A double-seam is essential for ensuring the protection of contents within a can. This widely-used process is used in the food and beverage industry to create a hermetic seal. Here’s a rundown of the double seaming process.
The double seam is a canning process that creates a bond between the can body and lid. This is achieved by mechanically overlapping five layers of material: three layers of the lid and two layers of the can body. This ensures the contents are kept safe from any contamination or degradation.
The Art of Can Seam Inspection
Examining the integrity of a can seam involves various techniques and measurements, which we’ll outline below based on their effectiveness and cost.
- Seam Thickness: The measurement of the finished seam’s thickness, with a specified range for each can type, helps to assess the pressure applied during the seaming process. It’s typically done with a seam micrometer.
- Seam Height: Also measured with a seam micrometer, this indicates the overall pressure applied during seaming.
- Seam Impression: As the seamer rollers join the cover and body hook materials and press against the seaming chuck, it creates an impression on the inside of the can body. Overpressure can cause damage to the liner.
- Coverhook Wrinkles: Inspecting coverhook wrinkling provides a more accurate indication of proper seaming pressure. The wrinkles that form in the inside radius of the coverhook, due to differences in radius, can be measured to assess seaming pressure and ensure proper seamer operation. To inspect, the coverhook must be removed, but manual removal with nippers is time-consuming and risky. A safer alternative is the Seam Stripper, which slits the top of the coverhook rim for easy removal.
- Double Seam Inspection: A Seam Saw cuts a notch through the seam to visually inspect and measure the various components of the double seam. Three points around the can are typically notched and checked. A visual inspection can reveal flaws in the seam, including overlap, body and cover hook lengths, and proper mating of parts. Vernier calipers can be used for measurement, but video inspection microscopes provide a more precise and thorough inspection.