Abstract: In recent years, nonwoven fabrics have been increasingly used in various aspects of production and daily life. They are soft, lightweight, and elastic, and also exhibit excellent performance in ventilation, filtration, heat insulation, water absorption, and waterproofing. Therefore, the demand for their application in hygiene products, medical supplies, synthetic materials, waterproofing materials for buildings, and environmentally friendly filtration materials is growing rapidly.
With the trend of nonwoven fabric production lines towards large-scale, high-efficiency, and high-speed development, the product rolls are also tending to be produced in the form of large roll diameter, large roll length, full width without edge trimming or slitting, and then undergo secondary processing on slitting machines. Therefore, slitting machines have become an indispensable and important piece of equipment in nonwoven fabric production, and the performance of slitting machines directly affects the final quality of the fabric rolls.
Functions and main structure of a slitting machine
Functions of a slitting machine
A slitting machine cuts the edges of a full-width fabric roll and then slits it into narrower products for different uses. The minimum slitting width depends on the machine model and the slitting blades, and is generally between 80mm and 100mm .
Main structure of the slitting machine
1. Unwinding device
The unwinding device is used to clamp the fabric roll to be unwound, and the fabric roll moves unwinding during equipment operation. The unwinding device has its own drive mechanism, which actively releases the fabric roll from the master roll . The active unwinding mode is suitable for applications with large roll diameters and a wide range of product specifications, and is currently the mainstream operating mode for large slitting machines.
2. Tension detection device
Tension detection devices typically use tension sensors, which are mounted on the bearing housing of the tension roller . The tension roller is usually located at the unwinding exit end or the winding entrance end and is fastened to the frame.
3. Slitting device
The slitting device is the main working mechanism of the slitting machine, including the slitting blade, blade holder or blade shaft, adjustment and positioning mechanism, and blade feed and retraction mechanism. The blade shaft is driven by a frequency converter , which drives the blade to rotate at high speed.
4. Winding device
The slitting machine uses a surface friction winding method, with two parallel , identical winding rollers approximately 300-400 mm in diameter. The roller surfaces are specially treated to achieve appropriate hardness and friction, along with a stable coefficient of friction . The two rollers are independently driven, allowing for adjustable surface linear speeds. By combining adjustments to the speed difference between them with changes to the pressure of the pressure rollers , the winding tension or diameter can be precisely controlled.
Electrical control section of the slitting machine
The slitting machine is designed with a constant tension control system. This automatic tension control system can set the winding tension according to process requirements and maintains a stable tension throughout operation , regardless of changes in roll diameter. Tension fluctuations can affect the flatness of the slitting surface and even cause adjacent rolls to overlap and become difficult to separate. Therefore, stable tension control is crucial for product quality.
The overall control system adopts an HMI+PLC+VF mode. The HMI controls start/stop, tension setting, pneumatic valve opening/closing, and monitoring of operating data, while the PLC ... The logic operation and control output are handled by the frequency converter actuator, which drives the motor. The control requirements for the cutter motor in the cutter unit are relatively low; ensuring stable speed without fluctuations during operation is sufficient. Therefore, the more economical FC360 series frequency converter is selected for its drive.
The winding device employs a surface winding mode, with two parallel rollers driven independently, one as the main winding and the other as the slave winding. The main winding inverter uses the FC302 series , employing a speed closed-loop control principle as the primary speed controller . The slave winding inverter also uses the FC302 series, employing a torque closed-loop control principle with speed limiting. Because the slave winding primarily provides reverse torque, the inverter always operates in reverse power generation mode. A braking unit and braking resistor are required to dissipate excess energy. The magnitude of the reverse torque during slave winding can adjust the winding tension, i.e., the winding tension itself. The unwinding device uses an active unwinding mode, employing the Danfoss FC302 series inverter. This high-performance, general-purpose vector control inverter features a modular design and powerful functionality, capable of driving AC asynchronous motors, permanent magnet synchronous motors, reluctance motors, etc. The control mode uses a free PID speed closed-loop, offering high speed accuracy and fast dynamic response. The encoder signal from the unwinding motor is used as speed feedback to achieve speed closed-loop control. The tension signal fed back by the tension sensor of the detection device is used as tension feedback, and the tension set value on the human-machine interface is used as the target tension to achieve process closed loop.
By using the system linear velocity signal as the feedforward input signal, a free PID speed closed-loop overall control is achieved. This control mode makes tension control more stable and precise, ensuring consistent tension control even during acceleration and deceleration.
Summarize
The Danfoss FC302 series high-performance frequency inverters, with their reliable hardware, powerful software, and diverse control principles, fully meet the control requirements of various parts of large slitting machines . Their free PID mode ensures stable and consistent tension control with high precision and fast response, earning consistent praise from customers.
