Spin-forming method for making catalytic converter

A method for forming a catalytic converter comprising a catalyst substrate, an insulative layer surrounding the catalyst substrate, and a metal housing having a housing midsection surrounding the catalyst substrate and the insulative layer, said method comprising:

• providing a catalyst substrate having a substrate axis and a noncircular substrate circumference about the substrate axis,
• measuring the noncircular substrate circumference, said measuring comprising selecting a reference direction relative to the substrate axis and determining the radial dimensions to the circumference as a function of angular displacement relative to the reference direction,
• wrapping a compressible mat about the catalyst substrate to from a wrapped substrate,
• providing a metal tube comprising a tube midsection having a tube axis,
• coaxially inserting the wrapped substrate into the midsection of the metal tube, and
• spin-forming the metal tube about the wrapped substrate to form the housing midsection, said spin-forming comprising rotating the metal tube about the tube axis, and radially urging while axially advancing a metal-forming roller against the metal tube to reduce the radial dimensions and to compress the compressible mat to form the insulative layer,
• said spin-forming further comprising positioning the metal-forming roller a radial distance relative to the substrate axis and adjusting the radial distance of the metal-forming roller as a function of the angular displacement relative to the reference direction, such that the metal-forming roller is positioned a radial distance relative to the substrate axis equal to the radial dimension of the substrate plus a predetermined radial dimension, whereby the metal-forming roller forms the housing midsection having a shape corresponding to the noncircular circumference of the catalyst substrate and spaced apart therefrom by an insulative layer having substantially uniform thickness.