A method of processing a plate element by a processing device mounted on a lateral side of a packaging production machine, the packaging production machine feeding the plate element in a longitudinal direction at an operating speed, the processing device comprising:
- a hub supported and configured to rotate about a substantially horizontal first rotation axis transverse to the longitudinal direction;
- two tools mounted on the hub spaced apart around the first rotation axis, a first tool of the two tools configured to process the plate element at a first processing position of the first tool, and a second tool of the two tools being configured to process the plate element at a second processing position of the second tool, the first tool being configured to process the plate element at a front lateral processing position on the plate element, and the second tool being configured to process the plate element at a rear lateral processing position on the plate element, wherein the front lateral processing position and the rear lateral processing position are along a lateral edge of the plate element;
- a hub drive configured to drive the hub and the two tools in rotation around the first rotation axis;
- a counter-tool supported and configured to rotate about a second rotation axis that is substantially horizontal, transverse to the longitudinal direction, and parallel to the first rotation axis of the hub, the plate element being engaged successively between the first tool and the counter-tool and between the second tool and the counter-tool;
- and
- the hub drive being configured and operable to drive the hub at a speed of rotation that varies during a rotation cycle of the hub,
- wherein the method comprises:
- operating the processing device;
- controlling the hub drive to implement a first phase and a second phase of the rotation cycle, during an entirety of the first and second phases, the hub being driven at a constant speed substantially equal to the operating speed, such that in the first phase the first tool is in the first processing position for processing the front lateral processing position on the plate element and in the second phase the second tool is in the second processing position for then processing the rear lateral processing position on the plate element;
- and
- controlling the hub drive to implement at least one third phase of the rotation cycle, the at least one third phase occurring after the first phase and before the second phase, and during the at least one third phase, driving the hub at a non-zero rotation speed that is different from the constant hub rotation speed and is set according to a distance on the plate element between the front lateral processing position and the rear lateral processing position,
- wherein during the at least one third phase, each of the two tools is moved through a respective intermediate position, in order to reach the corresponding first processing position and the second processing position for processing the plate element at, respectively, the front lateral processing position and the rear lateral processing position;
- and
- operating the counter-tool to have a speed of rotation throughout the at least one third phase that is substantially equal to the operating speed.