During normal production, it is not enough to measure the seam dimensions. Visual inspection of the can as well as the seam is required at least once every 30 minutes of production.
A visual inspection of the outside of the can is required for detecting visible defects such as:
Of course, a visual inspection also includes cutting a cross section and using a seam inspection system to measure the seam and visually ensure it is correct. A good seam is closed, but not tight enough to break or deform.