double seam defects
Vee is an irregularity on the cover hook when the cover does not form smoothly. The material splits causing a V-shaped opening in the face of the cover hook.
pleats, puckers & spurs
A Pleat is a fold in the cover hook that extends from the cut edge downward toward the cover hook radius and sometimes below this radius in a sharp vee or spur.
As the rollers push the cover and body hook materials together, and against the seaming chuck, an impression is left on the inside of the can body. Too much pressure can cause this impression to damage the can liner.
A seam bump is a short area of the double seam where the seam thickness suddenly increases by .004″ or more.
A sprung seam is a condition where the seam is pulled away from the body wall. In some extreme cases, the seam is pulled away from the body wall the entire way around the can.
A sharp seam is a condition where the seam has a sharp edge or radius on the upper inside edge of the countersink wall.
A false seam is a critical defect which occurs when the cover and the body hooks do not interlock around the can seam’s circumference.
knocked down flange
Knocked down flange is a critical defect. It occurs when the cover and body hooks do not interlock in a localized area of the double seam. Typically 1-2 inches in length.
Dead head is a condition where the first and/or second operation seam is not completely formed around the circumference of the can.
loose first operation seam
A loose first operation seam may not allow sufficient tuck up of cover curl to form a sufficient amount of cover hook and overlap.
tight first operation seam
A tight first operation seam can create flatness on the bottom of the first operation seam throughout its length. The cover hook may also be turned back into the body hook.
A more reliable indication of proper seaming pressure is obtained from inspecting the coverhook wrinkling. Because of the difference in radius, as the various parts of the seam are pressed together, wrinkles will naturally occur in the inside radius of the coverhook. Measuring the depth, type and quantity of these wrinkles will help you to determine that the correct pressure is being applied, and ensure your seamer is operating properly.
In order to inspect the coverhook for wrinkling, however, it needs to be removed from a completed seam. It is possible to remove it manually with a pair of nippers, but the process can be time consuming, and a bit dangerous. Not to mention, the possibility of damaging the very thing you are attempting to inspect.
A long cover hook is a condition where the cover hook length approaches or exceeds the specification.