An extrusion head comprising at least one mounting structure, a first liquefier pump secured to the at least one mounting structure, a second liquefier pump disposed adjacent to the first liquefier pump, a toggle mechanism supported by the at least one mounting structure and configured to move the second liquefier pump relative to the first liquefier pump along a first axis, and a slot engagement assembly connected in part to the second liquefier pump for defining a range of motion for the second liquefier pump along the first axis.