Research on network communication and control tech

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Research on network communication and control technology of economical CNC machine tools in recent years, with the rapid development and wide application of information technology represented by computer and network communication, great changes have taken place in both concept and technology in the manufacturing industry. The traditional mass manufacturing production mode with relatively fixed machines and production sites as the center and management control from top to bottom is gradually changing to the advanced manufacturing production mode based on people-centered and technology. The idea of global manufacturing is to use the resources (equipment, knowledge, manpower) in different places to manufacture the products required by the market, so the remote monitoring technology of processing unit has become an important part of it. To realize the remote monitoring of machining units, the primary problem to be solved is the network communication and control technology of CNC machine tools

this project is to solve the network communication and control technology problems of traditional economic NC machine tools, and realize the centralized management and network communication of the central server of NC program through the network. So as to adapt to the development of modern advanced manufacturing technology

1. Demand analysis

1.1 problems existing in traditional economic CNC machine tools

traditional economic CNC processing equipment are mainly classified by CNC system: FANUC System (including 3T, 7m, hc-6, 6MB, etc.), AB company system, domestic 3B wire cutting system, etc.: according to the type of digital control program input/output communication interface, there are three types: one is only rs232/rs422 serial port, and the other is only 8/5 unit parallel port of paper tape reader, The three types include the first two types of interfaces at the same time. These three types of machine tools also have the same problem: the memory capacity is small, which is not suitable for the processing of complex, large-scale, high-precision and long program parts; their external interface ability is poor, they have no DNC function, and they cannot realize processing and network control

1.2 the desired solution

is to improve the application environment of NC machining technology on the premise of meeting the most basic application needs and leaving a certain potential for scalability and performance improvement. The following solutions are proposed: machine tool communication connection 5 The intelligent microcomputer can correct the deviation of temperature measurement value Hardware transformation of the port, design corresponding communication interface boards for various machine tools: development of communication control software to realize the single machine communication function of each machine tool: development of other auxiliary functions (such as extraction of processing information in NC program, graphic simulation of NC program, processing of long program, etc.), make up for and enhance the functions of the original NC system from the government level: selection of network system, definition of communication protocol and development of network system control software, Realize the centralized management and network communication of the central server of the NC program

2. System structure

2.1 network system composition and function

the whole network system is composed of central server, network interface, bidirectional data converter, field server, 1-point N-port parallel data transceiver, data receiver and economic NC machine tool

the central server is the central part of the whole network, which mainly completes the overall control of servers at all levels. It adopts the background interrupt working mode, without human intervention, and its foreground can also carry out other work

the field server is the client, which not only serves as the function of the NC server, but also has a powerful network communication function. It accepts various tasks assigned by the central server: obtain the data information of the NC machining program transmitted by the central server from the network, and transmit these data information to the NC File Library: feed back the processed NC program to the central server. It can extract the corresponding NC code from the NC file library of the system, extract the processing part data and information about the raw materials from renewable biological materials such as crop straw, process them, and realize the graphic simulation of NC program. In addition, for the processing of parts requiring long programs, the on-site server also completes the processing task of long programs

the on-site server can serve multiple numerical control devices at the same time. According to the needs, set network nodes in a certain space of the workshop (such as a small workshop, a small local area), place a PC as the on-site server, and select a 1-point N-port parallel data transceiver to serve multiple numerical control devices according to the actual needs

2.2 selection of system network architecture and communication protocol

all kinds of information in the system is transmitted through the network. In the development of computer network, the network systems that have great influence are mainly OSI 7, which enables the experimental machine to give full play to its maximum working efficiency layer reference model and tcp/ip architecture model. OSI reference model is iso7498 international standard. Tcp/ip architecture is the architecture used by the current popular Internet network. Although it is not an international standard, it plays a very important role in the computer network architecture. This is because although the OSI architecture is relatively complete in theory and its layer protocols are well considered, in fact, commercial products that fully comply with OSI layer protocols rarely enter the market and are far from meeting the needs of various users. However, products using tcp/ip protocol have poured into the market. Almost all workstations are equipped with tcp/ip protocol, which has become the de facto standard of computer networks, commonly known as "industrial standard". Therefore, in the network communication system of CNC machine tools, we adopt the network architecture of tcp/ip, which divides the computer network into four layers, namely, application layer, transmission layer, network layer and network interface layer

tcp/ip architecture establishes two protocols for the transport layer, namely, transmission control protocol (TCP) and user packet protocol (UDP). UDP provides users with a datagram protocol without process connection. Data packets are transmitted in the form of independent packets, and the service does not provide error free guarantee. Data can be lost, repeated or out of order: the length of data packets is also limited by the maximum length of one-time processing (the default value is 8192 bytes, and the maximum value is 32768 bytes), No packet splitting and reassembly: TCP protocol is a reliable connection oriented protocol with full duplex byte stream. Compared with UDP, TCP has reliable transmission, no error and duplication of data, and can be received in the order of sending. The data is byte stream

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