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CNC manufacturing systems commonly used in network communication interface mode DNC

In Electronic Infomation Category: C | on February 09,2012

Abstract: CNC manufacturing systems in the network commonly used in server-based serial communication interface DNC mode, each of the integrated analysis of the meaning of DNC system and LT1251CS datasheet and characteristics of the interface model is proposed based on serial servers, heterogeneous DNC CNC system integration methods, numerical control manufacturing systems discussed in the network serial port server-based integration DNC system development.

DNC distributed digital control (DiSTributed Numerical Control), based on computer technology, communication technology, numerical control technology, based on the upper control computer numerical control machine tools and LT1251CS price and integrate, in order to achieve the concentration of CNC machine tools control, management, and LT1251CS suppliers and CNC machine tools and the upper control the exchange of information between computers. It is a modern mechanical processing enterprises equipment integration, information integration, functional integration of a new method of manufacturing automation is an important model for achieving CIMS integrated manufacturing systems and other important components.

in the past 10 years, people will be a lot of energy to invest in FMS (Flexible ManufactureSystem) systematic study, but the actual application results show that, FMS this not only focus on the integration of information flow, more emphasis on logistics integration and automation, while having high efficiency and high degree of automation, but the investment risks, slow, less reliable. Relative to the FMS, DNC is a small investment, quick, flexible and has better integrated manufacturing system. With computer technology, digital technology and network communication technology, DNC meaning and function are expanding, the current DNC ??system already has manufacturing data transfer, status of data acquisition and processing, tool management, production scheduling and control, unit control and CAD / CAPP / CAM interface and other functions.

in the analysis of existing DNC host communication interface with the CNC system based on features, from the perspective of DNC communication interface function can be divided into basic DNC DNC, the narrow and broad DNC DNC three. Table 1 shows the basic content.

Table 1 DNC Classification

present, the actual DNC system integration applications, often based on the serial port communication interface mode, Ethernet mode. I focus on these two kinds of DNC communication interface modes were introduced.

1 DNC-based serial port communication interface mode

use of CNC machine tools supplied RS232C or RS485 interface, with point-type or star topology, serial communication. This is the most widely used in the workshop in a method of communication, but this method of communication there are many industrial computer, high input costs, administration and maintenance workload and error-prone and other shortcomings. Most digital systems currently in use with a RS232C serial communication interface. The RS232C interface can be directly used for basic communication and narrow DNC DNC communications.

1.1 serial expansion card with the DNC communication interface mode

with a serial port expansion card DNC interface model is the mid-1990s model, shown in Figure 1, we also commonly used at that time the era of stand-alone transmission, this approach is a innovation can say that it represents the product at the highest level of Chinas DNC. MOXA C320Turbo card (or other multi-channel serial communications card) is ISA (or PCI) card connected to your computer the way, and then through a 10-pin shielded cable to connect the communication module, communication module with eight each communication port, multiple communication modules can be cascaded, each communication port with up to 8 nodes, each computer can also extend four ISA (or PCI) card so that a computer can be extended up to 256 RS-232 interface. The distance between the communication module and the computer can not be too long, usually about ten meters.

1.2 DNC communications with the servers serial interface mode

serial servers function is from the TCP / IP protocol packets, parse the serial data stream; the other hand, the serial data stream can also be labeled as TCP / IP protocol packets in order to achieve data network, it can connect multiple serial devices and serial data stream can be selected and processed, the existing data into the RS232 interface port for IP data, so it can send serial data to the traditional Popular IP channel, without the premature elimination of the original Ethernet module without CNC equipment to improve utilization of existing equipment, saving investments, simplifies wiring, as shown in Figure 2. In data processing, is a serial server to complete the RS232 link and connection-oriented Ethernet connection for communication between non-data storage control system from the serial device serial data stream processing, and the format conversion, making the spread in the Ethernet data frame, the Ethernet data frames from the judge, and converted into serial data served to respond to the serial device. In practical applications, the serial port server with TCP / IP protocol Ethernet interface mapping for the Windows operating system, a standard serial port, as for ordinary applications can be send and receive the same serial port and control, therefore, serial servers in NC networking function of the system is to any of the information from the CNC system transparently transferred to any computer on the LAN, you can put any information from the LAN transparently transmitted to the CNC equipment; equivalent to the network LAN and serial devices by one IP address for the serial server is configured so that CNC machine tools to become a node in the LAN, which LAN has some of the features, sharing of resources.

such as MOXA CN2516 multi-channel serial servers, local area network when it can be a node on the network through the HUB or switch to a computer connected with the NC program management, so that it can be placed in the workshop any fixed position, greatly reducing the floor to the management center of the wiring department, in addition, CN2516 can also be installed on multiple computers in their drivers, multiple computers can simultaneously monitor and control, maintenance work to the users convenience , the network structure shown in Figure 3.

Figure 3 with the serial server generalized DNC network structure

serial server and the value of the real advantages of the embodiment is not reflected in the way of direct application on the device connected to the Ethernet it important objective, numerical control equipment through the serial port to connect to server Ethernet, the wiring is very simple, only need to connect to the serial server to the hub or switch, serial port by setting the servers IP address, you can make the Ethernet port on the server as a node, so that the connection to the serial port server connected to the Ethernet CNC system, through the networking can be a different numerical system, different types of serial ports (such as RS232, RS422 and RS485), connect to the Ethernet, NC heterogeneous systems network. The networking of the entire enterprise can be connected to the network NC system, the networking process, in addition to expanding the use of switches and hubs, but also can take advantage of industrial Ethernet switches, such as MOXA EDS508, different models can be extended serial servers, NC equipment, flexible networking, sharing of network resources to achieve all the numerical control system and centralized management, control, manufacturing technology to build a platform for the network, the network structure shown in Figure 4.

Figure 4 with serial port server Ethernet DNC ??general structure

2 Ethernet-based serial port servers DNC mode

With the rapid development of industrial Ethernet, industrial automation, unified communications network is gradually to the industrial Ethernet, and is gradually extended downward. Based on Industrial Ethernet and TCP / IP technology in the application of DNC communication system has become the new direction of research DNC, from the original 10Mbps Ethernet speeds up to 100Mbps and even to todays 1000Mbps, enough bandwidth and switching set line device applications to solve the problem of uncertainty of Ethernet, the Ethernet has the ability to meet the requirements of real-time systems, and secondly, the Ethernet switch to connect its ports on each network node provides a separate bandwidth, connection different in the same switch device does not exist above the competition for resources, which is equivalent to an exclusive segment of each device; again, full-duplex communications technology and equipment and switches for each port provided between the sending and receiving a dedicated channel, Thus the conflict between different Ethernet devices greatly reduce or completely avoided. Therefore, more and more Ethernet-based industrial communication network can be applied in the DNC system.

with Ethernet interface for some advanced CNC machining centers, equipment and computer equipment, can be directly connected to the switch; for only with RS232 or RS485 serial interface such as CNC equipment, through the serial port server (such as MOXA Nport5210) into the Ethernet port, then connect to the switch. DNC server through an Ethernet switch and the bottom of the CNC equipment to achieve information exchange, enabling the server to the CNC control and management of networking equipment, shown in Figure 5.

Figure 5 Ethernet based DNC mode structure

Ethernet based DNC system to make the workshop as well as enterprise-wide information network and DNC communications network to the overall integration, and CNC machine tools can directly access the Internet, remote information transmission, adapted to the the needs of modern manufacturing network while accessing the Internet through business alliances the Internet, each server in the corporate alliance between the data and information flow. Enterprise server interface through the DNC system, external provision of services and resource sharing. In order to prevent inter-corporate alliances on the Internets information flow and collaborative activities emerging network security risks. VPN technology can be used in a business alliance established between a virtual private network.

VPN with a high degree of network security, easy to extend and adaptable, business-to have full control over the network, you can always connect with the outside world. Therefore, the use of VPN technology to create business alliances workshop integrate DNC system through a VPN to achieve the alliance between the network design, manufacturing, is currently under networked manufacturing environment, a viable and safe manufacturing model.

3 Conclusion

information technology and the rapid development of computer network technology to the manufacturing industry had a tremendous impact. In todays era of economic globalization, in order to respond quickly to market demand, improve product R & D capabilities, shorten product development cycles, reduce development costs and improve the competitiveness of enterprises, manufacturing enterprises must enter the network from the traditional manufacturing model of production mode. Network as an advanced manufacturing mode manufacturing model, providing manufacturing companies in the network environment, from product design to manufacturing and finally to business management and marketing specific implementation technology. In the networked manufacturing mode, DNC systems of modern machinery manufacturing enterprises as an advanced mode of operation, its functions include not only the shop floor manufacturing equipment, communications and centralized control and management, but also extended upward to the companys other departments, as well as manufacturing alliances and cooperation communication of information between the corporate sector integration. Through the DNC system and network technology enables dynamic alliance between the reallocation of resources and restructuring, and new product co-design and remote manufacturing and processing.

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