At present, the development of CNC machine tools is changing with each passing day. High speed, high precision, compound, intelligent, open, parallel drive, networking, extreme and green have become the trend and direction of the development of CNC machine tools.
12 major development trends of CNC machine tools in the future
At present, the development of CNC machine tools is changing with each passing day. High speed, high precision, compound, intelligent, open, parallel drive, networking, extreme and green have become the trend and direction of the development of CNC machine tools.
As a manufacturing power, China mainly relies on comparative advantages in labor, price, resources and other aspects, and there is still a big gap with foreign counterparts in terms of product technological innovation and independent development. China's CNC industry cannot be content with the status quo. It should seize the opportunity to continue to develop, strive to develop its own advanced technology, increase technological innovation and talent training, improve the comprehensive service capabilities of enterprises, and strive to shorten the gap with developed countries. China strives to realize the transformation of CNC machine tool products from low-end to high-end, from primary product processing to high-precision product manufacturing as soon as possible, and realize the transformation from Made in China to Created in China, and from a manufacturing power to a manufacturing power.
1. High speed
With the rapid development of industries such as automobiles, national defense, aviation, and aerospace, as well as the application of new materials such as aluminum alloys, the requirements for high-speed processing of CNC machine tools are getting higher and higher.
（1） Spindle speed: The machine tool adopts an electric spindle (built-in spindle motor), and the maximum spindle speed reaches 200,000 r/min;
(2) Feed rate: When the resolution is 0.01μm, the maximum feed rate reaches 240m/min and can achieve precise processing of complex surfaces;
(3) Operation speed: The rapid development of microprocessors has provided a guarantee for the development of CNC systems in the direction of high speed and high precision. The CPU has been developed to 32-bit and 64-bit CNC systems, and the frequency has been increased to hundreds of megahertz and thousands of megahertz. Due to the great improvement in operation speed, when the resolution is 0.1μm and 0.01μm, a feed speed of up to 24-240m/min can still be obtained;
(4) Tool change speed: At present, the tool change time of advanced foreign machining centers is generally around 1s, and the highest has reached 0.5s. Chiron of Germany designed the tool magazine in a basket style, with the spindle as the axis and the tools arranged in a circle. The tool change time is only 0.9s.
2. High precision
The accuracy requirements of CNC machine tools are no longer limited to static geometric accuracy. The motion accuracy, thermal deformation and vibration monitoring and compensation of machine tools are increasingly valued.
(1) Improve the control accuracy of CNC system: adopt high-speed interpolation technology to achieve continuous feeding with small program segments, make CNC control units more refined, and adopt high-resolution position detection devices to improve position detection accuracy (Japan has developed an AC servo motor with a built-in position detector with 106 pulses/turn, and its position detection accuracy can reach 0.01μm/pulse). The position servo system adopts feedforward control and nonlinear control methods;
(2) Adopt error compensation technology: adopt reverse clearance compensation, screw pitch error compensation and tool error compensation technologies to comprehensively compensate for the thermal deformation error and spatial error of the equipment. The research results show that the application of comprehensive error compensation technology can reduce the processing error by 60% to 80%;
(3) Use grid inspection and improve the motion trajectory accuracy of the machining center, 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 stable for a long time, and it can complete a variety of processing tasks under different operating conditions and ensure the processing quality of parts.
3. Functional compounding
The meaning of compound machine tools is to realize or complete as much as possible the processing of multiple elements from blanks to finished products on one machine tool. According to its structural characteristics, it can be divided into two categories: process compound type and process compound type. Process compound machine tools include boring, milling and drilling compound-machining center, turning and milling compound-turning center, milling, boring, drilling and turning compound-compound machining center, etc.; process compound machine tools include multi-faceted multi-axis linkage machining compound machine tools and dual-spindle turning centers, etc. The use of composite machine tools for processing reduces the auxiliary time of workpiece loading and unloading, replacement and adjustment of tools, as well as the errors generated in the intermediate process, improves the processing accuracy of parts, shortens the product manufacturing cycle, improves production efficiency and the market responsiveness of manufacturers, and has obvious advantages over the traditional production method with dispersed processes.
The composite processing process has also led to the development of machine tools towards modularization and multi-axis. The latest turning processing center launched by Index Company in Germany is a modular structure. This processing center can complete a variety of processes such as turning, milling, drilling, gear hobbing, grinding, laser heat treatment, etc., and can complete the entire processing of complex parts. With the continuous improvement of modern mechanical processing requirements, a large number of multi-axis linkage CNC machine tools are becoming more and more popular among major companies. At the 2005 China International Machine Tool Exhibition (CIMT2005), domestic and foreign manufacturers exhibited various forms of multi-axis processing machine tools (including dual spindles, dual tool holders, 9-axis control, etc.) and five-axis high-speed gantry machining centers that can achieve 4-5 axis linkage, five-axis linkage high-speed milling centers, etc.
4. Intelligent control
With the development of artificial intelligence technology, the intelligence level of CNC machine tools is constantly improving in order to meet the development needs of flexible production and manufacturing automation in the manufacturing industry. Specifically, it is reflected in the following aspects:
(1) Adaptive control technology of machining process: by monitoring the cutting force, power, current, voltage and other information of the spindle and feed motor during the machining process, using traditional or modern algorithms for identification, the force, wear, damage status of the tool and the stability status of the machine tool machining can be identified, and the machining parameters (spindle speed, feed speed) and machining instructions can be adjusted in real time according to these conditions to keep the equipment in the best operating state, so as to improve the machining accuracy, reduce the machining surface roughness and improve the safety of equipment operation;
(2) Intelligent optimization and selection of machining parameters: the experience of process experts or technicians, the general and special laws of parts machining, and modern intelligent methods are used to construct an "intelligent optimization and selector of machining parameters" based on expert systems or models, and use it to obtain optimized machining parameters, so as to improve programming efficiency and machining technology level and shorten production preparation time;
(3) Intelligent fault self-diagnosis and self-repair technology: based on the existing fault information, modern intelligent methods are used to quickly and accurately locate the fault;
(4) Intelligent fault playback and fault simulation technology: It can fully record various information of the system, playback and simulate various errors and accidents that occur in CNC machine tools, so as to determine the causes of the errors, find solutions to the problems, and accumulate production experience;
(5) Intelligent AC servo drive device: An intelligent servo system that can automatically identify the load and automatically adjust the parameters, including an intelligent spindle AC drive device and an intelligent feed servo device. This drive device can automatically identify the rotational inertia of the motor and the load, and automatically optimize and adjust the control system parameters to achieve the best operation of the drive system;
(6) Intelligent 4M CNC system: In the manufacturing process, the integration of processing and detection is an effective way to achieve rapid manufacturing, rapid detection and rapid response. It integrates measurement (Measurement), modeling (Modelling), processing (Manufacturing), and machine operation (Manipulator) (i.e. 4M) into one system to achieve information sharing and promote the integration of measurement, modeling, processing, clamping, and operation.
5. Openness of the German system
(1) Open to future technologies: Since the software and hardware interfaces follow recognized standard protocols, with only a small amount of redesign and adjustment, the new generation of general software and hardware resources may be adopted, absorbed and compatible with the existing system, which means that the system development cost will be greatly reduced, and the system performance and reliability will continue to improve and have a long life cycle;
(2) Open to special user requirements: update products, expand functions, and provide various combinations of hardware and software products to meet special application requirements;
(3) Establishment of CNC standards: Internationally, a new CNC system standard ISO14649 (STEP-NC) is being studied and formulated to provide a neutral mechanism that does not depend on a specific system and can describe a unified data model throughout the product life cycle, thereby achieving standardization of product information throughout the manufacturing process and even in various industrial fields. Standardized programming languages are not only convenient for users to use, but also reduce labor consumption directly related to operating efficiency.
6. Drive parallelization
Parallel kinematic machine tools overcome the inherent defects of traditional machine tool serial mechanism, such as large moving parts, low system rigidity, tool feeding only along fixed guide rails, low operating freedom, insufficient equipment processing flexibility and maneuverability. A multi-rod parallel connection mechanism is used between the machine tool spindle (generally a moving platform) and the machine base (generally a static platform) to drive the platform supported by the rod system. By controlling the length of the rod in the rod system, the platform can obtain the corresponding degree of freedom of movement, which can realize multi-coordinate linkage CNC machining, assembly and measurement functions, and can better meet the processing of complex special parts. It has the advantages of high modularity, light weight and high speed of modern robots.
As a new type of processing equipment, parallel machine tools have become an important research direction of current machine tool technology and have been highly valued by the international machine tool industry. They are considered to be "the most meaningful progress in the machine tool industry since the invention of CNC technology" and "a new generation of CNC processing equipment in the 21st century".
7. Extreme (large-scale and miniaturization)
The development of national defense, aviation, aerospace and the large-scale development of basic industrial equipment such as energy require the support of large and high-performance CNC machine tools. Ultra-precision machining technology and micro-nano technology are strategic technologies in the 21st century. It is necessary to develop new manufacturing processes and equipment that can adapt to micro-size and micro-nano machining accuracy. Therefore, the demand for micro-machine tools including micro-cutting (turning, milling, grinding) machine tools, micro-electric machining machine tools, micro-laser machining machine tools and micro-presses is gradually increasing.
8. Information interaction networking
For companies facing fierce competition, it is very important to enable CNC machine tools to have two-way, high-speed network communication functions to ensure that information flows smoothly between various departments in the workshop. It can not only realize network resource sharing, but also realize remote monitoring, control, training, teaching, and management of CNC machine tools, and can also realize digital services for CNC equipment (remote diagnosis and maintenance of CNC machine tool faults, etc.).
For example, Japan's Mazak company launched a new generation of machining centers equipped with an external device called an information tower (e-Tower), including computers, mobile phones, external and internal cameras, etc., which can realize voice, graphic, video and text communication fault alarm display, online help troubleshooting and other functions. It is an independent and 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 has become inevitable. Representative new functional components include:
(1) High-frequency electric spindle: High-frequency electric spindle is the integration of high-frequency motor and spindle components. It has a series of advantages such as small size, high speed, and stepless speed regulation. It has been widely used in various new CNC machine tools;
(2) Linear motor: In recent years, the application of linear motors has become increasingly widespread. Although its price is higher than that of traditional servo systems, due to the application of key technologies such as load change disturbance, thermal deformation compensation, magnetic isolation and protection, the mechanical transmission structure has been simplified and the dynamic performance of the machine tool has been improved. For example, the 1FN1 series three-phase AC permanent magnet synchronous linear motors produced by Siemens have begun to be widely used in high-speed milling machines, machining centers, grinders, parallel machine tools, and machine tools with high requirements for dynamic performance and motion accuracy; the XHC horizontal machining center of Germany's EX-CELL-O company uses two linear motors for three-way drive;
(3) Electric ball screw: The electric ball screw is an integration of a servo motor and a 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, CNC machine tools have added CNC systems and corresponding monitoring devices, and use a large number of electrical, hydraulic and electromechanical devices, which can easily lead to an increased 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 have relatively complex surfaces and long processing cycles, requiring an average failure-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, strictly manufacture and clarify the reliability goals, and analyze the failure mode through maintenance and find out the weak links.
The average trouble-free time of foreign CNC systems is more than 70,000 to 100,000 hours, while the average trouble-free time of domestic CNC systems is only about 10,000 hours. The average trouble-free working time of foreign complete machines is more than 800 hours, while the highest in China is only 300 hours.
11. Greening of the processing process
With the increasingly stringent 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, machine tools that do not use or use less coolant and achieve dry cutting and semi-dry cutting energy saving and environmental protection have continued to appear and are constantly developing. 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, audio and video and communication technology, enabling computers to have the ability to comprehensively process sound, text, image and video information, and therefore also puts forward graphical requirements for user interfaces. Reasonable and user-friendly user interface greatly facilitates the use of non-professional users. People can operate through windows and menus, which is convenient for blueprint programming and fast programming, three-dimensional color stereo dynamic graphics display, graphic simulation, graphic dynamic tracking and simulation, different directions of view and local display scaling function.
In addition, it is widely used in the field of CNC technology.
Media technology can achieve integrated and intelligent information processing, and is applied to real-time monitoring systems and fault diagnosis of production site equipment, production process parameter monitoring, etc., so it has great application value.
Domestic CNC machine tools lack core technology, and basically rely on imports from high-performance CNC systems to key functional components. Even though some domestic manufacturers have created their own brands with difficulty in recent years, the reliability of their product functions and performance is still somewhat behind foreign products. In recent years, domestic CNC machine tool manufacturers have obtained some advanced CNC technologies through technology introduction, mergers and acquisitions at home and abroad, and foreign procurement, but lack research on basic technologies such as machine tool structure and precision, reliability, and humanized design, and neglect the cultivation of independent development capabilities. The technical level, performance and quality of domestic CNC machine tools are still far behind those of foreign countries, and it is also difficult to be recognized by most users.
Some domestic CNC machine tool manufacturers do not pay enough attention to the improvement of overall process and manufacturing level. The processing methods are basically based on ordinary machine tools and inefficient tools. Assembly and debugging are completely manual. The processing quality cannot be stabilized and improved under the pressure of production progress. In addition, many domestic CNC machine tool manufacturers still use the original manual ledger management method for production management. The low process level and management efficiency make it impossible for enterprises to form a sufficient production scale. For example, foreign machine tool manufacturers can install and adjust products every week, while the domestic production cycle is too long and difficult to control. Therefore, while introducing technology, we should pay attention to strengthening our own process technology transformation and management level improvement.
Due to the rapid development of the CNC machine tool industry, some companies ignore long-term interests, do not pay enough attention to improving their comprehensive service level, and even lack a real understanding of services. They only focus on sales but not pre-sales and after-sales services. Some companies send personnel who lack sufficient understanding of the CNC machine tools they produce, do not know how to use or use CNC machine tools well, and cannot guide users to use the machine tools well; some lack a basic understanding of advanced and efficient tools and cannot provide better process solutions. Naturally, users lack confidence in manufacturers.
The manufacturer's service should start with studying the user's processing products, processes, production types, and quality requirements, helping users select equipment, recommending advanced processes and auxiliary tools, and equipping professional training personnel and a good training environment to help users maximize the benefits of machine tools and process high-quality final products. Only in this way can the manufacturer gradually gain recognition from users and increase the market share of domestic CNC machine tools.