After printing and coating, the aluminum foil needs to be cut on the slitter. The large volume of semi-finished products are cut to the required size. The semi-finished products running on the slitter is a process of unwinding and winding. This process includes two parts: speed control and tension control of the machine. The so-called tension is in order to pull the aluminum foil and roll it to the core according to the standard, it is necessary to apply a certain pulling force of stretching and tensioning to the aluminum foil, and the control force of tensioning the aluminum foil is the tension. Tension control refers to the ability to control the tension of aluminum foil in the equipment for a long time. 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 stop, it also has the ability to ensure that the aluminum foil does not produce any damage. Slitter tension control is basically manual tension control, automatic tension control. Manual tension control is 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 achieve the purpose of tension control. The full-automatic tension control is to measure the actual tension value of the material belt directly by the tension sensor, and then convert the tension data into the tension signal and feed it back to the tension controller. Through the comparison between the signal and the preset tension value of the controller, the control signal can be calculated. By automatically controlling the executive unit, the actual tension value is equal to the preset tension value, so as to achieve the purpose of stabilizing the tension. The tension setting of winding and unwinding directly affects the yield of the product. If the tension is too large or too tight, the aluminum foil is easy to wrinkle. If the tension is not enough, the aluminum foil is easy to slip on the roll and seriously dislocated, which makes it impossible to unload the roll, and causes the unwinding shaft to swing greatly during slitting, which affects the slitting quality. Therefore, the slitting machine must have a good tension detection system .

1. Unwinding tension detection system of slitter:
Tension sensor detection is a direct detection of tension, which is closely combined with machinery and is equipped with a detection mode of moving parts. Usually, 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 applied load on both sides of the guide roller, the tension sensor sensitive element is displaced or deformed, so as to detect the actual tension value. The tension data is converted into tension signal and fed back to the tension controller and the belt slitter

2. Tension attenuation and tension compensation of slitter winding and unwinding: it is generally believed that maintaining constant tension of aluminum foil during winding and unwinding is conducive to the performance quality of aluminum foil products, but it is not. ******With the increase of coil diameter or weight, the tension of aluminum foil increases according to a certain rule, and the smaller the diameter or weight is, the lower the tension will be. Because there are automatic tension control and manual tension control in slitting operation. Manual tension control requires the operator to adjust the diameter and weight of the masterbatch roll. As shown in the table below:

Aluminum foil cutting weight (kg) manual control power supply voltage value (V) actual tension value (n)

30 5 15-20
60 6 20-25
90 6.5 25-30
120 7 30-35
150 7.5 35-40
180 8 40-45
210 8.5 45-50

The automatic tension control system is a pre-set tension decay value, which decays according to the change of material roll in the process of equipment operation. When setting the automatic tension operation, the initial tension should be set first, and then the tension should be set. Take the attenuation value of slitting aluminum foil unwinding as an example, its setting principle is: aluminum foil tension attenuation (%) is equal to the tension at the end of each winding minus the initial tension, and then divided by the initial tension to get the quotient and then multiplied by 100%. When setting the automatic tension value, it should not be too large, otherwise the surface hardness of aluminum foil winding is large, and it is easy to appear edge warping phenomenon, but the tension should not be too small, too small will cause too loose rewinding body, irregular winding and edge running. Therefore, in the process of aluminum foil slitting operation, the quality of winding and unwinding is mainly affected by the change of aluminum foil tension. It can be seen that the control system of winding and unwinding is the key to the quality.

To sum up, in the process of slitting medical aluminum foil, we should first select the advanced model, and pay attention to understand the characteristics of the tension detection and control system used in the equipment during the operation, formulate reasonable tension for the aluminum foil materials used, as well as the tension attenuation and compensation in the process of coiling and unwinding, so as to realize the soft start and stop of the equipment tension and prevent quality problems. In the process of slitting, we should always pay attention to the change of the tension of aluminum foil, because it is affected by the change of material quality, weight, thickness uniformity and slitting speed. When setting the tension, it must adapt to these characteristics of aluminum foil. In order to ensure the accuracy of the tension of the take-up and take-off mechanism, when the tension detection roller of the take-up and take-off mechanism should be higher than the speed of ensure the stability of product quality.