Methods and system for mixing and dispensing viscous materials for the creation of additive structures

A method of mixing and dispensing with a mixing and dispensing head of a multi-dimensional printing apparatus, comprising:

• receiving at least two, separate, reactive liquids at a mixing chamber and mixing the at least two reactive liquids within the mixing chamber via rotational motion of a mixing rod;
• adjusting linear movement of the mixing rod positioned within the mixing chamber of the mixing and dispensing head at least along a central axis of the mixing chamber, based on an operating condition of the printing apparatus, and stopping dispensing of mixed liquids from the mixing and dispensing head by stopping one or more pumps fluidly coupled to the mixing chamber and linearly moving the mixing rod upward and away from a dispensing nozzle of the mixing and dispensing head,
• wherein the mixing rod has a tapered section, and the mixing rod is moved in two directions along the central axis, between a fully extended, first position where a distal end of the mixing rod is arranged adjacent to the dispensing nozzle of the mixing and dispensing head and a retracted, second position, where the distal end is moved inward and away from the dispensing nozzle by a threshold distance, the threshold distance being a distance between a bottom of a high pressure bearing and a top of the tapered section in the first position,
• wherein the tapered section has an upper portion that has a first radius and a lower portion that has a second radius, wherein the first radius is greater than the second radius and defines an angled transition between the upper portion and the lower portion, and
• wherein receiving the at least two reactive liquids at the mixing chamber includes receiving the at least two reactive liquids at the mixing chamber via at least two, corresponding, material inlets positioned in an outer wall of the mixing chamber at a vertical position that is within the threshold distance.