A single action press for forming a shell used to make a can end includes
a first tool and an opposed second tool. The first tool includes a die
center insert that performs a forming operation on disc cut from a sheet
of end material. The first tool is configured and arranged wherein force
is supplied to the die center insert during the downstroke and force is
removed from the die center insert at the bottom of the downstroke and at
the start of the upstroke, to thereby enable the die center insert to
disengage from the shell. One specific embodiment uses a die center
piston and compressed air to apply force to the die center insert.
Another embodiment uses a cam and cam follower arrangement to remove
axial forces at the bottom of the downstroke and either springs or gas
pressure to apply force to the die center insert during the downstroke.
Actuators are provided in the first tool to reestablish downward forces
on the die center insert by the time the top of the upstroke so that the
press cycle can be repeated.