Doppelnaht

Doppelnaht, in English known as the double seam, is a sealing method used in metal packaging to join the body of a can with its end. It provides a hermetic seal and mechanical strength by forming two interlocking folds that trap the can end and body together. The double seam is a standard feature in beverage and food cans made from steel or aluminum.

The seam is produced by a double seaming operation, carried out with specialized equipment. During the process, the end is placed on the can body and the edge is curled and interlocked with two sequential sets of rollers. This creates two concentric interlocks, resulting in a continuous seam that resists air, moisture, and leakage. The seam’s integrity depends on precise dimensions, clean tooling, and proper handling of the can materials.

In typical cans, the double seam combines an inner joint and an outer joint, forming a compact, gas-tight seal without adhesives. The end types can vary, including standard pull-tab ends or easy-open ends; the basic seam principle remains the same across configurations. Materials commonly used are steel or aluminum, sometimes with interior coatings to preserve contents and prevent corrosion.

Quality control is essential for Doppelnaht. Seaming standards specify acceptable seam thickness, height, and torque requirements, and manufacturers perform leak tests and visual inspections to detect defects such as improper interlocks, dents, or roll marks. A properly formed double seam is crucial for product safety, shelf life, and transport durability.

See also: seaming, canmaking, hermetic sealing, metal packaging.