Individual station monitoring using press tonnage sensors for multiple operation stamping processes

In multiple operation stamping processes, a press tonnage signal measured by press tonnage sensors installed on press linkages/uprights, is the summation of die forces at all stations. Different front the current practice of using a whole cycle of press tonnage signals to monitor the compound condition of all stations, this paper proposes a new method to use the partitioned monitoring segments of press tonnage signals to monitor individual station conditions. For this purpose, a generic signal segmentation principle is proposed, and the Hotelling T-2 control charts are developed with consideration of the interactions among stations. A real case study of a doorknob stamping process is provided to demonstrate analysis procedures and effectiveness of the developed methodology.