3D printing of metal components through fused filament fabrication (FFF) : a feasibility study

Abstract

Additive Manufacturing (AM), commonly known as 3D printing, is the fabrication process which produces parts by sequentially adding material in a layer-by-layer manner. Fused Filament Fabrication (FFF) has recently enabled the production of metallic components through a three-stage process: printing, debinding, and sintering. This approach has enabled the use of metal-filled filaments, which typically consist of metal powders combined with a polymer binder to manufacture metal components. The primary aim of this dissertation was to investigate the feasibility of manufacturing metal components via FFF. To achieve this, key factors influencing the properties of the final metal parts were analysed. The study began with a comprehensive review of existing literature on metal AM processes, with a particular focus on metal-based FFF. This review provided critical insights into the essential printing and thermal processing parameters, as well as the testing methods used to evaluate FFF-produced metal components. Additional objectives included the design of test specimens in accordance with ASTM and ISO standards, ensuring they met the necessary criteria for mechanical and physical evaluations. A design of experiments (DOE) approach was employed to examine the effects of nozzle temperature and infill overlap on the resulting specimen properties. The primary equipment used throughout the study included the Ultimaker S5 3D printer in conjunction with the Ultimaker Metal Expansion Kit, and the Nabertherm P330 muffle furnace for thermal postprocessing. The testing phase began with visual inspections, which revealed surface discolouration and visible porosity at various processing stages. Post-sintering, the components exhibited notable volumetric shrinkage and warpage, with minimum values recorded at 17.94% and 17.98%, respectively. This significant shrinkage correlated with an increase in density, reaching a maximum value of 8.014 g/cm³, exceeding the standard density of sintered copper. Mechanical testing showed that the highest tensile strength achieved was 124 MPa, while the maximum Young’s modulus recorded was 838 MPa. Surface roughness remained high across all specimens, with hardness values ranging from 31.441 μm to 52.480 μm and peaking at 71.6 HV. Microstructural analysis revealed large grains and low porosity in the copper specimens, with grain sizes ranging from 248 μm to 371 μm and porosity levels between 0.26% to 3.84%.