An Analysis of the Working Principle of Slitting Machines

Slitting machines play a vital role in the field of material processing. They can precisely cut wide rolls of materials into predetermined widths, lengths or shapes, and are widely used in the processing of various materials such as paper, plastic films, and metal foils. Understanding their working principle is of key significance for optimizing the slitting process, improving production efficiency and ensuring product quality.

I. Principle of the Unwinding System
Installation and Fixation of Rolls
The unwinding system of the slitting machine first needs to correctly install the roll to be slit on the unwinding shaft. Usually, expansion-type or chuck-type installation methods are adopted to ensure that the roll will not become loose or displaced during high-speed rotation. For example, the expansion-type unwinding shaft expands the shaft core through internal air pressure or mechanical structure to tightly clamp the inner core of the roll, providing a stable foundation for the subsequent unwinding process.
Tension Control Mechanism
To ensure that the roll is transported smoothly and evenly during the unwinding process, the unwinding system is equipped with a tension control system. This system uses tension sensors to monitor the tension of the roll in real time and compares it with the set value. If the tension is too high, it will cause the roll to stretch, deform or even break; if the tension is too low, problems such as slack and wrinkles may occur during the unwinding process. For example, when the tension sensor detects that the tension is higher than the set value, the control system will automatically adjust the rotation speed of the unwinding motor to slow it down, thereby reducing the tension of the roll; conversely, if the tension is lower than the set value, the motor speed will be increased to increase the tension.

II. Principle of the Cutting System
Types and Selection of Cutters
The cutting system of the slitting machine uses various types of cutters, with round knives and straight knives being common. Round knives are suitable for cutting thinner materials with certain flexibility, such as plastic films and paper. They can generate continuous cutting force through high-speed rotation, and the cutting edges are relatively smooth. Straight knives are more suitable for cutting thicker and harder materials, such as metal foils. The material of the cutters is also crucial. High-quality cutter materials have high hardness, wear resistance and good toughness. For example, cutters made of cemented carbide can maintain sharpness during long-term cutting, reducing the frequency of cutter replacement and improving production efficiency.
Cutting Actions and Adjustments
During the cutting process, the cutters operate according to the set parameters. For round knives, their rotation speed, the contact angle with the roll, and the clearance between the upper and lower round knives need to be precisely adjusted. For example, when cutting thin plastic films, appropriately reducing the rotation speed and contact pressure of the round knives can prevent the films from being stretched or having burrs during the cutting process. Meanwhile, the clearance between the upper and lower round knives needs to be adjusted according to the thickness of the films. If the clearance is too large, the cutting cannot be completed; if it is too small, it will increase cutter wear and cutting resistance. For straight knives, the stroke and speed of their up and down movements as well as their relative position to the roll also need to be precisely controlled to ensure the accuracy and stability of the cutting.

III. Principle of the Rewinding System
Rewinding Methods and Structures
The materials after slitting are collected and organized by the rewinding system. There are central rewinding and surface rewinding methods. Central rewinding involves winding the slit materials around the core shaft of the rewinding roll. The core shaft is driven to rotate by a motor. This method is suitable for situations where higher rewinding tension is required and the materials are relatively thick. Surface rewinding relies on the friction between the rewinding roll and the materials to drive the materials to be rewound. It is suitable for thinner materials with relatively low tension requirements. The rewinding system also includes auxiliary structures such as pressure rollers. The role of the pressure rollers is to closely attach the slit materials to the rewinding roll to prevent problems such as loose winding or air entrainment.
Rewinding Tension and Speed Control
The rewinding system also needs to precisely control the tension and speed. The rewinding tension should match the unwinding tension and remain stable during the rewinding process. If the rewinding tension is too large, the rewound materials will be wound too tightly, resulting in internal stress and affecting the quality of the materials; if the tension is too small, the materials will be wound loosely, which is not conducive to subsequent storage and transportation. For example, at the beginning of the rewinding process, since the diameter of the material roll is small, the rewinding tension can be set appropriately low; as the rewinding process progresses and the diameter of the material roll gradually increases, the rewinding tension needs to be adjusted accordingly to ensure the winding quality of the materials throughout the rewinding process. The rewinding speed also needs to be reasonably controlled according to the overall production efficiency of the slitting machine and the characteristics of the materials. Excessive rewinding speed may cause problems such as material offset and wrinkles during the rewinding process.