Additive manufacturing techniques and systems to form composite materials

A coaxial extruder head for a printer comprising:

• a distribution channel with an entrance and an exit;
• a priming chamber comprising:
• an inner wall that separates the distribution channel from the priming chamber,
• an outer wall that surrounds the inner wall and at least a portion of the distribution channel,
• an outlet, and
• a first inlet;
• and
• a nozzle situated at the outlet of the priming chamber, wherein the nozzle converges from the outlet of the priming chamber to an orifice of the nozzle, wherein the exit of the distribution channel extends beyond the orifice of the nozzle.

An extruder head for a printer comprising:

• a first channel with an entrance and an exit, wherein one or both of the entrance of the first channel and the exit of the first channel tapers;
• a second channel;
• a priming chamber including:
• an inner wall that separates the first channel from the priming chamber, and
• an outer wall that surrounds the inner wall of the priming chamber, wherein the second channel merges with the priming chamber at one or both of the inner wall and outer wall;
• and
• a nozzle connected to the outer wall of the priming chamber, wherein an exit of the nozzle is recessed from the exit of the first channel.