Application of Sunwoele VFD (Variable-frequency Drive) on slitting machine

1 Introduction

???In recent years, the papermaking industry and the printing and packaging industry have achieved rapid development and are facing unprecedented huge opportunities. However, compared with the world's advanced equipment, they are also facing huge challenges. The production capacity of the production equipment is very strong, but our products are basically in the low-end market. The main reason is the limitation of technical conditions. At present, a large number of slitting machines still use magnetic powder brakes to control the tension of rewinding and unwinding, which limits the operating speed of the equipment and wastes energy. Moreover, due to the service life of the magnetic powder itself, the failure rate is high. condition.

Sunwoele HSF600 series VFD (Variable-frequency Drive) can carry out constant tension control, and can control the tension taper to ensure the uniform shape of each layer after winding, and greatly improve the operating speed of the slitting machine.

2 Introduction of slitting machine

???Slitting machine is a kind of mechanical equipment that cuts wide-width paper or film into multiple narrow-width materials. It is often used in paper-making machinery and printing and packaging machinery. The simple schematic diagram of the slitting machine is as follows

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???The traditional control scheme of the slitting machine is to use a large motor to drive the rewinding and unwinding shaft. A magnetic powder clutch is added to the rewinding and rewinding shaft. The resistance generated by the magnetic powder clutch is controlled by adjusting the current of the magnetic powder clutch to control the surface of the material. tension.

???Magnetic powder clutch and brake are a kind of special automatic actuator, which transmits torque through the magnetic powder filled in the working gap. Changing the excitation current can change the magnetic state of the magnetic powder, and then adjust the transmitted torque. It can be used for stepless speed regulation from zero to synchronous speed, suitable for high-speed fine-tuning and medium and small power speed regulation systems. It is also used in the unwinding or rewinding tension control system that adjusts the torque by adjusting the current to ensure that the tension remains constant during the winding process.

Its main feature is that the magnetic powder clutch is used as a resistance device, through system control, to output a DC voltage to control the resistance generated by the magnetic powder clutch. The main advantage is that it is a passive device that can control a small tension. Its main disadvantage is that the speed cannot be high, and it is easy to cause high-speed friction of the magnetic powder during high-speed operation, resulting in high temperature, causing the magnetic powder clutch to heat up and shorten its life.

3 Sunwoele VFD (Variable-frequency Drive) control on the slitting machine

plan description:

???Use Sunwoele general-purpose VFD (Variable-frequency Drive) to drive the pressure roller to control the operating speed of the slitting machine. It can work in an open-loop vector mode. The main speed can generally be adjusted with a potentiometer. The AO1 port is used as the output of the operating frequency, as the linear speed setting of the unwinding VFD (Variable-frequency Drive), and the upper and lower winding VFD (Variable-frequency Drive). Unwinding VFD (Variable-frequency Drive) and rewinding VFD (Variable-frequency Drive) must use Sunwoele tension special variable VFD (Variable-frequency Drive). These three kinds of VFD (Variable-frequency Drive) all need to work in closed-loop vector mode, and work in tension open-loop mode.

???Sunwoele HSF600 series VFD (Variable-frequency Drive) is a VFD (Variable-frequency Drive) that can realize constant tension control. The roll diameter of the material can be obtained through the internal calculation of the VFD (Variable-frequency Drive), and the roll diameter of the material can be obtained by controlling the VFD ( Variable-frequency Drive) output torque to obtain constant tension control. Sunwoele VFD (Variable-frequency Drive) can compensate for system inertia, frictional resistance and material inertia caused by system inertia, frictional resistance and material inertia caused by uneven speed during starting or acceleration by setting system inertia compensation, friction compensation and material inertia compensation, and obtain very stable tension Control effect. The scheme is simple and debugging is simple. Moreover, the constant tension control is basically not affected by the speed and can realize high-speed slitting.

??Because the torque control accuracy of the vector control VFD (Variable-frequency Drive) is more than 5% of the rated torque, when the controlled tension is too small, the VFD (Variable-frequency Drive) should output a small torque when the coil is empty. more difficult.

Debugging description:

???When using Sunwoele VFD (Variable-frequency Drive) for cutting machine control, it is recommended to use the motor to directly drive the main shaft without installing a reduction gear. The main reason is that when the VFD (Variable-frequency Drive) controls the tension, the control quantity is finally the output torque of the VFD (Variable-frequency Drive). The torque is the product of the tension and the roll diameter. When the roll is empty, the output torque is the smallest. If the reduction ratio is N, the torque converted to VFD (Variable-frequency Drive) is torque/N. If it is less than 5% of the rated torque of the motor, the control is not accurate enough.

???When debugging, first adjust the closed-loop vector mode of the three VFDs (Variable-frequency Drive) for rewinding and unwinding, otherwise the subsequent torque control cannot be completed. During this process, the most frequently encountered problems are that the encoder signal is not input, the directions of the rotary encoder A and B are reversed, and the number of encoder pulses is incorrectly input. The manifestations of these problems are mainly due to the large deviation between the operating speed and the input speed or the low-speed creep of the motor and the large difference between the operating current and the actual no-load current.

???In unwinding control, VFD (Variable-frequency Drive) actually only provides a reverse tension, so its control accuracy is not high. Debugging is relatively simple. Regarding the reverse tension at zero speed, Sunwoele VFD (Variable-frequency Drive) can provide two options. One is to allow the reverse tension function. The manifestation is that if the running command is not removed at zero speed, the VFD ( Variable-frequency Drive) can control the motor to tension the material all the time, avoiding the speed impact caused by the material relaxation at the beginning of the operation, and the material will be broken. Another option is to not allow reverse tightening. If the running command is not removed at zero speed, the VFD (Variable-frequency Drive) will have no torque output. The material may be loose, but it can avoid the running-away situation when the material is broken.

???The rewinding VFD (Variable-frequency Drive) works in torque control mode. During acceleration and deceleration, it is necessary to provide additional torque to overcome the moment of inertia of the system. If no compensation is added, the tension will be too small during the winding process and the tension will be too large during the deceleration process. If the tension decreases when starting, increase the system inertia compensation coefficient. The friction compensation is mainly to overcome the influence of the friction force existing in the system on the tension during the whole operation process, and it can be completed by adjusting the friction compensation coefficient. If the material tension is less than the set tension during normal operation, the friction compensation coefficient will be increased. Another thing that needs to be compensated is the moment of inertia generated by the material on the reel. By setting the density and width of the material, the VFD (Variable-frequency Drive) can calculate the moment of inertia of the current material. When debugging, set the tension taper appropriately to control the curling quality of the material and avoid the occurrence of tightness and looseness inside.

???In many cases, the winding diameter is obtained through the linear speed calculation method, and the winding diameter is a direct factor in calculating the output torque, so it is very important to correctly set the maximum linear speed. During debugging, you can verify the current roll diameter and actual roll diameter displayed by VFD (Variable-frequency Drive) to determine whether the set maximum linear velocity is correct. If the displayed current winding diameter is greater than the actual winding diameter, it indicates that the maximum linear speed set is too large.

???By setting the above several compensation quantities, the influence of system inertia on addition and subtraction can be effectively changed. Setting proper tension can achieve better winding control.

Concluding remarks

???Because the use of VFD (Variable-frequency Drive) to control the winding and unwinding control of the slitting machine overcomes the inherent weakness of the magnetic powder, the control of high-speed slitting becomes a reality, and the reliability of the equipment is greatly improved, and there is no cost. Excessive increase, so more and more customers are beginning to use VFD (Variable-frequency Drive) to realize slitter control.