What is the development trend of CNC machine tools in the futur

• Posted by CNC LATHING April 26, 2021 - Filed in Other - 1,187 views

  At present, the development of CNC machine tool is changing rapidly. The development trend and direction of NC machine tool are high speed, high precision, compound, intelligent, open, parallel drive, network, extreme and green. As a manufacturing country, China mainly relies on the comparative advantages of labor, price and resources, while the gap between China and foreign counterparts in the field of technological innovation and independent development of products is still large. China's CNC industry cannot be settled in the current situation. It should seize the opportunity to develop continuously, strive to develop its own advanced technology, increase the strength of technological innovation and talent training, improve the comprehensive service ability of enterprises and try to shorten the gap between China and developed countries. We will strive to realize the transformation of CNC machine tool products from low-end to high-end, from primary product processing to high-end product manufacturing, and realize the transformation from Chinese manufacturing to Chinese creation, from a manufacturing country to a manufacturing power.

   

  1. High speed

  With the rapid development of automobile, national defense, aviation, aerospace and other industries and the application of new materials such as aluminum alloy, the requirements of high speed machining of CNC machining services tools are becoming higher and higher.

  (1) Spindle speed: the machine adopts the electric spindle (internal spindle motor), and the maximum speed of the spindle reaches 200000r / min;

  (2) Feed rate: at resolution 0.01 μ At m, the maximum feed rate reaches 240m/min and the precise machining of complex profile can be obtained;

  (3) Operation speed: the rapid development of microprocessor provides guarantee for the development of CNC system to high speed and high precision. The CPU has developed to 32-bit and 64 bit CNC system, with frequency increased to hundreds of megahertz and thousands of megahertz. Because of the great improvement of the operation speed, the resolution is 0.1 μ m、0.01 μ The feed speed can be obtained up to 24-240m/min at M;

  (4) Tool change speed: at present, the tool exchange time of foreign advanced machining centers is about 1 s, and the high one is 0.5s. The tool magazine is designed as basket style by Chiron company in Germany, with the spindle as the axis, and the tool is arranged in the circle. The tool changing time from the tool to the tool is only 0.9s.

   

  1. High precision

  The requirement of NC machine tool precision is not limited to the static geometry precision. The motion precision, thermal deformation and vibration monitoring and compensation of the machine tool are paid more and more attention.

  (1) Improve the control accuracy of CNC system: adopt high-speed interpolation technology to realize continuous feed with micro program section, make CNC control unit fine, and adopt high resolution position detection device to improve position detection accuracy (the AC servo motor with 106 pulse / turn internal position detector has been developed in Japan, and its position detection accuracy can reach 0.01 μ M/ pulse), position servo system adopts feedforward control and nonlinear control;

  (2) The error compensation technology is adopted: the reverse clearance compensation, screw pitch error compensation and tool error compensation are used to compensate the thermal deformation error and space error of the equipment. The results show that the application of the integrated error compensation technology can reduce the machining error by 60% ~ 80%;

  (3) The accuracy of the machining center is improved by grid checking and simulation. The machining accuracy of the machine tool is predicted by simulation, so as to ensure the positioning accuracy and repeated positioning accuracy of the machine tool, make its performance stable for a long time, and can complete various machining tasks under different operating conditions and ensure the machining quality of parts.

   

  1. Functional compounding

  The meaning of compound machine tool is to realize or complete the processing of various elements from blank to finished product on a machine tool. According to its structural characteristics, it can be divided into two types: process compound type and process composite type. The process compound machine tools such as boring and milling compound machining center, turning compound turning center, milling and boring drill compound compound machining center, etc; The process compound machine tools such as multi-faceted and multi axis linkage machining and double spindle turning center, etc. The composite machine tool is used to process, which reduces the auxiliary time of workpiece loading and unloading, replacement and adjustment of tools and the errors in the middle process, improves the machining accuracy of parts, shortens the manufacturing cycle of products, improves the production efficiency and the market reaction capacity of the manufacturer. It has obvious advantages over the traditional process dispersion production methods.

   

  The compounding of machining process also leads to the development of modular and multi axis machine tools. The latest Turning Center launched by German index company is modular structure. It can complete various processes such as turning, milling, drilling, hobbing, grinding, laser heat treatment, etc., and can complete all the processing of complex parts. With the increasing requirements of modern machining, a large number of multi axis CNC machine tools are more and more popular with the major enterprises. At CIMT2005, manufacturers at home and abroad displayed various multi axis machining machines (including double spindle, double tool holder, 9 axis control, etc.) and five axis high-speed gate machining center and five axis linkage high-speed milling center which can realize 4-5 axis linkage.

   

  1. Intelligent control

  With the development of artificial intelligence technology, in order to meet the development demand of manufacturing flexibility and manufacturing automation, the intelligent degree of CNC machine tools is constantly improving. Specifically reflected in the following aspects:

   

  (1) Adaptive control technology in machining process: by monitoring cutting force, power, current and voltage of main shaft and feed motor in the process of machining, traditional or modern algorithms are used to identify the force, wear, damage and stability of machining tool, and adjust processing parameters (spindle speed, speed, etc.) in real time Feed speed) and processing instruction, so that the equipment is in the best operation state, in order to improve the processing accuracy, reduce the surface roughness and improve the safety of the equipment operation;

  (2) Intelligent optimization and selection of processing parameters: by using modern intelligent method, the experience of process experts or technicians, general and special rules of parts processing are constructed by using modern intelligent method, and the "intelligent optimization and selector of processing parameters" based on expert system or model are constructed. The optimized machining parameters can be obtained by using it, so as to improve the programming efficiency and the level of processing technology The purpose of shortening the production preparation time;

  (3) Intelligent fault self diagnosis and self repair technology: according to the existing fault information, the modern intelligent method is applied to realize the fast and accurate fault location;

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

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

  (6) Intelligent 4m CNC system: in the manufacturing process, the integration of processing and detection is an effective way to realize rapid manufacturing, rapid detection and rapid response. The four (namely 4m) measurement, modeling, manufacturing and machine operation are integrated into one system to realize information sharing, and promote measurement, modeling, processing Integration of clamping and operation.

   

  1. Opening up of the German system

  (1) Open to the future technology: because the software and hardware interfaces follow the accepted standard protocol, only a small amount of redesign and adjustment is required, the new generation of general software and hardware resources may be adopted, absorbed and compatible by the existing systems, which means that the development cost of the system will be greatly reduced, and the system performance and reliability will be continuously improved and will be in a long life cycle;

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

  (3) Establishment of CNC standard: a new CNC machining system standard iso14649 (STEP-NC) is being studied and developed in the world to provide a neutral mechanism that does not depend on specific system, and can describe the unified data model of the whole product life cycle, so as to realize the standardization of product information in the whole manufacturing process and in various industrial fields. The standardized programming language is convenient for users to use, and reduces the labor consumption directly related to the operation efficiency.

   

  1. Drive parallelization

  Parallel motion machine tool overcomes the inherent defects of the traditional machine tool series mechanism, such as large quality of moving parts, low system rigidity, tool feeding along fixed guide rail, low degree of freedom of operation, insufficient flexibility and mobility of equipment processing. The multi-bar parallel connection mechanism is used to drive the spindle (generally dynamic platform) and machine base (generally static platform), By controlling the length of the rod in the rod system, the platform supported by the bar system can obtain the corresponding freedom movement, and can realize multi coordinate linkage NC machining, assembly and measurement functions, and can meet the processing of complex special parts. It has the advantages of high modularization, light weight and fast speed of modern robot. Parallel machine tool, as a new type of processing equipment, has become an important research direction of machine tool technology. It has been paid great attention by the international machine tool industry. It is considered as "the most significant progress in the machine tool industry since the invention of numerical control technology" and "the new algebraic control processing equipment in the 21st century".

   

  1. Extreme (large and miniaturized)

  The development of national defense, aviation and aerospace industry and the large-scale of energy and other basic industrial equipment need the support of large and good performance CNC machine tools. Ultra precision machining technology and micro nano technology are strategic technologies in the 21st century. New manufacturing technology and equipment which can adapt to micro and nano size and micro nano processing precision are needed. Therefore, the demand of micro machine tools including micro cutting (turning, milling, grinding) machine tools, micro EDM machines, micro laser machining machines and micro press is increasing gradually.

   

  1. Information interaction networking

  For enterprises facing fierce competition, it is very important to make CNC machine tools have two-way and high-speed network communication function to ensure the information flow is smooth and unimpeded among all departments of the workshop. It can not only realize the sharing of network resources, but also realize the remote monitoring, control, training, teaching and management of CNC machine tools, and also realize the digital service of NC equipment (remote diagnosis and maintenance of CNC machine tool faults). For example, Mazak company of Japan launched a new generation of processing center equipped with an external device called e-tower, including computers, mobile phones, external cameras and in-machine cameras, which can realize the functions of voice, graphics, visual and text communication fault alarm display, online help and troubleshooting, and is an independent and self-management manufacturing unit.

   

  1. New functional components

  In order to improve the performance of CNC machine tools, it is necessary to apply new functional parts with high precision and high reliability. The new features with representativeness include:

   

  (1) High frequency spindle: high frequency spindle is the integration of high frequency motor and spindle parts, which has a series of advantages, such as small volume, high speed, stepless speed regulation, etc., and has been widely used in various new CNC machines;

  (2) Linear motor: in recent years, linear motor is widely used. Although its price is higher than that of traditional servo system, the mechanical transmission structure is simplified and the dynamic performance of machine tool can be improved due to the application of key technologies such as load change disturbance, thermal deformation compensation, magnetic isolation and protection. For example, the 1fn1 series three-phase AC permanent magnet synchronous linear motor produced by Siemens has been widely used in high-speed milling machine, machining center, grinder, parallel machine tool, and machine tools with high dynamic performance and high motion precision; Two linear motors are used for the three-way drive of xhc horizontal machining center of ex-cell-o company in Germany;

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

   

  1. High reliability

  Compared with traditional machine tools, CNC machine tools have increased numerical control system and corresponding monitoring devices, and a large number of electrical, hydraulic and mechanical and electrical devices are applied, which easily leads to the increase of probability of failure; The fluctuation and interference of voltage in industrial power grid are very unfavorable to the reliability of CNC machine tools. The parts of NC machine tools are complex and the machining period is long, and the average time without failure is more than 20000 hours. In order to ensure the high reliability of CNC machine tools, we must design the system carefully, strictly manufacture and define the reliability objectives, and analyze the failure mode through maintenance and find out the weak links. The average time of failure free of CNC system in foreign countries is more than 70000 hours, the average time of failure free of domestic CNC system is only about 10000 hours, and the average time of failure free operation of foreign CNC system is over 800 hours, while the highest time in China is only 300 hours.

   

  1. Green processing process

  With the increasingly strict environmental and resource constraints, the green manufacturing and processing is becoming more and more important, and the resource and environment problems in China are particularly prominent. Therefore, in recent years, the machine tools which do not use or use less coolant, realize dry cutting and semi dry cutting energy saving and environmental protection have been emerging, and are developing continuously. In the 21st century, the trend of green manufacturing will accelerate the development of various energy-saving and environmental protection machines, and occupy more world markets.

   

  1. Application of multimedia technology

  Multimedia technology integrates computer, audio-visual and communication technology, which makes the computer have the ability to process sound, text, image and video information comprehensively. Therefore, it also puts forward the requirement of graphical user interface. The reasonable user interface of humanity greatly facilitates the use of non professional users. People can operate through windows and menus, which is convenient for blueprint programming and rapid programming, 3D color 3D dynamic graphics display, graphic simulation, graphic dynamic tracking and simulation, different views and local display scale functions. Besides, multimedia technology can be used in the field of numerical control technology to achieve the information processing synthesis and intelligence, and it is applied to the fault diagnosis and production process parameter monitoring of real-time monitoring system and production field equipment, so it has great application value.

   

  The domestic CNC machine tools lack core technology, from high-performance CNC system to key functional parts are basically imported. Even though some domestic manufacturers have hard to create their own brands in recent years, the reliability of their products' functions and performance is still far from that of foreign products. In recent years, domestic CNC machine tool manufacturers have acquired some advanced numerical control technologies through technology introduction, merger and reorganization at home and abroad, and foreign procurement. However, there is no research on basic technology such as machine tool structure and precision, reliability and humanization design, neglecting the cultivation of independent development capability, and there is still a big gap between the technical level, performance and quality of domestic CNC machining tools and foreign countries, It is also difficult to get the approval of most users.

   

  Some domestic CNC machine tool manufacturers do not pay attention to the improvement of the overall technology and manufacturing level. The processing means are mainly ordinary machine tools and low efficiency tools. Assembly and debugging are completely manual, and 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 account management method, and the low technology level and management efficiency make the enterprise unable to form enough production scale. If foreign machine tool manufacturers can assemble and transfer out products every week, the domestic production cycle is too long and difficult to control. Therefore, we should pay attention to the improvement of our own technological transformation and management level while introducing technology.

   

  Because of the rapid development of CNC machine tool industry, some enterprises do not pay attention to improving their comprehensive service level, even lack of real understanding of service, only focus on marketing and not pre-sales and after-sales service. Some companies.