Abstract: An apparatus is provided for liquefying a filament of a solid state material. The liquefying apparatus comprises a hollow tube having a longitudinal length extending between a proximal inlet end and an outlet nozzle at a distal end. The tube defines a passage for passing the material in solid and molten states. A cold block unit is mechanically attached to the tube. A heating block unit is mechanically attached to the tube and positioned along the longitudinal axis of the tube between the cold block and the distal end of the tube for heating the tube to convert the material received at the proximal inlet end of the tube to a molten form. The material advances through the passage from the inlet end to the distal outlet end such that the molten material is extruded from the nozzle for printing each layer of the three-dimensional object.