A roll is a tooling that comes either as 1st operation or 2nd operation variant. The second operation roll will then rotate around the can and complete the seam’s formation by “ironing” it and pressing it into a completely closed seam – thus ensuring that the can is hermetically sealed and pressurization is maintained.
The configuration of the roll in a typical seamer head is one chuck (holding the end), a lifter plate (lifting the can and its contents into position) and two rolls. However, there are seamers with more rolls (e.g., 4 rolls per head).
The groove on the 2nd operation roll is typically shaped very similar to the final seam that will be produced by the 2nd operation (assuming that the first operation seam is properly formed).
This is a properly shaped seam after the 2nd operation roll.
The following is a clean profile of a new chuck and 2nd operation roll inside the seamer.
Damaged 2nd operation rolls will typically cause problems in the external dimensions.