Research and Practice of CNC Network System

In recent years, with the unprecedented development speed of the manufacturing industry and a high level of development, China is becoming one of the global manufacturing centers.

Driven by this great situation, the market is increasingly demanding technical talents in manufacturing, especially those mastering modern manufacturing technologies. Jiangxi Industrial Vocational and Technical College actively implements the principle and policy of the country to vigorously develop vocational education. In recent years, it has trained thousands of professional and technical personnel for the country every year. The Department of Mechanical and Electrical Engineering also undertakes the training and education task for nearly 1,000 high-level students every year. .

In response to the rapid increase in the number of professionals majoring in CNC application technology, mold design and manufacturing technology, the College has invested heavily in improving the conditions for running the Department of Mechanical and Electrical Engineering, and established metalworking internships and CNC training workshops and CAD/CAM computer labs. The need for teaching and practice. The teaching reform research team will network the CNC machine tools with the CAD/CAM computer LAN, fully and efficiently realize the potential of the existing equipment, enhance the practical operation ability of the CNC machine tools and the application level of CNC technology and computer network technology.

1 The conditions existing in the network before the network training workshop has vertical CNC milling and boring machine, CNC lathe and CNC wire Cutting Machine more than 10 sets, its CNC system has Japan FANUC system, domestic China medieval star system and Guangzhou CNC system. The software selected by the CAD/CAM laboratory is PTC's Pro / E, CNC's Master CAM, and the CAD / CAM computer forms the local area network.

2 The main problems existing before the network 2. The program transmission efficiency is low, the training effect of the equipment is poor. There are more than ten machine tools in the CNC training workshop. Before the networking, for some CNC machining with less program, the original manual is used. Keyboard input method, the drawbacks of this method are: low efficiency, long machine life and error-prone. The time for students to manually enter the program during the CNC internship can account for more than half of the machine's boot time, which seriously affects the performance of the CNC machine. For some NC machining with large program input, it is one-to-one special plane transmission through RS232 or RS422 interface, that is, using a computer to carry out data transmission on the machine side, the transmission is time-consuming and laborious.

Even if the training workshop implements two shifts every day, the ability to train students is still limited. In the face of the increasing number of students every year, the existing equipment can not meet the demand.

2. 2 equipment investment and maintenance costs high Each CNC machine tool must be equipped with a computer, more than 10 machines must be equipped with more than 10 computers. The disadvantage is that the operating environment is bad, the board of the computer is often burnt out, and the computer is difficult to maintain in the later stage.

2. The gap between the teaching and practice of modern advanced management and manufacturing mode CAD/CAM computer LAN and CNC machine tools do not have any connection. The students who participated in the training completed the programming training of CNC machining in two completely different environments. The effect is not very good. The management of the program files is confusing, and there is a potential danger of burning the serial port device when the transmission cable is frequently plugged and unplugged, and the transmission is limited by the distance.

In summary, each of the drawbacks has seriously affected the efficiency of CNC machining practice, so it is urgent to find an effective way to solve the above problems.

3 Software and hardware management system of CNC teaching system In view of the above problems, after many investigations and studies, it is decided to design a set of CNC teaching network management system that meets the current situation of the college, that is, using LAN management client + network server + machine tool client Networked management system. The LAN CAD/CAM workstation is connected to the network server through the TCP/IP protocol. The CNC machine tool cluster is connected to the multi-port serial card extended by the network server through the RS232 serial port, thereby realizing the information exchange of the entire network. In terms of software, CNC machine tool networking software is used as the network management system software for numerical control teaching. In order to realize the networked management of NC teaching and training, we can get rid of the two different teaching and operating environments of training and experiment.

The NC teaching network management system mainly includes CAD / CAM computer LAN laboratory, CNC network management server and CNC machine tool group. The network management server is a PC computer with dedicated software for network management of the network. The network server uses multiple serial port distributors, communication cables, optical isolators at both ends, communication modules for long-line drivers and related hardware devices and RSs for all networked devices. - 232 communication interface for connection communication. Multiple workstations in the LAN can be installed to manage the client window, access the network server and communicate with all networked CNC devices, thus forming a multi-point, three-dimensional CNC equipment communication management network.

The work of the network management server is to accept the instruction scheduling of the networked CAD / CAM computer workstation (management client) or CNC machine tool (machine client) to realize the unified management of information between the CNC machine tool and the workstation.

CNC machine tool networking system software is divided into 3 layers, its core is the control core, responsible for completing the multi-way implementation scheduling, the second layer is the interpretation driver layer, responsible for completing the interpretation of the CNC description language and driving the communication interface of various types of CNC machine tools, The third layer is the physical interface layer, which is responsible for communication with the communication interfaces of various CNC machine tools. The three layers cooperate with each other, so that the CNC control host can not only connect and simultaneously drive the communication services of multiple and multiple types of CNC machine tools, but also the CNC control host can simultaneously respond to the DNC requests of several different types of CNC machine tools.

4 The main function of the NC teaching network management system After the above-mentioned technical rectification, the NC training workshop proved that the existing CNC teaching network management system has obvious advantages through a period of groping operation and practical operation, which not only improves the numerical control. The equipment utilization of the training workshop, and the expansion of many teaching functions. The specific performance is as follows: (1) For the CNC system with DNC function, multiple machines can be processed simultaneously on the network; (2) Each CNC machine can access or download the NC program under the machine catalog and public directory; 3) completely get rid of the situation of manual input program and single input program, realize long-distance automatic program transmission; (4) easy to operate, without the help of other equipment or programmers, the operator inputs the corresponding instruction on the operation panel of the machine tool, It can upload or download the part processing program; (5) It can transfer the program in parallel, that is, one network management server can simultaneously communicate data to multiple CNC machine tools; (6) High transmission reliability. Use the data verification function of the dedicated software to immediately report an alarm if there is an error. The software also has the function of checking and uploading files. After each file is uploaded, it can return a check file to ensure the security of the data. (7) With the software's transfer log function, you can view the date, time, file name of the data transfer and Upload or download content to record the operator's operation process and error information; (8) automatically convert the program long file name on the CAD / CAM computer workstation (management client) to a CNC machine tool through the web server Program number, automatic conversion of file name and program number, completely changed the limitation of program number on NC program management; (9) The number of CNC machine tools is not limited; (10) Network management server works 24 hours, on the network at any time CNC machine tool implementation management and data communication.

5 After the implementation of the teaching network management system, the efficiency of NC teaching has been greatly improved, and the program transmission and program management have been significantly improved. The phenomenon of queuing and transferring students in the practice workshop has not been eliminated, and the transmission is frequently removed. The cable is plugged and unplugged.

Before the NC teaching network management system was built, the NC program was basically in the primary management state. After the construction, depending on the function of the dedicated network management software, all the programmed programs are placed in the directory corresponding to each machine tool, and each program is named according to the part drawing number, and no duplicate name occurs. The students who participated in the training will soon be able to use the CNC network management system to understand the programs on the network and download them at any time. In the same time, I was able to do more programming training, so that the students' ability of hands-on programming has reached a new level.

Before and after the network comparison, there are obvious changes in the following points: (1) shortening the time of the transmission program, that is, saving the cost of the expensive CNC machine tool. The operator's labor intensity is reduced, and the program transfer can be completed by simply inputting a simple command on the machine panel. Accuracy is high and the part program can be absolutely correct even if it is retransmitted. Easy to modify, if the program used for the first time is modified on the spot, it can be used for the next call after uploading; (2) It can meet the needs of numerical control teaching and fully and effectively exert the effect of existing equipment; (3) Responsibility Clearly, once a problem arises, it is easy to analyze whether it is a programming reason or an operation reason; (4) Management has achieved unified and networked, so that students have initially mastered the modern advanced management and manufacturing model, laying a good foundation for the future.

The system has been running very stable since the project was completed last year. The management system is a network system based on RS-232 serial communication technology. At present, many domestic enterprises use CNC machine tools with ordinary RS-232 or RS-422 serial ports and economical CNC machine tools modified with microcomputers. The application efficiency of modern manufacturing enterprises will be very significant, and it is a practical and feasible technical transformation solution in line with national conditions.

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