Abstract: This paper briefly introduces the current status and basic functional requirements of the domestic CNC machine tool network DNC, and makes some prospects for its development direction. I. Overview With the development of computer technology, the technology of using the PRP (paper tape reading punching machine) and the CNC system for NC program input/output has been in shortcomings due to the preservation, management, capacity, reliability, etc. of the paper tape. Gradually eliminated. Many CNC system manufacturers currently offer computer NC program service functions, but they are limited to their own CNC systems and are not common to each other. At the same time, with the development of market economy and enterprise informationization, the number of CNC machine tools is increasing, and the traditional single-machine management mode can not adapt to the development of enterprises due to backward technical means, low production efficiency and high management and maintenance costs. The need, coupled with the use of a variety of information management systems, such as ERP, PDM, CRM, CAD / CAPP / CAM, etc., must also consider information sharing between various systems to avoid informational silos, therefore, the use of integration It is imperative that the DNC technology manages the numerical control equipment group. Second, several modes of CNC machine tool network DNC At present, CNC machine tool network DNC generally adopts three kinds of network interfaces, namely: based on serial communication RS-232C mode, Ethernet network mode and field bus mode, the following is a brief description. At present, there are two types (including three types of structures) in the DNC market through RS-232C port communication products, namely, the machine operation box and the machine operation box. The structures are as follows: (1) With machine tool box mode, as shown in Figure 1: This type of connection was the model that emerged in the mid-1990s. At the time when everyone used to use single-machine transmission, this method was an innovation. It can be said that it represented the highest level of DNC products in China at that time. The MOXA C320Turbo card (or other multi-channel serial communication card) is connected to the computer via an ISA (or PCI) card, and then connected to the communication module via a shielded 10-core cable. Each communication module has 8 The communication port can be cascaded with multiple communication modules, up to eight, and each computer can be extended by four ISA (or PCI) cards, so that one computer can expand up to 256 RS-232 ports. The distance between the communication module and the computer should not be too long, generally about ten meters. The uploading and downloading of the program is realized by operating the machine operation box (of course, the CNC side also carries out related uploading and downloading operations). (2) New operation box mode with machine tool, as shown in Figure 2: Note that one of the biggest differences between this figure and the previous figure is that MOXA's multi-port serial server becomes CN2516 (or other multi-port serial server), which is a node on a local area network, and is connected to NC through HUB or switch. The program management computer is connected so that it can be placed in any fixed position on the workshop, which greatly reduces the wiring between the workshop and the computer room. Only one network cable is needed. In addition, the CN2516 can be installed on multiple computers. Its driver, multiple computers monitor and control at the same time, bringing convenience to the user's maintenance work. (3) Modern mode (without machine operation box), as shown in Figure 3: This type is changed on the basis of the previous type. It removes the machine operation box, the connection is simpler, the other communication functions are exactly the same, and even can be made stronger and more convenient. Most of the products offered by DNC vendors on the market today are based on this model. Since the machine operation box is removed, the communication information such as the file name of the program sending and receiving program needs to be sent by the CNC. The general practice is to compile a special program on the CNC (this program is not really executed, so it is not necessary Pay attention to whether it conforms to the grammar rules), which contains some feature strings to express the sender or receiver, such as: (B) Program Send When the program is sent, you only need to add the character string to the original program, which means the name of the file you want to save on your computer. E.g: 2. Fieldbus mode Although the most widely used in the CNC workshop DNC system is the RS-232 serial communication interface, when there are many CNC devices connected to the DNC host, there are many problems of complicated connection and complicated communication, and the reliability of the serial interface is poor. Low speed, based on these issues, forcing people to seek better solutions. Field Bus is a system that implements bidirectional serial multi-node digital communication between industrialized devices and computerized control devices. It is a new technology that flourished in the international 1990s. Its application forms a new network integrated distributed control system. It meets the needs of both process control automation and manufacturing automation. Since the fieldbus is based on digital communication, multivariable two-way communication is possible between the field and the control room. In order to solve the problems of high-speed data transmission, real-time performance, and communication distance, it is necessary to develop high-speed data communication technology and use Fieldbus. The integrated system for the next decade will be the Field Bus era. The fieldbus adopts a three-layer network structure—the physical layer, the data link layer, and the application layer. The architecture is shown in Figure 4. At present, there are many kinds of fieldbuses, and many applications include CAN (Controller Area Network), LON (Local Operating Network), and Profibus. In the following, the application of fieldbus in DNC is only described by CAN bus. Figure 4 Fieldbus architecture As the network system for industrial field control, reliability and real-time performance are the most important requirements. The CAN bus has many unique features in this respect: Firstly, in order to meet the reliability requirements, the CAN bus adopts cyclic redundancy code verification and frame detection. , confirm signal error detection, bus monitoring, bit filling and other error detection and error correction measures, thus achieving high reliability, the average bit error rate is less than 10-13; Second, CAN uses a unique bit arbitration technology, Compared with CSMA/CD network (IEEE802.3) and Token Ring (IEEEE802.4), it has higher real-time performance; in addition, CAN bus transmission rate can reach 1Mbps, long-distance transmission can reach 10km, interface is simple, installation is convenient, system cost low. The transmission medium can be twisted pair, coaxial cable or optical fiber. The topology of the CAN bus is shown in Figure 5. Figure 5 CAN bus topology 3. LAN mode With the rapid development of computer application technology and network technology, the function of the numerical control system has also been greatly improved. Thus, in recent years, a new type of CNC machine tool network DNC has appeared in the field of DNC-- - Ethernet based DNC. Due to the continuous development of technology, the continuous deepening of the concept of network and openness, the openness of technology has been unanimously recognized by all. The world's leading CNC system manufacturers have invested in the development of DNC communication interface, providing DNC network interface options and communication in line with MAP standards. Software, such as FANUC's 0I (MB) and above CNC systems have DNC network interface options, and provide a development interface library, third-party developers can carry out secondary development on this basis, which can form a powerful real DNC can provide comprehensive control of CNC machine tools. The use of LAN communication method has greatly improved the efficiency of NC program management. At the same time, the LAN mode for network communication through TCP/IP communication protocol is about to become a popular method. The system connection is as shown below: Figure 6 LAN Fieldbus mode and LAN mode can connect a variety of field devices over long distances, but fieldbus must have its own dedicated protocol, must use the corresponding development tools and development platform, the price is relatively expensive, and it is difficult to achieve between different manufacturers and different devices. Interoperability. Third, CNC machine tool network DNC basic functions In fact, what network structure is used by the CNC machine tool network DNC is not the most important. The key is what kind of service the DNC system can provide to users, and how much benefit users can get from it. From the definition of DNC itself, its role in the production site is also constantly evolving. From the “direct digital control†of equipment to “distributed digital controlâ€, the basic functions of DNC are summarized as follows: 2. control function: History: Alarm history, operation history CNC remote control display various machine parameters Set various machine parameters Display NC program various information: such as memory size, number of programs, etc. Select NC program: select current machining program, find any NC program editing NC program: Edit the NC program in the CNC system Delete the NC program: directly delete the NC program in the CNC system Clear the alarm history Clear the operation history System reset: Remote start by remote CNC: Remote pause by remote start processing: Remote pause processing Fourth, CNC machine tool network DNC development direction CNC machine tool DNC network technology will be based on a single technology, the application of computer network communication technology, to achieve a high degree of information integration, and to the direction of CIMS. The main points of future development of the DNC network are as follows: 1) New network communication technology: As discussed above, there are two new types of network communication technologies, namely Ethernet and fieldbus. For CNC system manufacturers, the development of open systems, that is, the integration of PC microcomputer technology into CNC In the system, the application interface MS-WINDOWS is used, making full use of the huge software resources of the PC microcomputer mainstream operating system MS-WINDOWS, making the CNC system network communication more convenient. More and more CNC manufacturers are now providing Ethernet interfaces and fieldbus interfaces for their CNCs. Open CNC systems come in two ways: 2) Wireless communication technology: wireless communication technology is adopted to realize wireless communication between computer and CNC machine tool to reduce on-site construction and shorten the construction period. The wireless modem technical indicators are as follows: 3) High integration of information: V. Summary The several DNC models introduced above have been extensively experimented and developed by the author in the past decade, and some models have formed mature products. If there is any inconvenience in the above content, please criticize and correct. In short, in China, CNC machine tool network DNC has experienced a difficult and tortuous development path after more than ten years of development. Nowadays, it has made great progress in the era of high-tech development. However, in addition to RS-232C serial communication based on serial communication. In the mode, there are a few limited excellent DNC ​​products. In the local area network and fieldbus mode, only some limited discussions have been made. No mature products have yet appeared, and it is necessary for the majority of colleagues to continue to work hard for China's manufacturing industry. Bigger contribution! I sincerely hope that the flower of the CNC machine tool network DNC will be splendidly opened in the vast manufacturing market! Paper.Mica.Nomex wrapped aluminum(copper) wire Paper Coverd Aluminum Round Wire,Kraft Paper Wrapped Wire,Paper Coated Flat Aluminium Wire Ouwei Electric Co., Ltd , http://www.libo-metal.com
At present, the majority of CNC machine tool users have reached a consensus on the implementation of the CNC machine tool network DNC management, but in the actual implementation process should be done to what extent, what effect is still unclear, in the current domestic CNC machine tool network DNC field still exists Some fish are in the process of mixing beads, and DNC is in a stage of rapid development. Various new network structures and high-tech are emerging, which makes it easier for the majority of CNC machine users to dazzle. This article attempts to make a concise introduction here.
1. Serial communication RS-232C mode 
Figure 1 DNC network structure diagram form one 
Figure 2 DNC network structure diagram 2 
Figure 3 DNC network structure diagram form three
(A) Program request %
O1000
(/GETXXXX) (where XXXX represents the name of the file that needs to be requested for download)
M30
%
After the file is compiled, the file is sent to the computer. After the computer receives the file, it analyzes it. If it requests the file download command, it generates a program download queue, and waits for the machine to send the start and send the command. Downstream.
%
O1000
(/NAME XXXX) (XXXX represents the name of the file you want to save on your computer)
...
M30
%
After the current file is uploaded to the computer, if the computer analyzes the feature character /NAME (the type of the feature character should be determined according to the special requirements of the system, which is only indicated here), the current file is saved to the string represented by it. In the file, if the feature character is not found, it is saved to "O1000.NC" (that is, the program number is preceded by the letter O). 
DNC system structure diagram
1. Communication function:
Two-way transmission of NC program: All CNC equipment implements centralized management of the network, and uses the network to carry out bidirectional transmission of NC programs (including machine parameters, tool offset files, macro programs, etc.), thereby realizing mass storage and integrated management of NC programs.
Client/server structure: Each CNC machine tool is defined as a client device, which utilizes the communication port of the CNC system (such as RS-232, Ethernet network, field bus, etc.) and communication functions. The operator can perform data on the CNC machine tool. Two-way transmission and access to all operations of managing server-side data, the server side automatically handles the operation request of the CNC side without human intervention.
Group control and distance: a single computer management CNC machine group; communication distance can reach several kilometers.
Concurrent operation of the DNC network: Ensure that all incoming CNC devices can perform concurrent communication transmissions at the same time.
DNC online processing: DNC online processing in full client mode ensures that functions such as breakpoint resuming and subroutine call can be realized by the operator on the CNC side.
Interactive event response mechanism: Every operation of the CNC side should have message feedback, that is, the operator can get the prompt information file on the numerical control device side regardless of whether the operation is correct.
Data sharing: Allows the operator to access other CNC equipment or virtual machine information on the local CNC equipment to facilitate the transfer of parts.
Support for long file names: NC program names implement long file name management on the WINDOWS platform and automatically convert program numbers with program numbers.
Communication log: records all communication processes of the workers and classifies the recorded information.
Information collection: Real-time acquisition of machine tool processing information through the macro program variable output function of the machine tool, and real-time summary of machine tool use efficiency, part processing time, tool life and other information.
Network communication platform: use DNC communication network to send processing tasks, tool information, process information and processing results report, etc., in order to achieve the initial integration of production information.
In the normal RS-232C serial communication port network mode, DNC can not achieve real-time control of CNC machine tools. Generally, only Ethernet-type DNC or fieldbus-type DNC can achieve this purpose. The function is as follows:
CNC network setting Set the IP address and port address of the networked CNC. CNC status monitoring processing status: processing, idle, alarm, fault information networking status: online, offline position information: absolute position, relative position, mechanical position, remaining movement, Feed rate
PC-CNC: Fusion of CNC functions based on PC microcomputer.
CNC-PC: The function of the PC microcomputer is integrated in the CNC system.
With RS-232C interface 2.4GHZ, no frequency application is required.
High speed (119Kbps), high reliability.
The effective communication distance is 100 to 200 m.
Collect more complete machine information and provide first-hand information for workshop production management.
Intelligent analysis of collected information.
Real-time control of the device.
It is truly seamless with systems such as ERP, PDM, and MES.