Apparatus for piercing hydroformed part

Abstract

An apparatus for in-die piercing of a tube as it is hydroformed creates a sharp edged, non countersunk hole, while sealing against pressurized fluid loss and ejecting the slug cleanly from the apparatus. A sharp edged die button inset into one of a pair of die blocks includes a hole shaped cutting edge surrounded by a compliant face seal flush with the cavity between the die blocks. A plunger is slidable within a central bore in the die button from a closed position flush with the cutting edge to a partially retracted pierce position, and finally to a further retracted ejection position. An ejection chute in the same die block opens into the bore at one end, at a point between the pierce and ejection positions of the plunger, and also opens at the other end out of the die block. The plunger is sealed relative to the die button bore. The plunger is retained in closed position until the tube is fully hydroformed to final shape, and the outer surface of the tube engages the face seal. Then, the plunger is retracted to pierce position, allowing a slug to be blown out through the cutting edge. The face seal and plunger seal prevent the loss of fluid. Then, the tube is de pressurized, and the plunger retracts farther, allowing the slug to be ejected.