Can bodymaker diagnostics

A method of detecting defects or deterioration in the sidewalls of can bodies during production of the can bodies within a can bodymaker. Each can body is formed by pushing a cup, mounted on a punch of a reciprocating ram, through one or more dies contained within a tool pack of the bodymaker. The method comprises: obtaining output signals from one or more eddy current sensors arranged around the ram axis outside of the tool pack and adjacent to an exit end of the tool pack; processing the output signals to detect passage of open ends of can body sidewalls past the sensor(s) and thereby determine measures of the heights or thicknesses of can body sidewalls; and analysing the determined measures to identify can body sidewall defects or deterioration.