Design and extrusion evaluation of a modular 3D printing equipment with a printhead assisted by a single screw

This paper presents the design and extrusion evaluation of a modular 3D printing equipment with a head assisted by a single screw. The adaptive and alternative equipment configurations allow processing material in powder or micro-pellet form, and a distributive mixing capacity that enables the continuous generation of filaments and printed geometries. The design combines a miniaturized modular head - operated under starve-fed or flood-fed conditions - with a benchtop Cartesian platform. The miniaturized modular printhead was prepared to monitor the temperature profile and die pressure. The experimental equipment validation was driven by two approaches: the extrusion effectiveness evaluation and analysis of additive-manufactured beads. The extrusion process was investigated by analytically modeling the pressure profile and experimentally verifying the temperature distribution within the 3D printhead. Additionally, residence time and extrudate swelling were measured. To evaluate the additive extrusion process, bead paths were printed, and based on a parametric analysis of the deposition, V-shaped test specimens were produced and subjected to tensile testing. The main results from the equipment indicated that the temperature gradient (200°C dosing zone – 57°C feeding ramp) of the system is favorable for processing polypropylene. The extruded strands presented regular surfaces and homogeneous morphology. The evaluated residence time is consistent with the conventional extrusion process, and the swelling index is between 1.55 and 1.78. The tensile test specimens exhibited an ultimate tensile strength close to 27 MPa.