On the type detection and application of Gravure P

2022-07-24
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On the type, detection and application of gravure press tension control

1 Main types and characteristics of tension control

tension control refers to the ability to permanently control the tension of the material belt when it is transported on the equipment. This control must be effective for any running speed of the machine, including acceleration, deceleration and uniform speed of the machine. Even in the case of emergency shutdown, it can ensure that the material belt will not be damaged at all. Gravure press tension control is basically divided into three categories: dynamic tension control, open-loop semi-automatic tension control and closed-loop full-automatic tension control. Manual tension control means that in the process of winding or unwinding, when the coil diameter changes to a certain stage, the operator adjusts the manual power supply device to control the tension. However, the manual tension control system of modern gravure press has been basically eliminated, and only exists as an operation mode in the closed-loop full-automatic tension control system. The open-loop semi-automatic tension control, also known as the coil diameter detection tension control, uses the proximity switch installed at the reel to detect the rotation speed of the reel, and through the set initial value of the reel diameter and material thickness, calculates the current diameter of the winding or unwinding drum accumulatively, and outputs the control signal corresponding to the change of the coil diameter to control the winding torque or unwinding braking torque, so as to adjust the tension of the material belt. Because every revolution of the reel, the coil diameter will change twice as much as the strip thickness. This kind of tension control is not affected by external stimulation and can implement stable tension control. However, the absolute accuracy of this tension control is poor due to the influence of torque variation, linear variation and mechanical loss of the transmission device. The closed-loop full-automatic tension control is to directly measure the actual tension value of the material belt by the tension sensor, and then convert the tension data into a tension signal and feed it back to the tension controller. By comparing this signal with the preset tension value of the controller, the control signal is calculated. The force state execution unit of the automatic control viewpoint makes the actual tension value equal to the preset tension value, so as to achieve the purpose of tension stability. It is an advanced tension control method at present. In addition, the tension control of medium - and high-end printing machines manufactured and sold in China is different at the moment: customers in the industrial chain are everywhere in the conference hall. In the eager inquiry system, the higher printing speed and production process put forward higher requirements for tension control, so that the magnetic powder clutch is no longer competent for the executive unit of this kind of system. Therefore, in modern gravure printing machine, high-speed slitting machine and high-speed coating compound machine, it has been replaced by AC and DC servo motor execution unit, realizing more advanced tension servo control

nb sp; If your machine needs very precise tension control, you must use closed-loop full-automatic tension control. One of the most important links is how to reasonably select the tension detection method. At present, there are basically three tension detection methods:

nb sp; ① Tension sensor (load cell) testing method: it is a testing method that directly detects the tension and is closely combined with machinery without moving parts. Usually, the two sensors are used in pairs, and they are installed on the end shafts on both sides of the detection guide roller. By detecting the load applied by the guide roller, the material belt causes the displacement or deformation of the sensitive element of the tension sensor, so as to detect the actual static test. The standard electronic universal testing machine is used to carry out the tension value, and the tension data is converted into a tension signal and fed back to the tension controller. Finally, the tension closed-loop control is realized. There are many types of elastic sensors in the market, such as leaf spring type micro displacement tension sensor (such as Mitsubishi lx-td type), strain resistance gauge tension sensor (such as Montfort T Series in the United States) and piezomagnetic tension sensor (such as abb pillow series in China), etc. Its advantages are wide detection range, fast response and good linearity. The disadvantages are that it can not absorb the peak value of tension, the acceleration and deceleration of machinery are difficult to handle, and it is not easy to realize high-speed roll switching. Therefore, when the tension control system in the equilibrium state is strongly disturbed, the system will have no time to respond instantly. For example, the amplitude of tension change on the material belt will be large when the inlet temperature of crude oil at the tube side of the condenser on the top of a German crude oil distillation tower is 50  0 ℃, which is unfavorable for the tension control to re-enter the equilibrium state as soon as possible

nbsp; ② Dancer arm tension detection method: it is an indirect tension detection method, which is essentially a position control. When the tension is stable, the tension on the material belt and the force of the air cylinder maintain balance, so that the floating roller is in the central position. When the tension changes, the balance between the tension and the cylinder force is destroyed, and the floating roll position will rise or fall. At this time, the swing rod will rotate around point m and drive the floating roll potentiometer to rotate together. In this way, the floating roll potentiometer can accurately detect the change of the floating roll position. It will feed back the position signal to the tension controller. The controller will calculate and output the control signal to control the servo drive system to correct the deviation. Then the floating roller returns to the original balance position. As the floating roller tension detection device itself is an energy storage structure, it has a good absorption and buffer effect on a wide range of tension jump by using its own residual effect. At the same time, it can also reduce the influence of the eccentricity (ellipse) of the coil and the speed change on the tension. This system requires small cylinder friction coefficient, fast response and stable air source. The weight of floating roller and swing rod shall be light and the rotation shall be flexible

③ floating roller/feedback composite tension detection mode: it can simultaneously detect the floating roller position signal output by the floating roller potentiometer and the tension signal output by the tension sensor, so as to provide the system with higher precision tension control. Its characteristics are: it not only has the function of absorbing or buffering large-scale tension jump by floating roller control, but also has a good buffering and stabilizing effect on the acceleration and deceleration of the machine, and is easy to realize high-speed roll switching. It has the characteristics of high precision and high repeatability of tension sensor closed-loop control. For example, the x/d3000 floating roller/feedback composite tension control device of the American Montalvo company belongs to this type. nb sp;

2. Application of tension controlnbsp

nb sp; ① Touch screen tension numerical control system touch screen tension numerical control device is a full closed-loop automatic tension control system with four section unified control mode. The machine is controlled by the PLC programmable controller. The human-computer interface adopts the HITECH touch screen to set and display the operating parameters. The main control cabinet is used to coordinate the centralized control and operation of unwinding, feeding traction, discharging traction and rewinding. The four section tension refers to the four part tension, i.e. unwinding tension, feeding traction tension, discharging traction tension and winding tension. All four sections of tension are automatically controlled by AC vector variable frequency motor. Receiving material

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