Polymers and metals are usually combined together in powder metallurgy manufacturing processes: polymers have the double role of binding the metallic powders and controlling the rheology of pastes for injection molded or extruded parts. After shaping, polymers are removed by mean of a de-binding step.
Additive manufacturing technologies, such as Selective Laser Sintering (SLS) and Electron Beam Melting (EBM) allow for the production of metallic components possessing complex geometries, without the use of organic binders. However, pores or holes are often present, due to uncomplete sintering or design constraints. The main advantage of these 3D printing technologies is their flexibility that allows for the production of complex geometries without the need of moulds. Consequently, production costs are deeply reduced especially when only small batches are needed. The disadvantage is related to the high cost of printing units.
In this work, we developed a different approach that consists on the use of a low cost robocasting printer to print metallic inks (Ti6Al4V and steel). A proper ink formulation was realized by controlling the rheological properties of the paste with a proper use of a polymers mixture into a water dispersion. After, printing and drying, the components were sintered under high vacuum.
Highly porous metallic scaffolds with different geometries (up to 65% total porosity) were printed by direct ink writing. The morphology and composition of the metallic scaffolds were analysed, so as the influence of the porosity and geometry on the mechanical behaviour of the scaffolds.