A typical sealing machine consists of a frame, a speed reduction and transmission mechanism, a sealing and printing mechanism, a conveying device, and an electrical and electronic control system.
Upon power connection, each mechanism begins operation. The heating elements heat up rapidly, causing the upper and lower heating blocks to reach the desired temperature. The temperature control system adjusts the temperature to the required level. The printing roller rotates, and the cooling system activates as needed. The conveyor belt rotates, and the speed is adjusted to the required speed by the speed control device.
When a package containing goods is placed on the conveyor belt, the sealing portion of the bag is automatically fed between the two moving sealing belts and into the heating zone. The heat from the heating blocks is transferred to the sealing portion of the bag through the sealing belts, softening the film. The film then passes through a cooling zone, where its surface temperature decreases appropriately. Afterward, it is rolled by a knurling wheel (or printing wheel), which adheres the upper and lower plastic films of the sealing portion and presses out a mesh pattern (or printed markings). Finally, a guide rubber belt and the conveyor belt transport the sealed bag out of the machine, completing the sealing operation.
The working principle of a sealing machine mainly includes five stages: heat sealing, pressure sealing, cooling sealing, transmission system, and control system. Heat sealing uses heating elements to soften the plastic bag material at the sealing point. Temperature sensors monitor the temperature in real time to ensure accurate control. Temperature adjustment is achieved by controlling the working time and temperature of the heating elements according to the packaging material and product requirements. Pressure sealing applies pressure to tightly bond the softened plastic film. Pressure control is achieved by adjusting the pressure of the pressure device to control the sealing strength, and the sealing duration is controlled by controlling the working time of the pressure device. Cooling sealing uses a cooling device to quickly solidify and shape the plastic material at the sealing point. Cooling time is controlled by controlling the working time of the cooling device to ensure the sealing strength and stability. The transmission system uses a motor as the power source, transmitting power to the sealing device through a transmission device. The transmission ratio is adjustable to control the speed and force of movement. The control system typically uses a programmable logic controller (PLC) as the control core to achieve automation. Operators set parameters through a human-machine interface, and sensors provide real-time feedback such as temperature and pressure for precise control. Furthermore, with the development of automation technology, high-speed fully automatic sealing machine control systems based on high-performance controllers (such as Siemens SIMOTION D) have emerged. These systems utilize multi-motor collaboration (such as transmission motors, film feeding motors, sealing motors, and residual material motors), photoelectric sensors (photocells) to detect product position and spacing in real time, and employ control algorithms such as cam synchronization. This allows them to achieve a packaging capacity of up to 120 pieces per minute and adapt to the sealing needs of products of different types, sizes, and shapes.