Back extrusion process for forming a manifold port

Abstract

A method for forming ports on a heat exchanger manifold, in which risers are back extruded in a single operation from the surrounding material of the manifold such that subsequent machining steps to further define and finish the port are unnecessary. The method of this invention generally includes forging the manifold between a pair of die halves so as to back extrude a localized portion of the manifold into a riser cavity in one of the die halves. Afterwards, and while the manifold remains within the die cavity, a punch is forced through the riser cavity and into the extruded portion in a direction toward the manifold so as to further back extrude the extruded portion. This step causes the raised portion to flow in a direction opposite to the direction of the punch, producing a riser having an internal bore defined by the punch and an outer surface defined by the cavity. An internal chamfer can be simultaneously formed on the internal bore of the riser in order to facilitate assembly of a tube with the riser. The precision of the punch operation yields risers that do not require further machining or finishing to correctly size the risers or form the chamfers.