Buildings are one of the basic infrastructures and conditions for human life. With the improvement of living standards and the development of human society, people's demand for buildings is becoming increasingly urgent, and the scale and number of construction projects are constantly growing. In my country's construction industry, reinforced concrete structures still account for a considerable proportion. In reinforced concrete structures, steel bars form the skeleton of the entire building, consisting of main steel bars and stirrups. The shape and size of stirrups are related to the design of the main steel bars, and their usage is many times greater than that of the main stirrups. However, in actual stirrup production, stirrup production consists of two parts: a straightening device and a bending device. Current simple stirrup bending equipment is far from meeting the needs of large-scale, multi-variety processing, resulting in high labor intensity for workers, low production efficiency, and high labor costs.
2. Introduction to S7-300 and Hardware/Network Configuration: SIMATIC S7-300 is a modular, small-to-medium-sized PLC system manufactured by Siemens, Germany, which can meet the needs of applications with medium performance requirements. The S7-300 system can be configured into systems with varying requirements through the combination of various individual modules. Its instruction set boasts a high-speed (0.6~0.1μs) operation speed. The S7-300 supports floating-point and inverse trigonometric function operations, enabling efficient and complex arithmetic calculations. The S7-300 allows for convenient and simple configuration and parameter assignment of all modules through the unified Step 7 software. Multi-level password protection effectively safeguards users' technical secrets, preventing unauthorized copying and modification. The S7-300 possesses powerful communication capabilities, offering multiple communication interfaces and connecting to AS-I bus interfaces and industrial Ethernet bus systems via various communication processors. The Multipoint Interface (MPI) is integrated into the CPU for simultaneous connection to programmers, PCs, HMI systems, and other SIMATIC S7/M7/C7 automation control systems. The bending process involves extensive calculations, requiring a PLC with powerful computational capabilities; Siemens' S7-300 perfectly meets our requirements. Siemens' Step 7 Professional V5.4 SP3 programming software supports three programming languages: LAD, STL, and FBD, and also supports mixed programming of these three languages, greatly improving programming efficiency. Therefore, considering the realities of stirrup production and the high dust and electromagnetic interference environment, which exceeds the capabilities of industrial control computers, we chose a solution for designing automated stirrup production equipment. This solution utilizes an advanced and mature S7-300 PLC as the main core, a touchscreen as the human-machine interface (HMI), and a Yaskawa AC servo drive system as the actuator. The control system based on the S7-300 consists of a CPU314C-2DP (CPU), an FM354 (controller for the drive and traction section), an FM353 (controller for the bending section), an SM321 (input module, providing feedback on the correctness of the position of various actuators and control signals), and an SM322 (output module, controlling the operation of various solenoid valves), as shown in the diagram below. For the connection network between the S7-300 and the touchscreen, we choose MPI. The MPI address of the CPU314C-2DP is set to 2, the MPI address of the SM354 is set to 3, the MPI address of the SM353 is set to 4, and the address of the HMI is set to 1. The network configuration is shown in the diagram below. III. Working Principle Based on the actual production conditions of stirrups, we adopt a scheme that combines the straightening device and the stirrup bending forming device. The straightening section mainly consists of two rows of straightening rollers, horizontal and vertical, which remove the bending stress of the rebar through roller compression, as shown in the figure below. For user convenience, the position of the upper straightening rollers can be adjusted to accommodate rebars of different diameters. The straightening device is driven by an 11KW AC servo motor, which simultaneously drives and feeds the rebar. The bending section uses a wraparound bending method, with one axis as the center and another axis arm rotating around this axis, as shown in the figure below. The entire bending section can extend/retract around the rebar during bending, and can also rotate clockwise/counterclockwise. The bending speed and angle are controlled by the positioning module FM353, achieving high-speed and precise positioning. The rotating components are also driven by a 7.5KW AC servo motor. After the stirrup is processed, a common three-phase asynchronous motor drives the shears through a crank-connecting rod mechanism to cut the rebar, and then the next cycle begins. The S7-300 PLC system programming software used is STEP 7 Professional V5.4 SP4 (to configure FM354 and FM353, we need to install Simatic S7 FM353/FM354 Parameterization Version 4.03.04 provided by Siemens). Modular object-oriented programming is employed to complete hardware configuration, parameter setting, PLC program development, testing, debugging, and documentation. Since STEP 7 Professional V5.4 SP4 supports the simultaneous use of LAD, STL, and FBD programming languages within the same block, ladder diagram programming is used for system logic control, forming FC blocks to implement the electrical control and process logic functions of each unit's actuators. Statement list programming is used for data processing, forming FB blocks. The application of floating-point arithmetic and inverse trigonometric functions greatly simplifies the conversion relationship between the pulse signal input from the external rotary encoder on the detection panel and the rebar feeding length, enabling more complex arithmetic operations, logic, and positioning control functions. The specific program structure is shown in the figure below. Among them, OB100 is the hot start organization block. The system calls OB100 when it starts. Its main function is to initialize various data and reset the various states stored internally. OB1 is the main program block. It calls various FC and FB to update the data in the data block from the MPI bus, controls the servo driver to complete the positioning, controls the action of each valve, and completes the stirrup making action. V. Conclusion After debugging, the PLC and AC servo system work normally and stably in this equipment. The production efficiency of this equipment is about 20 times that of the traditional method. It simplifies the stirrup processing process, greatly improves the production efficiency, improves the working environment of workers, improves the quality of products, and adapts to the current direction of flexible stirrup production. References [1] Li Jianxing, Application Technology of Programmable Logic Controller, Machinery Industry Press, 2004 [2] Yang Zihou, Automatic Control Principles, Metallurgical Industry Press, 1985. [3] Siemens S7-300 Programming Manual [4] Yaskawa Servo Manual [5] Personnel and Education Department of the Ministry of Construction, Steel Reinforcement Worker, China Building Industry Press, 2003. [6] Application of S7-300 PLC in Cold Bending Equipment Zhang Weiguo Author Introduction: Ma Lei, female, born in October 1981, Han nationality, native of Zouping, Shandong, Shandong Xiehe University, mainly engaged in teaching automation major. email: [email protected] Contact number: 15053136629 Lü Duoyong, male, born in June 1982, Han nationality, native of Jinan, Shandong, mainly engaged in electrical design work. Contact number: 15053137259 (250107 Shandong Xiehe University) Ma Lei (250101 Shandong Tianchen CNC Co., Ltd.) Lü Duoyong Contact address: 250107 Shandong Xiehe University (North Campus) School of Mechanical and Electrical Engineering Ma LeiRead next
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