What are the key steps in the working principle of the Three-Roller Automatic Can Sealing Machine?

The working principle of the Three-Roller Automatic Can Sealing Machine is based on the double crimping sealing technology. The three rollers work together to complete the precise sealing of the can body and the can lid in stages. The empty can automatically enters the can sealing machine station through the conveyor belt. At this time, the equipment accurately positions the can body through a photoelectric sensor or a mechanical positioning device to ensure the vertical alignment of the can mouth with the subsequent capping system. Some high-end models use vacuum adsorption or mechanical clamping technology to prevent the can body from shifting during high-speed transmission. The can lid is synchronously supplied by the automatic cover drop device, and is accurately covered above the can mouth through magnetic guidance or mechanical slots.
After positioning is completed, the can tray lifts the can body upward so that the can lid fits tightly with the pressure head. At this stage, the pressure is controlled by the servo motor to ensure the initial fit between the can lid and the edge of the can mouth, providing a stable mechanical basis for subsequent crimping. The pressure head is usually made of wear-resistant alloy material, and the surface is designed with anti-slip patterns to increase friction and prevent the can body from slipping during high-speed rotation.
The core function of the three-roller system is to complete the plastic deformation of the metal curling in layers. The first roller contacts the edge of the can lid in a radial feeding manner, and bends the lid hook of the can lid inward through the rotation pressure, so that it initially bites with the can body hook. At this stage, the "primary curling" is formed, and the overlap rate of the lid hook and the body hook must reach 45%-55%, providing a structural basis for subsequent sealing. The motion trajectory of the roller is precisely controlled by a cam or servo motor to ensure that the pressure is evenly distributed.
The second roller continues the operation after completing the primary curling, further compressing the overlapping part of the lid hook and the body hook, eliminating the metal gap and pressing the sealant layer (such as the rubber or plastic coating on the inside of the can lid). At this stage, the "secondary curling" is formed, and the parameters such as curling thickness and countersunkness must meet international standards (such as the US FDA or EU EN standards). The surface of the roller is usually coated with hard materials such as tungsten carbide to improve durability.
The third roller is used as the final pressing process to shape and flatten the curling, eliminate micro wrinkles or bubbles, and monitor the sealing pressure in real time through a force feedback sensor. Some advanced models integrate laser scanners for non-contact detection of curling width and overlap depth, and abnormal data triggers an automatic rejection mechanism.
During the sealing process, the equipment dynamically adjusts the roller pressure and temperature according to the material of the can body. In the food industry, when the temperature of the liquid in the can reaches 70-90°C, it cools and shrinks after sealing to form a vacuum. The three-roller system needs to cooperate with the cooling air duct to accelerate the curing of the sealing layer. For products that are sensitive to oxygen, the equipment integrates a vacuum chamber to remove the top gap air before sealing. The three rollers complete the final pressing under a negative pressure environment to ensure that the sealant fully fills the microscopic gaps.
The sealed can body is sent out by the conveyor belt, and the equipment is finally inspected by weight detection, air tightness test (such as negative pressure bubble method) or X-ray imaging. The operating data of the three-roller system (such as pressure curve, temperature fluctuation) is uploaded to the industrial Internet of Things platform for production traceability and process optimization.