Speaker
Description
Triply Periodic Minimal Surface (TPMS) structures have the potential to effectively tune the mechanical stiffness of orthopedic implants to mitigate stress shielding. To achieve the requisite low modulus, lattice wall thicknesses must approach the physical limits of Laser Powder Bed Fusion (L-PBF). While existing literature predominantly evaluates process parameters for walls thicker than 0.3 mm, a critical gap remains in fabricating sub-0.3 mm features and transferring parameters optimized on simple thin-walled specimens to complex TPMS structures.
This study evaluates the transferability of L-PBF scanning strategies across a 0.10-0.50 mm thickness spectrum in Ti-6Al-4V. We compared five strategies: a standard strategy optimized for bulk parts, contour-only, hatch-only, and two strategies optimized for thin-walled parts. Results show that the bulk strategy caused severe over-melting and dimensional inaccuracy in ultra-thin walls. Although the contour-only and thin-walled optimized strategies yielded high dimensional accuracy with deviations lower than 10%, contour-only strategy exhibited significant lack of fusion (LoF) porosity of up to 6%. The most effective baseline for simple walls was achieved using thin-walled strategy for thicknesses below 0.35 mm and bulk strategy for thicker sections, ensuring minimal porosity and high geometric fidelity.
However, applying these parameters to gyroid structures revealed that complex geometry significantly influences defect formation. Micro-CT analysis identified LoF porosity concentrated specifically at overhanging wall intersections, where the projected cross-section becomes artificially thicker. Quasi-static compression testing revealed a decrease in mechanical properties with increasing porosity rate, with overall mechanical performance falling below finite element analysis predictions. Based on these findings, we propose a hybrid strategy. Applying thin-wall optimized parameters exclusively to the border contours to preserve geometric accuracy, and assigning standard bulk parameters to the internal hatching to fully densify the thicker intersections. This approach offers a readily implementable path to eliminating geometry-driven defects and maximizing the mechanical reliability of ultra thin-walled TPMS implants.
| Speaker Country | Czech Republic |
|---|---|
| Would you like to publish your paper in the special issue of BHM "Berg- und Hüttenmännische Monatshefte" | No |