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Application of PLC in packaging machinery Abstract: Taking Siemens s7-cpu313c PLC as an example, this paper introduces a typical industrial control system in detail. The system is compact, mature and practical, and has strong expansion performance. It can be used in a variety of industrial control systems. Abstract：This article makes the usage of the SIEMENS S7-CPU313C PLC as a living example, introces one of the typical instrial control system, This control system is full natural , and has a small size, it can be used for many kinds of instry device. Key words: PLC, human machine interface, frequency speed 1、 With the rapid development of microelectronics technology, the control technology is becoming more and more perfect and mature. As the core component of industrial control, PLC has stronger and stronger control function, smaller and smaller volume, and its operation is more and more high-speed and reliable; Human machine interface (HMI) has completely broken the traditional button, signal lamp and other operation modes, making the equipment operation interface more popular, friendly, flexible and diverse. Its powerful storage function and communication ability have brought unimaginable benefits and convenience to the equipment manufacturing and users. It is the general trend to replace the traditional equipment operation interface; At present, the control technology of frequency converter used for ordinary motor speed regulation has far exceeded the single V /F control mode in the early stage, and has developed rapidly in the direction of sensorless vectorization and direct torque control, so that it has been widely used in all walks of life. 2、 Equipment process flow ap-5022 automatic edge sealing and packaging machine is a full-automatic high-speed three edge sealing equipment designed, developed and produced by our company on the basis of introducing and digesting similar foreign equipment. It can be widely used for shrink film packaging of related articles in food, pharmaceutical, health, culture and education and other industries. The motion mechanism of ap-5022 is mainly composed of three parts. The film feeding motor and film collecting motor are used to control the supply of shrinkable film and the recovery of waste film. They are driven by frequency converter and realize stepless speed regulation; The feeding and discharging conveyor belts are driven by a motor respectively, and the feeding and discharging speeds are continuously adjustable between 0-40m /min through variable frequency speed regulation, so as to adapt to various packaging objects; The transverse sealing and cutting motor is used to control the up and down movement of the transverse sealing knife, and the up and down movement of the longitudinal sealing knife is controlled by the cylinder. The analog quantities of ap-5022 automatic edge sealing packaging machine include temperature and speed. The temperature control circuit converts the sealing and cutting temperature signals in the vertical and horizontal directions into 4-20mA signals through the temperature transmitter for PLC sampling; The running speed signal of the conveyor belt set through the man-machine interface is converted into a 0-10V signal through PLC digital operation and D /a conversion, which is sent to the analog input end of the frequency converter to control the running speed of the conveyor belt. 3、 According to the above equipment process flow and considering the expansibility and export requirements of the equipment, it is decided to adopt s7-cpu313c compact PLC and tp170b man-machine interface of Siemens as the core control device of the equipment control system. The specific configuration block diagram is shown in Figure 1. S7-cpu313c in the figure is a compact and cost-effective high-performance CPU module recently launched by Siemens. It has integrated 24di /16Do, 4-channel analog input, 1-channel PT100 thermal resistance input and 2-channel analog output, with fast operation speed; The analog input and output signals can be selected through programming software, and the signal types such as ± 10V, 0-10V, ± 20mA and 0 /4-20mA can be flexibly selected to meet the needs of a variety of applications. In addition, the CPU module supports multiple functional modules of S7-300 series, such as high-speed counting module, positioning module, etc. the system expansion is flexible and convenient. Tp-170b in the figure adopts 32-bit microprocessor and is based on Windows CE operating platform. It runs at high speed and reliably. It supports up to 500 user interfaces, 1000 variables and 100 user formulas, and can store up to 1200 product production data to meet the needs of users for a variety of applications. Multipoint MPI interface is integrated on s7-cpu313c and can communicate with S7-PLC, programmer or human machine interface (HMI) through PROFIBUS connector at the same time. Generally, the transmission rate (default) is 187.5kbps, and the transmission rate of 19.2 Kbps can also be specified. It is a simple and practical communication network with convenient connection, high-speed and reliable communication. 4、 Software control the software design of this machine includes two parts, one is PLC control program, the other is man-machine interface control screen. PLC control program is the core part of local control. Combined with the characteristics of Siemens S7 Series PLC structured programming, the design of PLC program control structure block diagram is shown in Figure 2: the organization module ob1 in the figure is the program block corresponding to the main program of cyclic execution, which is the backbone of step 7 program. Most other OBS correspond to different interrupt handlers. Closely related to each ob is its corresponding type and priority. The priority of ob1 is relatively low. Its priority is 1, so ob1 can always be interrupted by other ob. The control function modules fc1-fc8 execute corresponding control functions and complete the actions of corresponding equipment on the equipment according to the current operation state of the equipment; The control function of the temperature control function modules FC10 and fc11 is to read the current temperature signals in the horizontal and vertical directions of the equipment. After D /a conversion and digital processing, the results are compared with the set temperature. The results of the comparison are used to control the switches of the heaters in the horizontal and vertical directions. The switching frequency and response speed of the heaters can be realized by setting the parameters of the PID regulator. The shared data module db100 is used to store the current operation state and working mode of the equipment, mainly including the setting value and actual value of the sealing and cutting temperature in the horizontal and vertical directions, the setting value of the operation speed of the feed /discharge belt, and the setting value of each timer and counter that need to be adjusted. The stored data can be called by each functional module at any time. 5、 Conclusion at present, ap-5022 automatic edge sealing packaging machine has high speed and reliability, and has been mass produced and exported abroad. The above hardware configuration is mature and efficient, and can be used in a variety of industrial control occasions. References: 1. Siemens SIMATIC STEP7 V5.3 programming, December 2, 2004, Siemens S7-300 /400 ladder logic programming, January 3, 2004, Siemens TP170A /B equipment manual, December 4, 2001, S7-300 /400 PLC application technology, edited by Liao Changchu. I only found one for you in January 2005. I hope it will be helpful to you