The double seaming process is critical to achieving a hermetic seal for metal cans. Double seaming plays a decisive role in sealing metal cans, ensuring that they are airtight. Personnel involved in can sealing and quality control must undergo rigorous training to ensure the sealing quality of cans.

To achieve a hermetic seal for metal cans, the following three conditions must be met:

• Select the appropriate sealing compound.
• Apply the sealing compound correctly to the can lid.
• Roll-seam the can lid and body, ensuring that their shapes and dimensions meet certain requirements.

It is well known that the sealing structure of double seaming is a stack of metal-to-metal joints. However, it is impossible to achieve an absolutely hermetic seal due to the uneven thickness of the metal substrate. The edge seam of the three-piece can is irregular, and the sealing equipment is continuously worn. To achieve a seal, a layer of sealing compound must be used to fill the leakage channel caused by these reasons.

The formation of double seaming involves two steps:

• The first step involves pressing the flange of the can body onto the curled edge of the can lid, forming an interlocking structure.
• The second step involves pressing the interlocked structure formed in the first step to complete the double seaming.

Because double seaming is completed in two steps, it is called double seaming or double seaming.

Double seaming is accomplished using two rollers in the two-step process. The shape of the rollers used in the first step is different from that used in the second step. The first-step rollers have deeper grooves than the second-step rollers. With the decrease in the size of can seams and the thinning of can-making materials, the design of the rollers has undergone many changes, and the traditional design of the first and second step rollers can no longer meet the needs of modern can-making industries.

During the formation of the double seam and in the final double seam structure, the shape and size of the curled edge of the can lid and the flange of the can body play an important role. In the final double seaming, the curled edge of the can lid becomes the cover hook, and the flange of the can body becomes the body hook. The overlapping part of the cover hook and the body hook is called the seam overlap.

To complete a double seaming process, four equipment components are indispensable, regardless of the type of can seaming machine, whether it is a high-speed machine or a slow-speed machine, and whether it is a multi-head sealing machine or a single-head sealing machine. These four components are the bottom plate, pressure head, first-step roller, and second-step roller.

Yixin Technology is a well-known manufacturer with 30 years of professional experience in metal can-making equipment. We provide one-stop metal can-making services for global customers. Please feel free to contact us at any time with all your professional questions about metal can-making!