With the development of the galvanizing process, the quality requirements of the strip welds are becoming higher and higher. Benxi steel galvanizing line introduced a Miebach rapid lap rolling machine from Germany, its model is NBP17. The welding machine has fast welding speed, reliable welding seam quality, equipment operation NBP17 welding machine is mainly controlled by mechanical equipment and electrical System composition. The mechanical equipment is mainly composed of the following 7 parts.
The looper device is mainly used to store a certain amount of strip steel to ensure the free movement, centering and overlapping of the tail of the previous roll of strip and the head of the next roll of strip.
There are 4 sets of centering devices, which are driven by 4 DC servo motors and used to align the head and tail of the strip.
The centering device can ensure that the strip steel is in the center position of the galvanized wire.
After the inlet and outlet lifting rollers are welded, the inlet and outlet lifting rollers are raised to prevent the welding station from being hit by the running strip.
The clamping device is divided into an inlet clamping device and an outlet clamping device, and is equipped with a hydraulic cylinder and a movable joint, which can appropriately adjust the clamping force of the clamping band steel.
The lap table is used to clamp the steel head and move the head forward to produce lap. The lap table is composed of an inlet clamping device and a hydraulic cylinder, and the size of the lap amount is adjusted by the lap amount adjustment device on the loss operation side.
The tilt table is driven by an air cylinder. After the strip is clamped by the outlet clamping device, it is turned downward by a certain angle. After the lap table clamps the strip and moves forward, the tilt table is turned upward and returned to the initial position to complete the lap.
The C-type welding frame is driven by a squirrel-cage AC motor through a screw.
The double-cutting shears raise the lower cutting edge and lower the upper cutting edge before the lap after the clamping device clamps the strip steel. At the same time, the cutting work of the head and the tail is completed to prepare for the next lap.
The strip edge detection device is used to detect the strip edge.
When welding the welding wheel, current is passed and used as an electrode. The upper and lower WF470CRT display system is composed of a display, keyboard and WF470 intelligent template. The WF470 intelligent template is directly inserted into the PLC frame of the welding machine, and is connected through the bus bar on the PLC frame. The WF470CRT display system can exchange data with the welding machine PLC to complete the selection and display of welding parameters and strip parameters, and the diagnosis of welding machine faults. Display and other functions.
The speed of the C-type welding frame and the centering motor is given by the welding machine PLC, and output to the drive device and the servo controller through the analog output board, respectively.
â‘ Sequence control of the welding machine The sequence control of the Miebach welding machine is completed by different sequence blocks (SB) and program blocks (PB), and is called by the organization block OB1. The welding machine automatic sequence control program is as shown.
When a coil of strip is finished, start the automatic sequence control of the welding machine. If the welding machine is ready and there are no other faults, the positioning of the end of the belt starts, and the position of the end of the belt is positioned in front of the exit clamping device. On the center line of the galvanized wire. The positioning of the head of the next roll starts, and after positioning at the entrance clamping device, the head should also be aligned. Immediately afterwards, lbl cut the excess part of the steel head and tail while punching (for welding seam tracking). The steel head and tail are equipped with a communication processor board CP143. Through the CP143 board, the welding machine PLC can be equipped with a galvanized wire Control system S1NECH1 bus, so that the welder can exchange data and signals with galvanized wire. The welding machine receives the strip thickness, quality and interlock signal through the S / NECH1 bus to complete automatic welding.
one of each.
The rolling wheel is installed after the welding wheel, and at the same time of welding, the rolling wheel is squeezed once with a lower pressure to obtain a smooth and flat weld. The thickness of the welding seam is generally not more than 10% of the original plate thickness. 3Welding working principle The welding working principle of lap resistance welding is to lap the two strips according to a certain amount of lap, and pass current to use the resistance of the strip itself, The heat generated by the concentrated resistance between the two strips and the contact part between the strip and the electrode causes the strip temperature at the contact part of the electrode to rise, and finally melts and welds. The formula for the heat generated by the welded joint (ie the weld) is as follows: energizing time; E is the voltage between the electrodes.
It can be seen from equation (1) that the heat generated by the welded joint is related to the welding current, the resistance of the welding zone, the welding time, and the voltage between the electrodes (welding wheel), and the electrode pressure is too high or too low will also produce weld quality influences. Therefore, when welding the steel strip to be welded, a good weld can be formed by controlling the welding current, welding time and electrode (welding wheel) pressure.
4 Welding machine electrical control system The electrical control system of Benxi Steel's galvanizing line Miebach welding machine uses the German Siemens S5-155U series PLC as its logical sequence control part, in addition to the WF470CRT display system, servo controller and thyristor controller Other equipment. The system structure is as shown.
The CPU selected by Mebah welding machine PLC is 946/947, which is composed of CPU946 board and CPU947 board. Due to the interlocking communication dependence during operation, the two boards cannot be operated separately. The CPU has 64Kb of random storage memory, and the use of 355 storage modules can make the memory as large as 896Kb. The scan time of each 1Kb binary statement is 1.4ms with 2048 intermediate flag bits. The system is equipped with 4 32-bit and 4 16-bit digital input boards, as well as 4 32-bit and 4 16-bit digital output boards, and 4 32-bit and 4 16-bit digital output boards. In addition, The system also selects a communication board IM308 that can realize SINECL2 local area network, which is used for the communication between the PLC of the welding machine and the I / O point of the on-site ET200 station. In order to ensure the stability of the automatic welding of the welding machine and the continuous production of the galvanizing line, the welding machine batch must contact the online computer. The system is equipped with the electrical control structure of the welding machine, and the field equipment of the artificial board and output board of the artificial board is overlapped and welded, and the welding seam is rolled by the rolling wheel. After the end, the strip steel is released, and each part of the welding machine returns to the initial position, waiting for the next welding cycle.
Etc.) through the analog output board, output 0 ~ 10V DC voltage value to the thyristor controller. The operator can also set the welding current, welding speed, rolling pressure and other values ​​through the WF470 display system. The maximum welding current is 25kA. In addition, in order to ensure that the working area of ​​the upper and lower welding wheels of the welding machine is on the strip, the system is equipped with a 1P242 counting board and a motor coaxial mounted on the drive C-type welding frame The detection device on the wire frame and the strip edge detection device, when welding, the detection device detects the strip edge, the counting starts, and the actual collected pulse number is compared with the set pulse number in the welding parameter data block. To control the welding current on and off.
The welding transformer has a capacity of 300kVA, and the secondary side outputs a low voltage of about 5V. The output is rectified by a diode (including capacitor filtering) and output to the welding wheel in the form of DC. The upper and lower welding wheels form a loop with the strip steel to be welded to realize direct current welding.
5 Conclusion The automatic sequential control program block diagram of the welding machine â‘¡ Welding current control Welding machine using lap resistance welding, the welding current control is particularly important. The welding current system of NBP17 welding machine is mainly composed of thyristor controller and welding transformer / rectifier. In addition, monitoring elements such as welding flow monitoring, temperature monitoring and voltage monitoring are also designed.
The welding main circuit is powered by three 380V AC. In order to adjust the welding current, there is a program block in the welding machine PLC that specifically controls the welding current. When welding, the welding parameter data block is called according to different specifications of the steel strip (the data block encodes different steels into different serial numbers, and each serial number includes the welding speed, welding current, and rolling pressure. The steel galvanizing line Miebach fast The lap and roll welding machine was put into use in July 1996. The welding machine uses the rolling method to make the thickness of the welding seam reach the level of butt welding, and the welding seam has the advantages of smoothness, flatness and strong welding force. In addition The welding machine uses German Siemens equipment as its control system, which is basically matched with the main control system of the galvanizing line. The data transmission is also accurate and stable and reliable. After 4 years of evaluation and application, it fully meets the requirements of the galvanizing production process. The application effect is good.
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