In the present study, a titanium cellular lattice structure with a mathematical designed porosity gradient was successfully fabricated using the selective laser melting method. The samples with smooth gradient transition of porosity of between 60% and 80% were received for different elementary cell geometries. Elementary cells belong to the triply periodic minimal surfaces family (G, D, I2Y, IWP). Each sample was subjected to a comprehensive analysis including: dimensional metrology and assessment of material defects (X-ray micro-tomography), surface morphology tests (scanning electron microscopy) and mechanical properties (universal testing machine). It has been shown that a cellular lattice with high dimensional accuracy (+0.16/–0.08 mm) and full dense struts can be obtained. According to the assumption, the gradient increases the strength of the cellular lattice samples. The highest increase in plateau stress between the samples with and without gradient was found for the I2Y series (about 185%). Furthermore, it was found that the stress-strain response of the samples depends not only on total porosity, but also on the 3D geometry of the cellular lattice. The stress-strain curves for G, IWP and I2Y samples are smooth and exhibit three characteristic regions: linear elasticity, plateau region and densification region. The size of regions depends on the geometric features of the cellular lattice. For series D, in the plateau region, the fluctuations in stress value are clearly visible. The smoothest stress-strain curve can be noted for the G series, which combined with good mechanical properties (the plateau stress and energy absorbed, at respectively 25.5 and 43.2 MPa, and 46.3J and 59.5J for Gyr_80 and Gyr_6080, which corresponds to a strain of almost 65% and 50%) positively affects the applicability of cellular structures with such geometry.

Research in additive manufacturing of tungsten carbide-cobalt has intensified over the last few years due to the increasing need for products designed using topology optimisation and multiscale structures (lattice). These products result in complex shapes and contain inner structures that are challenging to produce through conventional techniques, thus involving high costs. The present work addresses this problem using a two-step approach to 3D print parts with complex shapes and internal structures by employing indirect selective laser sintering (SLS) and tungsten carbide-cobalt sintering. The paper takes further our research in this field [1] to improve the part density by using high bulk density tungsten carbide-cobalt powders. Mechanically mixing tungsten carbide-cobalt with the sacrificial binder, polyamide 12, results in a homogenous powder successfully used by the selective laser sintering process to produce green parts. By further processing, the green parts through a complete sintering cycle, an average final part density of 11.72 g/cm3 representing more than 80% of the theoretical density is achieved.

This study analyses the three-point bending behavior of Nylon 12 (PA12) specimens produced using two additive manufacturing technologies (i.e., fused filament fabrication and selective laser sintering). A Nylon 12 commercially available filament (from Fiberlab S.A.) was selected to employ the fused filament fabrication method (FFF) with a Prusa 3D desktop printer, whereas Nylon 12 sintering powder (from Formlabs Inc.) was chosen for selective laser sintering (SLS) using a benchtop industrial SLS platform, Formlabs Fuse 1, with a powder refresh ratio of 30%. The bending strength and flexural elasticity moduli were determined by following ISO 178:2019 standard specifications to assess the effect of two different technologies on the mechanical behavior of three-point bending specimens produced in three distinct build orientations (i.e., 0°, 45°, and 90°) relative to the printing platform. One-way ANOVA analysis, Tukey’s HSD, and Games-Howell tests are considered to assess the statistical variability of experimental data and compare the mean values of bending strength and flexural moduli. The testing results for the three orientations under question show notable differences and interesting similarities either in terms of strength or elasticity response for a significance p-level of 0.05.