In a can forming machine a system that determines the position of a reciprocating ram and allows for the domer to be repositioned automatically is provided. The system includes a punch position sensor assembly, a control system, and a domer positioning assembly. The punch position sensor assembly is positioned about the ram, preferably at the domer side of the last die. At this location, the punch position sensor assembly can determine the position of the ram as it enters the dieback during the return stroke. The control system receives data from the punch position sensor assembly and, if the ram is not substantially, concentrically aligned with the die pack on the return stroke, sends a signal to the domer positioning assembly to reposition the domer. This process may be repeated until the ram travels along a path substantially aligned with the die pack on the return stroke.