Adhesive Distribution on Can Lid

Adhesive Distribution on Can Lid

A qualified can lid must undergo punching, adhesive application, and drying. In addition to a continuous and uniform circumferential distribution, the adhesive film should also have a specific radial distribution.

Radial distribution refers to the distribution of the sealing adhesive away from the cap chuck wall, including the width of the adhesive film, edge distance, and the volume ratio of the adhesive on the cap surface and in the cap groove.

To achieve good radial distribution, it is crucial to select the appropriate adhesive viscosity, solid content, and determine the adhesive volume based on the cap size, nozzle position, and chuck rotation speed. Incorrect selection may lead to excess or insufficient adhesive flowing to the edge. The chuck rotation speed can typically be adjusted by changing gears or installing a variable-frequency motor for the chuck.

Under certain adhesive application conditions, if the viscosity or solid content is too low, the adhesive may flow too quickly, leading to overflow or excessive adhesive in the cap groove. Conversely, if the adhesive viscosity is too high, flow may be insufficient, resulting in a narrow adhesive band or excessive edge distance. In either case, satisfactory adhesive application cannot be achieved. The solution is to either modify the adhesive parameters or adjust application conditions, such as chuck speed or nozzle position.

The ideal adhesive film should be uniform, without visible defects. The film should be continuous, free of breaks, gaps, and air pockets. Notable holes in the adhesive film can compromise sealing integrity. Factors that may lead to breaks or air pockets include improper adhesive weight, incomplete adhesive application cycles, insufficient chuck speed, poor chuck assembly, partial nozzle blockage, or air entrapment during adhesive mixing.