A method and apparatus are provided for producing a multicomponent feedstock being delivered through a print head of a 3D printer. Multiple component lengths are produced from separate feedstocks and are aligned to form the multicomponent feedstock which is fed into the print head for extrusion. The method includes providing at least two sources of feedstock of different material, feeding a distal end of a first feedstock along a feed path, cutting the first feedstock at a pre-determined length to provide a length of first feedstock having a proximal end. The method includes feeding a distal end of a second feedstock along the feed path and aligning the distal end of the second feedstock with the proximal end of the length of the first feedstock. The second feedstock is cut at a pre-determined length to provide a length of the second feedstock serially aligned with the length of first feedstock, to form a length of multicomponent feedstock. The length of multicomponent feedstock is fed into the print head.

A system can comprise a plurality of containers that are coupled together as a movable unit. A plurality of container-feeding assemblies can be configured to simultaneously deliver respective yarns into respective containers of the plurality of containers. A header can be selectively attachable to a tufting machine, the header having a longitudinal axis. A retainer can be configured to extend across the header along the longitudinal axis to secure the respective yarns in respective positions relative to each other along the longitudinal axis.