc.



4. Intelligent control

With the development of artificial intelligence technology, in order to meet the development needs of manufacturing production flexibility and manufacturing automation, the intelligence level of CNC machine tools is constantly improving. It is reflected in the following aspects:

(1) Process adaptive control technology: By monitoring the cutting force, spindle and feed motor power, current, voltage and other information in the processing process, the use of traditional or modern algorithms to identify the force, wear, damage state of the tool and the stability state of the machine tool processing, and according to these states real-time adjustment of processing parameters (spindle speed, feed speed) and processing instructions, Make the equipment in the best running state to improve the machining accuracy, reduce the machining surface roughness and improve the safety of the equipment operation;

(2) Intelligent optimization and selection of processing parameters: Based on the experience of process experts or technicians, the general and special laws of parts processing, the "intelligent optimization and selection of machining parameters" based on expert system or model is constructed with modern intelligent methods, and the optimized machining parameters are obtained by using it, so as to achieve the purpose of improving programming efficiency and processing technology level and shortening production preparation time.

(3) Intelligent fault self-diagnosis and self-repair technology: according to the existing fault information, the application of modern intelligent methods to achieve rapid and accurate fault location;

(4) Intelligent fault playback and fault simulation technology: it can completely record all kinds of information of the system, playback and simulation of various errors and accidents of CNC machine tools, in order to determine the causes of errors, find out solutions to problems, and accumulate production experience;

(5) Intelligent AC servo drive device: intelligent servo system that can automatically identify the load and automatically adjust the parameters, including intelligent spindle AC drive device and intelligent feed servo device. The drive device can automatically identify the moment of inertia of the motor and the load, and automatically optimize and adjust the parameters of the control system, so that the drive system can get the best operation.

(6) Intelligent 4M numerical control system: In the Manufacturing process, the integration of processing and testing is an effective way to achieve rapid manufacturing, rapid detection and rapid response, which integrates Measurement, Modelling, manufacturing and machine operation in one system. Realize information sharing and promote the integration of measurement, modeling, processing, clamping and operation.



5. Open the system

(1) Open to future technology: Because the hardware and software interfaces follow the recognized standard protocols, only a small amount of redesign and adjustment, a new generation of general hardware and software resources may be adopted, absorbed and compatible by the existing system, which means that the development cost of the system will be greatly reduced and the system performance and reliability will continue to improve and in a long life cycle;

(2) Open to the special requirements of users: update products, expand functions, and provide various combinations of hardware and software products to meet special application requirements;

(3) The establishment of CNC standards: the international is studying and developing a new CNC system standard ISO14649 (STEP-NC) to provide a neutral mechanism that does not rely on specific systems, and can describe a unified data model throughout the product life cycle, so as to achieve the standardization of product information throughout the manufacturing process and even various industrial fields. The standardized programming language is convenient for users to use and reduces labor consumption directly related to operational efficiency.



6. Drive parallel

The parallel moving machine tool overcomes the inherent defects of the traditional machine tool series mechanism, such as large moving parts, low system stiffness, cutting tools can only feed along a fixed guide rail, low degree of freedom of operation, equipment processing flexibility and insufficient mobility, etc., and adopts multi-bar parallel connecting mechanism drive between the machine tool spindle (generally a moving platform) and the machine base (generally a static platform). By controlling the length of the rod in the rod system, the platform supported by the rod system can obtain the corresponding freedom of movement, which can realize a variety of functions of multi-coordinate linkage CNC machining, assembly and measurement, and can meet the processing of complex special parts, and has the advantages of high modularity, light weight and fast speed of modern robots. As a new type of processing equipment, parallel machine tool has become an important research direction of the current machine tool technology, which has been highly valued by the international machine tool industry, and is considered to be "the most meaningful progress in the machine tool industry since the invention of numerical control technology" and "a new generation of CNC machining equipment in the 21st century".



7. Extreme (large and miniaturized)

The development of national defense, aviation, aerospace industry and the large-scale equipment of basic industries such as energy require the support of large and good performance CNC machine tools. The ultra-precision machining technology and micro and nano technology is the strategic technology of the 21st century, the need to develop new manufacturing processes and equipment that can adapt to the micro size and micro and nano processing precision, so the demand for micro machine tools including micro cutting (turning, milling, grinding) machine tools, micro electric machining machines, micro laser processing machines and micro presses is gradually increasing.



8. Information interaction and networking

For enterprises facing fierce competition, it is very important to make CNC machine tools have two-way, high-speed networking communication functions to ensure that the information flow is unimpeded between various departments in the workshop. It can realize network resource sharing, remote monitoring, control, training, teaching, management of CNC machine tools, and digital services of CNC equipment (remote diagnosis, maintenance, etc.). For example, the Japanese Mazak company launched a new generation of machining center equipped with a called information tower (e-Tower) of external equipment, including computers, mobile phones, outside and inside the camera, etc., to achieve voice, graphics, video and text communication fault alarm display, online help troubleshoot and other functions, is an independent, self-managed manufacturing unit.



9. New functional components

In order to improve the performance of CNC machine tools in all aspects, the application of new functional components with high precision and high reliability becomes inevitable. Typical new features include:

(1) high-frequency electric spindle: high-frequency electric spindle is the integration of high-frequency motor and spindle components, with a series of advantages such as small size, high speed, stepless speed regulation, etc., has been widely used in various new CNC machine tools;

(2) Linear motor: In recent years, the application of linear motor is becoming more and more widely, although its price is higher than the traditional servo system, but due to the application of key technologies such as load change disturbance, thermal deformation compensation, magnetic insulation and protection, the mechanical transmission structure is simplified, and the dynamic performance of the machine tool has been improved. For example, the 1FN1 series three-phase AC permanent magnet synchronous linear motor produced by Siemens has been widely used in high-speed milling machines, machining centers, grinding machines, parallel machine tools and machine tools with high dynamic performance and motion accuracy requirements. The XHC horizontal machining center of Germany EX-CELL-O adopts two linear motors for three-way drive.

(3) ball screw: ball screw is the integration of servo motor and ball screw, which can greatly simplify the structure of CNC machine tools, and has a series of advantages such as fewer transmission links and compact structure.



10. High reliability

Compared with traditional machine tools, numerical control system and corresponding monitoring devices are increased, and a large number of electrical, hydraulic and electromechanical devices are applied, which is easy to increase the probability of failure. The fluctuation and interference of industrial power grid voltage are extremely unfavorable to the reliability of CNC machine tools, and the parts processed by CNC machine tools are more complex, and the processing cycle is long, requiring an average trouble-free time of more than 20,000 hours. In order to ensure the high reliability of CNC machine tools, it is necessary to carefully design the system, strict manufacturing and clear reliability objectives, and analyze the failure mode and find the weak link through maintenance. The average trouble-free time of foreign CNC systems is more than 7 ~ 100,000 hours, the average trouble-free time of domestic CNC systems is only about 10,000 hours, and the average trouble-free working time of foreign machines is more than 800 hours, while the domestic maximum is only 300 hours.



11. Green processing

With the increasingly strict environmental and resource constraints, the greening of manufacturing and processing is becoming more and more important, and China's resource and environmental problems are particularly prominent. Therefore, in recent years, without or less use of coolant, to achieve dry cutting, semi-dry cutting energy saving and environmental protection machine tools continue to appear, and in continuous development. In the 21st century, the general trend of green manufacturing will accelerate the development of various energy-saving and environmentally friendly machine tools and occupy more world markets.



12. Application of multimedia technology

Multimedia technology integrates computer, sound and image technology and communication technology, so that the computer has the ability to comprehensively process sound, text, image and video information, so it also puts forward the graphical requirements for the user interface. Reasonable humanized user interface greatly facilitates the use of non-professional users, people can operate through the window and menu, easy to blueprint programming and rapid programming, three-dimensional color three-dimensional dynamic graphics display, graphics simulation, graphics dynamic tracking and simulation, different directions of the view and local display scale scaling function. In addition, the application of multimedia technology in the field of numerical control technology can achieve integrated and intelligent information processing, applied to real-time monitoring systems and production site equipment fault diagnosis, production process parameter monitoring, etc., so it has great application value.



Domestic CNC machine tools lack of core technology, from high-performance CNC systems to key functional components are basically dependent on imports, even in recent years, some domestic manufacturers have struggled to create their own brand, but the reliability of its product function, performance is still a certain gap with foreign products. In recent years, domestic CNC machine tool manufacturers have obtained some advanced CNC technology through technology introduction, mergers and acquisitions at home and abroad and foreign procurement, but the lack of machine tool structure and accuracy, reliability, humanized design and other basic technology research, ignoring the cultivation of independent development capabilities, the technical level of domestic CNC machine tools, performance and quality and foreign countries still have a big gap. It is also difficult to get the approval of most users.



Some domestic CNC machine tool manufacturers do not pay enough attention to the improvement of the overall process and manufacturing level, the processing means are basically ordinary machine tools and inefficient tools, assembly and debugging are completely manual, and the processing quality can not be stable and improved under the pressure of the production schedule. In addition, the production management of many domestic CNC machine tool manufacturers is still in use of the original manual ledger management mode, and the low technical level and management efficiency make the enterprise unable to form enough production scale. For example, foreign machine tool manufacturers can install and transfer products every week, and the domestic production cycle is too long and difficult to control. Therefore, we should pay attention to strengthen our own technological transformation and management level while introducing technology.