Methods for making layered tubular structures

A process for winding a convolutely wound tubular structure having a machine direction, a cross-machine direction coplanar thereto, and a Z-direction orthogonal to both said machine- and cross-machine directions, said process comprising the steps of:

• a) providing a first sheet metal supply coil comprising a first sheet metal;
• b) disposing said first sheet metal supply coil on an uncoiler;
• c) unwinding said first sheet metal from said first sheet metal supply coil with said uncoiler;
• d) directing said first sheet metal to a recoiler;
• e) providing said recoiler with a mandrel, said mandrel having a defined geometry, said geometry providing said convolutely wound tubular structure with a desired internal cross-sectional shape and size;
• f) disposing a leading edge of said first sheet metal on said mandrel,
• g) rotating said mandrel to coaxially dispose said first sheet metal about said mandrel to form a first inner region of said convolutely wound tubular structure and provide said first inner region of said convolutely wound tubular structure with a first desired thickness;
• h) when said first inner region of said convolutely wound tubular structure attains said first desired thickness, severing said first sheet metal in said cross-machine direction, forming a first tail portion of said first inner region;
• i) attaching said first tail portion of said first inner region to a previous convolution of said first inner region of said convolutely wound tubular structure;
• j) removing said convolutely wound tubular structure from said mandrel;
• k) prior to said step j), attaching a second sheet metal to said first tail portion of said first inner region;
• l) Rotating said mandrel to coaxially dispose said second sheet metal about said tubular structure to form a second region of said convolutely wound tubular structure comprising the second sheet metal and provide said second region of said convolutely wound tubular structure comprising the second sheet metal with a desired thickness;
• m) when said second region of said convolutely wound tubular structure comprising the second sheet metal attains said desired thickness, severing said second sheet metal in said cross-machine direction forming a second tail portion;
• and,
• n) attaching said second tail portion to said second region of said convolutely wound tubular structure.