Exhaust treatment device for automotive vehicle having one-piece housing with integral inlet and outlet gas shield diffusers

A flexible manufacturing process for assembling an exhaust treatment device having opposing ends adapted for attachment to an inlet pipe and an outlet pipe having a one-piece housing, comprising the steps of:

• inserting an exhaust treatment substrate into a cylindrical metallic tube having a fixed diameter;
• reducing the diameter of the tube by swaging such that the substrate is held firmly in place within the tubing;
• spin-forming integral gas shielding diffusers from the tube at opposite ends of the exhaust treatment device, with each of said gas shielding diffusers comprising first concave segment extending inwardly at approximately a 45° angle between a center portion of the housing, and a first convex segment which is tangential to the inlet surface of the substrate, with each of said gas shielding diffusers further comprising a second concave segment having a length which is selected to accommodate the diameter of said tube, with said second concave segment extending between the first convex segment and a second convex segment having a termination to which an exhaust inlet pipe may be attached.