Research on PLC based on flash butt welding

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PLC research based on flash butt welding

Abstract: This paper analyzes the process of the mechanical mechanism of flash butt welding, and designs the PLC control sequence according to the process of flash butt welding. Using PLC control, on the basis of hardware, through software programming can improve the flexibility of control. Using PLC control can ensure the stability of the control system and the welding quality

key words: flash butt welding; PLC; Mechanical mechanism; As an advanced welding technology, flash butt welding has the advantages of no need to add welding materials, high productivity, low cost, easy operation and so on. With the continuous development of industrial technology, the section of welded parts is getting larger and larger, and some technical problems are encountered, such as difficult welding heating, low productivity, low product qualification rate. In order to solve these problems in flash butt welding, many welding workers have carried out a series of research on the flash butt welding process, and created high-efficiency and low-energy flash butt welding methods, such as pulse flash butt welding method and program reduced voltage flash butt welding method. To control the flash butt welding process and improve the productivity as much as possible on the premise of ensuring the welding quality is the goal we have been pursuing. Considering the factors that affect the quality of flash butt welding, this paper uses PLC system to control the process of flash butt welding, realizes the purpose of welding quality control, and improves the productivity of flash butt welding

1 mechanical mechanism and process analysis

1.1 mechanical device and action of flash butt welding ● standard fixed die aperture: φ 27 ± 0.05mm process

as shown in Figure 1, it is the mechanical device of flash butt welding, and its action process is analyzed as follows:

1.1.1 pre adjustment

preliminary preparation of flash butt welding process, that is, adjustment of mechanical mechanism, selection of welding parameters, etc. The main specification parameters of flash butt welding are: extension length, flash speed, flash current density, upsetting speed, upsetting pressure, clamping force, etc

after debugging, mount the workpiece on the workbench

1.1.2 clamping and positioning

press the start button, the coils of solenoid valves pq1, pq2 and PQ3 are charged, and the compressed gas flows into the upper air chamber of clamping cylinders 1 and 2 through three parts. The compressed gas pushes the piston rod downward to compress workpieces 1 and 2 until the compression switch is closed

at the same time, the gas flowing out of the air pump enters the upper air chamber of the positioning cylinder 3 through the three large pieces, pushing the positioning rod upward to accurately position the workpiece alignment. After positioning, the PQ3 coil of magnetic valve of the mechanical device of electrogram 1 flash butt welding is powered off, and the positioning rod bounces back

1.1.3 welding

turn on the welding switch, keep the solenoid valve P on the induction surface of the switch, and an alternating magnetic field will be generated. Q1, pq2 and pq4 coils are charged, and the solenoid valve pq5 coil is not charged. The pressure gas enters the right air chamber of the propulsion cylinder 4 through the three low-pressure parts, and pushes the piston rod and the moving fixture to drive the workpiece 2 to move towards workpiece 1 until workpiece 1 and 2 contact, reaching the preset position, and the propulsion switch is closed. The moment workpiece 1 and 2 contact, it starts to be powered on and heated. When the flash heating reaches the predetermined temperature, the pq5 coil of the solenoid valve is charged, and the compressed gas is pushed through the high-pressure three parts to push the cylinder and the dynamic fixture to carry out rapid upsetting with great pressure. Then cut off the welding current and keep it for a period of time to cool and solidify the joint. When the welding time is up, disconnect the welding switch and the welding process is over

1.1.4 reset

the coils of solenoid valves pq4 and pq5 are powered off, the air circuit of the propulsion cylinder is reversed, and the low-pressure gas enters the left air chamber of the propulsion cylinder 4 to push the propulsion cylinder to drive the workbench to the right, and the propulsion cylinder 4 is reset. The coils of solenoid valves pq1 and pq2 are powered off, the air circuit is reversed, the compression contact bounces back, and cylinders 1 and 2 are reset. At this time, a flash butt welding process has been completed, and all devices are waiting in situ for the next welding cycle

1.2 timing analysis of flash butt welding

due to the large number of actuator components and the timing of each component action, the process timing diagram is made first to facilitate timing analysis. The welding process of flash butt welding can be summarized as follows: preset - positioning - clamping - pushing - Welding - upsetting - holding - resetting and other stages. Figure 2 shows the sequence diagram of flash butt welding process

2plc control process implementation

2.1plc model selection

plc, namely programmable controller, is a new generation of industrial control device developed on the basis of automatic control technology, microcomputer technology and communication technology. At present, it has been widely used in machinery, metallurgy, chemical industry, welding and other fields. According to the requirements of flash butt welding process, price and many other factors, cpm1a series PLC produced by OMRON company is selected here. The host of this series is divided into 10 points, 20 points, 30 points and 40 points according to the i/o points. In the experiment, a 30 point PLC host with DC24 power supply and transistor output was selected. This model has 18 input points (00000 ~ 0001100100 ~ 00105) and 12 output points (01000 ~ 0100701100 ~ 01003). It has compact structure, strong functionality, high cost performance, and is suitable for small-scale control

2.2 i/o distribution of PLC

according to the requirements of flash butt welding process, 17 input points (00003 ~ 0000900107, and two high-speed counting inputs of 00000 and 00001) and 7 output points (01000 ~ 0100, including 1 KUKA articulated arm robot and 1 integrated infrared heating furnace 6) of PLC are occupied. The specific i/o distribution is shown in the table below

2.3plc and peripheral circuit connection

using programmable controller (PLC) to replace time relay is actually using "soft" relay (programming element) to replace "hard" relay (actual element). In order to achieve this requirement, first of all, the control requirements and action process in the original control system should be analyzed. On the basis of clearly dividing each state of the control process and its action characteristics, the peripheral circuit of PLC should be designed

Figure 3 shows the peripheral circuit diagram of PLC designed according to plci/o distribution table, which can accurately and conveniently control the action process of flash butt welding and realize the purpose of automatic control

3 conclusion

3.1 the mechanical device controls the propulsion and upsetting process of flash butt welding through two gas paths of high-pressure three parts and low-pressure three parts, which not only ensures the accurate stroke of workpiece propulsion, but also meets the high-pressure requirements of upsetting stage, providing convenient conditions for controlling the cycle of flash butt welding. The whole process is easy to operate and highly mechanized

3.2 the control system is different from the previous relay control. The application of PLC control system in the control process of flash butt welding has the advantages of simple circuit, convenient use and maintenance, and high control accuracy. It not only realizes the mechanization and automation of the welding process, but also ensures the flexibility and safety of the operation process. It has a wide application prospect in the field of welding industry

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