A method and apparatus is disclosed for additive manufacturing and three-dimensional printing, and specifically for extruding tubular objects. A print head extrudes a curable material into a tubular object, while simultaneously curing the tubular object and utilizing the interior of the cured portion of the tubular object for stabilizing and propelling the print head.

A system (100) for additively manufacturing a composite part (102) comprises a delivery assembly (266), a feed mechanism (104), and a source (116) of curing energy (118). The delivery assembly (266) comprises a delivery guide (112) movable relative to a surface (114) and is configured to deposit a continuous flexible line (106) along a print path (122). The delivery assembly (266) further comprises a first inlet (170), configured to receive a non-resin component (108), and a second inlet (250), configured to receive a photopolymer resin (252). The delivery assembly (266) applies the photopolymer resin (252) to the non-resin component (108). The feed mechanism (104) pushes the continuous flexible line (106) out of the delivery guide (112). The source (116) of the curing energy (118) delivers the curing energy (118) to a portion (124) of the continuous flexible line (106) after it exits the delivery guide (112).