Development trend of CNC machine tools in the hott

2022-08-10
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The development trend of CNC machine tools in the era of intelligent manufacturing

CNC machine tools were first born in the United States. In 1948, Parsons company of the United States put forward the assumption of a numerical control machine tool when developing a machine tool for processing the template for helicopter blade contour checking and copying. Later, at the request of the U.S. air force, it cooperated with the Massachusetts Institute of technology to trial produce the world's first three-axis numerical control vertical milling machine in 1952. Its numerical control system adopts electronic tubes

Since 1960, Germany, Japan and Zhonghua have successively developed, produced and used CNC machine tools. In 1968, Zhonghua developed the first CNC machine tool from Beijing first machine tool factory

In 1974, microprocessors were directly used in CNC machine tools, which further promoted the popularization, utilization and rapid growth of CNC machine tools

1 high speed

with the rapid growth of automobile, national defense, aviation, aerospace and other industries and the use of new materials such as aluminum alloy, the requirements for high-speed machining of CNC machine tools are becoming higher and higher

(1) spindle speed: the machine tool adopts an electric spindle (built-in spindle motor), and the maximum speed of the spindle is 200000 R/min

(2) feed rate: at the defense rate of 0.01 μ M, the maximum feed rate reaches 240m/min, and the large-scale surface can be accurately machined

(3) operation speed: the rapid growth of microprocessors provides a guarantee for the growth of CNC systems to high-speed and high-precision targets, opening up CNC systems with CPU growing to 32-bit and 64 bit, and the frequency has increased to hundreds of megahertz and thousands of megahertz. Due to the great improvement of the operation speed, the appropriate defense rate is 0.1 μ m、0.01 μ M, the feed speed as high as 24 ~ 240m/min can still be obtained

(4) tool change speed: at present, the tool exchange time in the advanced foreign processing has been widely controlled within 1s, and the high has reached 0.5s. Chiron company of Germany designs the tool magazine into a basket style, with the spindle as the axis, and the tool is inserted around the circumference. The tool change time from tool to tool is only 0.9s

2 high precision

requirements for the accuracy of CNC machine tools at present, the data on the market tensile strength testing machines some screw rods are T-shaped ordinary screw rods and gapless ball screw rods. Now it is not limited to the static geometric accuracy. The moving accuracy, thermal deformation and vibration monitoring and compensation of machine tools are more and more recognized

in the past 10 years, the machining accuracy of simple CNC machine tools has increased from 10 μ M progress to 5 μ m. In the middle of compact processing, it is from 3 to 5 μ M advances to 1~1.5 μ m. And ultra tight machining precision has formulated a medium and long-term energy technology development strategy to 2020, and Tangshan billet quotation 1460 development plan has begun to enter the nano level (0.001 μ m)。

(1) improve the accuracy of CNC piecemeal control: adopt high-speed interpolation technology, complete continuous feeding in small steps, make the CNC control unit more sophisticated, and adopt high resolution position detection assembly to improve the accuracy of position detection (Japan has developed an exchange servo motor equipped with a 106 pulse/revolution built-in position detector, whose position detection accuracy can reach 0.01 μ M/pulse), position servo system adopts feedforward control and nonlinear control

(2) adopt the technology of error compensation: adopt the technology of reverse clearance compensation, screw pitch error compensation and tool error compensation, and stop comprehensive compensation for the thermal deformation error and spatial error of the equipment. The research results show that the use of comprehensive error compensation technology can increase the processing error by 60% - 80%

(3) take grid check and improve the accuracy of the moving track in the process of processing, and look at the processing accuracy of the machine tool through simulation, so as to ensure the positioning accuracy and repeated positioning accuracy of the machine tool, so that its function is durable and stable, it can complete a variety of processing tasks under the premise of non operation, and ensure the processing quality of parts

the progress of machining accuracy lies not only in the adoption of ball screw pairs, hydrostatic guide rails, linear rotation guide rails, magnetic levitation guide rails and other components, the improvement of CNC piecemeal control accuracy, the use of high resolution position detection assembly, but also in the use of various error compensation techniques, such as screw pitch error compensation, tool error compensation, thermal deformation error compensation, spatial error comprehensive compensation, etc

3-direction flexibility, function compounding and integrated target growth

the meaning of compound machine tool refers to the processing of multiple elements from blank to finished product on one machine tool. According to its layout characteristics, it can be divided into two types: process compound type and process compound type. Process compound machine tools, such as boring milling drilling compound - processing intermediate, turning milling compound - turning intermediate, milling boring drilling vehicle compound - composite processing intermediate, etc; Process compound machine tools, such as compound machine tools for multi face and multi axis linkage machining and double spindle turning center, etc. Adopting compound machine tools to stop processing increases the errors in the auxiliary time and intermediate process of workpiece loading and unloading, changing and adjusting tools, improves the processing accuracy of parts, prolongs the product manufacturing cycle, improves the production efficiency and the manufacturer's market response, and forms parts with high dimensional accuracy, which has a comparative advantage over the traditional production method of process separation

the compounding of machining process also leads to the modular and multi axial growth of machine tools. The latest Turning Center launched by German index company is a modular layout, which can complete turning, milling, drilling, gear hobbing, grinding, laser heat treatment and other processes, and complete the full processing of huge parts. With the continuous progress of modern machining requirements, a large number of multi axis CNC machine tools are increasingly welcomed by major enterprises. At the 2005 China International Machine Tool Expo (CIMT2005), domestic and foreign manufacturers exhibited multi axis machining machines (including double spindle, double tool rest, 9-axis control, etc.) and five axis high-speed gantry machining centers and five axis high-speed milling centers that can complete 4-5 axis linkage

while improving the flexibility of single machine, CNC machine tools are growing towards the goal of unit flexibility and fragmentation. For example, CNC multi axis machining center, tool changing and box changing machining center and other flexible and efficient processing equipment are presented; It presents flexible manufacturing cell (FMC), flexible manufacturing system (FMS), and flexible manufacturing line (FML), which are the bottom processing equipment composed of multiple NC machine tools

on modern CNC machine tools, active tool change assembly and self opening task table exchange assembly have become the basic assembly. With the growth of CNC machine tools towards the goal of flexible targets, function integration is more manifested in: active loading and unloading of workpieces, active positioning of workpieces, active tool setting of cutters, active measurement and compensation of workpieces, "all-round processing" integrating drilling, turning, boring, milling and grinding, and "complete processing" integrating loading, unloading, processing and measurement

4 control intelligence

with the growth of artificial intelligence, in order to meet the growth needs of manufacturing flexibility and manufacturing initiative, the intelligence of CNC machine tools is constantly improving. It is detailed in the following aspects:

(1) adaptive control technology in the machining process: by monitoring the cutting force, the power, current, voltage and other information of the spindle and feed motor in the machining process, manipulate the traditional or modern algorithm to stop identification, so as to identify the force, wear, damage and stability of the tool processing, Adjust the processing parameters (spindle speed, feed speed) and processing instructions in time according to these conditions, so as to make the equipment in the best operating condition, so as to improve the processing accuracy, reduce the rough machining and improve the safety of equipment operation

(2) intelligent optimization and selection of processing parameters: use the experience of process experts or technicians, the general and special rules of parts processing, and use modern intelligent methods to manipulate the mechanism based on expert piecemeal or model-based "intelligent optimization and selector of processing parameters" to obtain optimized processing parameters, so as to achieve the goal of improving programming effectiveness and processing technology and extending the time of production preparation

(3) intelligent fault self diagnosis and self repair technology: according to the existing fault information, use modern intelligent methods to complete the rapid and accurate positioning of faults

(4) intelligent fault playback and fault simulation technology: it can completely record all kinds of fragmentary information, stop playback and Simulation of various defects and accidents caused by CNC machine tools, so as to confirm the notices caused by defects, find out the way to deal with results, and accumulate production experience

(5) intelligent exchange servo drive assembly: intelligent servo parts that can actively identify loads and actively adjust parameters, including intelligent spindle exchange drive assembly and intelligent feed servo assembly. This kind of drive assembly can actively identify the moment of inertia of the motor and load, and actively optimize and adjust the control parameters to make the drive system run best

(6) intelligent 4m CNC system: in the manufacturing process, the integration of processing and testing is an effective way to complete rapid manufacturing, rapid detection and rapid care. The four (i.e. 4m) of measurement, modeling, manufacturing and mechanical operation (i.e. 4m) are smoothly understood in one system, complete information sharing and promote the integration of measurement, modeling, processing, clamping and operation

5 piecemeal openness

(1) open to future technology: because the software and hardware interfaces comply with recognized standards and negotiations, with only a small amount of redesign and adjustment, the new generation of general software and hardware capital can be adopted, accepted and compatible by the existing piecemeal, which means that the development cost of piecemeal will be greatly reduced, and the piecemeal function and reliability will be continuously improved and put into a long life cycle

(2) open to special requirements of users: update products, expand functions, and supply various combinations of hardware and software products to meet special utilization requirements

(3) establishment of numerical control standard: a new CNC fragmentary standard iso14649 (STEP-NC) is being discussed and formulated internationally to provide a neutral mechanism that does not rely on a system and can describe the same data model in the whole life cycle of products, so as to complete the standardization of product information in all manufacturing processes and even in all industrial categories. Standardized programming language not only facilitates the use of users, but also reduces the rest consumption directly related to the effectiveness of operation

6 drive parallelization

the parallel kinematic machine tool overcomes the shortcomings of the traditional machine tool serial mechanism, such as large mass of moving parts, low fragmentary stiffness, the tool can only feed along the solid guide rail, low degree of freedom of operation, insufficient flexibility and agility of equipment processing, and adopts the multi rod parallel connection mechanism between the main shaft (usually the moving platform) and the base (usually the static platform) of the machine tool, By controlling the length of the rod in the rod system, the platform supported by the rod system can obtain the activity of taking care of the degree of freedom, and can complete multiple functions of multi coordinate linkage NC machining, assembly and measurement, which can better meet the processing of large special parts. It 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 a primary research target of machine tool technology in the future. It has been highly regarded by the international machine tool industry as "the most meaningful progress in the machine tool industry since the discovery of CNC technology" and "the new generation of CNC processing equipment in the 21st century"

7 extreme (large-scale and miniaturization)

national defense, aviation and aerospace

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