An apparatus for forming an upper edge of a paperboard container having a bottom and a sidewall terminating at a curled rim at the upper edge, the apparatus comprising: a pocket including a shell having a cavity with a mouth configured to receive the container such that the rim extends beyond the mouth and the container is centered along an axis of the pocket, the rim being formed with a curl thereon; and a flattening station configured to provide compression and flattening of the curl formed on the rim, the flattening station including a cam coupled to a forming member having a first forming surface, the cam and the forming member being moveable back and forth relative to a support (242,244,246) along the axis of the pocket, the cam including an inclined cam surface; and a set of forming arms pivotally coupled to the support and positioned outside the forming member for movement relative thereto, the forming arms being axially moveable together with the cam and the forming member, each of the forming arms having a cam follower engaged with the cam, and a forming segment having a second forming surface facing the first forming surface, wherein when the forming member is moved along the axis to a first position the first forming surface contacts an upper end of the curl on the rim and the cam follower moves along the inclined surface such that the forming arms pivot toward each other to position each second forming surface spaced from and adjacent to a lower end of the curl on the rim, wherein in response to further axial movement of the cam and the forming members past the first position, the cam follower moves off the inclined cam surface and each second forming surface moves axially towards the first forming surface of the forming member to form a flattened rim on the container. a pocket including a shell having a cavity with a mouth configured to receive the container such that the rim extends beyond the mouth and the container is centered along an axis of the pocket, the rim being formed with a curl thereon; and a flattening station configured to provide compression and flattening of the curl formed on the rim, the flattening station including a cam coupled to a forming member having a first forming surface, the cam and the forming member being moveable back and forth relative to a support (242,244,246) along the axis of the pocket, the cam including an inclined cam surface; and a set of forming arms pivotally coupled to the support and positioned outside the forming member for movement relative thereto, the forming arms being axially moveable together with the cam and the forming member, each of the forming arms having a cam follower engaged with the cam, and a forming segment having a second forming surface facing the first forming surface, wherein when the forming member is moved along the axis to a first position the first forming surface contacts an upper end of the curl on the rim and the cam follower moves along the inclined surface such that the forming arms pivot toward each other to position each second forming surface spaced from and adjacent to a lower end of the curl on the rim, wherein in response to further axial movement of the cam and the forming members past the first position, the cam follower moves off the inclined cam surface and each second forming surface moves axially towards the first forming surface of the forming member to form a flattened rim on the container. a cam coupled to a forming member having a first forming surface, the cam and the forming member being moveable back and forth relative to a support (242,244,246) along the axis of the pocket, the cam including an inclined cam surface; and a set of forming arms pivotally coupled to the support and positioned outside the forming member for movement relative thereto, the forming arms being axially moveable together with the cam and the forming member, each of the forming arms having a cam follower engaged with the cam, and a forming segment having a second forming surface facing the first forming surface, wherein when the forming member is moved along the axis to a first position the first forming surface contacts an upper end of the curl on the rim and the cam follower moves along the inclined surface such that the forming arms pivot toward each other to position each second forming surface spaced from and adjacent to a lower end of the curl on the rim, wherein in response to further axial movement of the cam and the forming members past the first position, the cam follower moves off the inclined cam surface and each second forming surface moves axially towards the first forming surface of the forming member to form a flattened rim on the container.