A 3D printing tool and assembly for dispensing multiple materials includes a barrel holder assembly having at least two barrel orifices extending from a top end of the barrel holder assembly through to a bottom end of the barrel holder assembly, where at least one of the at least two barrel orifices is oriented at an angle from the vertical. A method for operating the 3D printing tool includes positioning a first material distribution barrel within a first barrel orifice, where a first barrel tip is disposed at a first end of the first material distribution barrel. The method further includes dispensing building material from the first material distribution barrel when the first material distribution barrel is substantially vertically oriented and a second material distribution barrel is oriented at an angle from the vertical.