The two-roll CNC hydraulic automatic coiling machine completely changed the method of rolling the three-roller coil, eliminating the processes of pre-bending, centering, rolling, and rounding. It is easy to operate, has almost no straight edges, and has a high efficiency. . The coiling process of the two-roller coiling machine was analyzed, and the scheme for realizing the synchronous control precision of the lower roll was introduced.
The three-roller coiling machine must be completed through four processes of pre-bending, centering, rolling, and rounding . The two-roll CNC hydraulic automatic coiling machine completely changes the method of rolling the three-roller coil. The above process can be molded once. The upper roll of the two-roll bending machine is a rigid roll, and the lower roll is a flexible roll. When the lower roll is under the compression of the upper roll, there will be a certain radial concave deformation, when the steel sheet is fed between the upper roll and the lower roll It will be rolled into a cylinder by two pairs of rollers. From a microscopic point of view, the cylinder being rolled is actually composed of numerous segments of small arcs. The rolling process is shown in the following figure.
Rolling process diagram of two-roller coiler
The schematic diagram of the two-roller coiling machine is shown in the figure below. The two-roll CNC hydraulic coiler has two upper and lower rollers, the lower roller is a flexible roller and is a driving roller. The motor is driven by the speed reducer and its coupling. And driven by the hydraulic unit vertical rise and fall, the upper stick is a rigid roller, is a driven roller, is fixedly installed on the machine bed body, when the lower roller rises to contact with the upper stick, the upper stick will rotate together with the lower roller, plastic metal As the plate passes between the upper and lower rollers of the coiling machine, the metal plate is rolled into the desired cylinder. After the rolling process is completed, the lower roller is hydraulically lowered and the roller locking head is opened to remove the product.
Structure diagram of CNC two-roller coiler
Through the analysis of the working principle and structure of the two-roll bending machine, when the top axis of the supporting lower roller rises and falls out of sync, the axis between the two rollers is not parallel as shown in the figure below. This occurs when the cylinder is rolled. One end of the cylinder is calendered so that the diameter of one end of the cylinder becomes larger, which affects the progress of the workpiece. Therefore, the key to improving the processing accuracy of the two-roller coiling machine is to increase the precision of synchronous control while ensuring that the parallelism of the machine tool guide meets the technical requirements.
Numerical control two-roller bending machine axis is not parallel
In the hydraulic control system, due to the characteristics of hydraulic system's liquid compression, leakage, and damping, especially when the external load is large and the external load constantly changes, and the equipment itself is unbalanced and the equipment movement stroke is large, the hydraulic cylinder is realized. The high synchronization accuracy is very difficult, so the research on the design scheme, control method, and synchronization performance of the synchronous system will ultimately relate to whether the actual operation state of the two-roll CNC hydraulic crimping machine can truly meet the design requirements.
In order to achieve the synchronization of the lower roller, two hydraulic cylinders can be used to push the two top shafts. The working principle of the hydraulic synchronous circuit is shown in the figure below. The control circuit mainly consists of an electro-hydraulic reversing valve, a proportional speed regulating valve and a servo valve. The electro-hydraulic reversing valve is mainly used to change the direction of the oil line, so that the lower roller normally rises and falls. The double-ratio directional valve on the main oil line can control the flow rate and speed, and the servo valve is used to control the synchronous operation of the twin-cylinder.
In order to meet the accuracy requirement of the coil, the synchronization between the top shaft 1 and the top shaft 2 must be ensured, that is, the cylinder 1 and the cylinder 2 must be synchronized to rise and fall synchronously, and the adopted scheme realizes synchronous control according to the “master-slave mode”. One of the hydraulic cylinders is the main control cylinder, which is the ideal output. Its movement is the main movement, another cylinder is set as the slave, and the ideal output of the master cylinder is tracked and synchronized.
With the PLC as the core of the entire control system, the signal is given by the PLC. The electronic controller converts its input voltage into the control current of the proportional speed control valve and controls the flow of the valve to control the working speed of the cylinder. The proportional speed control valve 1 receives the speed command signal, and the proportional speed control valve 2 simultaneously receives the speed command signal and the deviation signal of the two hydraulic cylinders, so that cylinder 1 is the active cylinder and cylinder 2 is the slave cylinder. Changing the command signal can change the two. The speed of movement of the cylinder.
The instantaneous displacement of the cylinder is measured by the grating line displacement sensors L1 and L2. The output values are the voltages V1 and V2. The difference between V1 and V2 reflects the inconsistency of the extension length of the two cylinders, which is input as a feedback circuit and amplified. As a system of negative feedback superimposed to the input of the system, so as to immediately correct the displacement, to ensure the synchronized operation of the two-cylinder.
In the rolling process of the roller, in order to avoid the dead zone of the proportional speed control valve and the serious flow nonlinearity, the synchronous precision in the down process of the double cylinder is guaranteed, the hydraulic bypass is added in the hydraulic system, and in the bypass, The domestic servo valve is used to simultaneously control the synchronous downward movement of the twin-cylinder. When the designated position of the coil is reached, the servo valve starts to work and the cylinder 1 is the active cylinder. The two displacement sensors detect the position signals of the two cylinders respectively.
When the two cylinders run asynchronously due to factors such as load imbalance, leakage and geometrical errors, etc., they are detected and compared by sensors, inverter circuits, comparison circuits, etc. The resulting deviation values will be used as control signals to drive the control valves. The valve core makes a slight displacement, so that the cylinder 2 is filled with oil or discharged, and the synchronization error of the two cylinders is compensated until the two cylinders operate synchronously. When this closed-loop control method is used in this system, a synchronous control accuracy of ± 1 mm can be achieved.
Dual-cylinder synchronous control system schematic
The two-roller coiler adopts a numerical control system and uses PLC as the core of the entire control system. The touch screen is used as a man-machine interface. The power line of the system is powered by three-phase 380V and 50Hz AC power. The control circuit converts 380V into 220V and 110V through a transformer. powered by. Control parts and displays are centrally mounted on the operator's console. The control principle is shown in the figure below.
Two roller coiler control schematic
The two-roll CNC hydraulic automatic coiler has completely changed the three-roller coiling method, eliminating the pre-bending, centering, rolling, rounding and other technical processes. The use of hydraulic synchronous control system makes the precision of the rolling circle reach ± 1mm. . The hydraulic servo system of the two-roller coiler adopts double closed-loop control. The error is used to eliminate the error in principle. Therefore, the cumulative error related to the stroke of the hydraulic cylinder is not formed. Practice has proved that the hydraulic system driven by the servo valve guarantees The simultaneous rise and fall of the roller ensures that the gap between the upper roller and the lower roller is the same, which improves the accuracy of the product, is easy to operate, has almost no straight edges, and has a high efficiency, avoids the production of defective products, and greatly improves the work. benefit.
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