Tool for dispensing multiple materials with discrete positional control without need for sequential tool change

A method for operating a 3D printing tool and assembly for dispensing multiple materials, the method comprising:

• positioning a first material distribution barrel within a first barrel orifice of a barrel holder assembly of the 3D printing tool, wherein:
• the first barrel orifice extends from a top end of the barrel holder assembly through to a bottom end of the barrel holder assembly,
• the first material distribution barrel has a first barrel tip disposed at a first end of the first material distribution barrel positioned proximate to the bottom end of the barrel holder assembly, and
• the first material distribution barrel comprises building material;
• positioning a second material distribution barrel within a second barrel orifice of the barrel holder assembly, wherein:
• the second barrel orifice extends from the top end of the barrel holder assembly through to the bottom end of the barrel holder assembly,
• the second material distribution barrel has a second barrel tip disposed at a first end of the second material distribution barrel positioned proximate to the bottom end of the barrel holder assembly, and
• the second material distribution barrel comprises building material;
• orienting the first material distribution barrel substantially vertically, wherein when the first material distribution barrel is oriented substantially vertically, the second material distribution barrel is oriented at an angle from the vertical within the barrel holder assembly;
• and
• dispensing building material from the first material distribution barrel when the first material distribution barrel is substantially vertically oriented.