Study of defects and dimensional accuracy to determine manufacturability thresholds for laser powder bed fusion of Ti-6Al-4V lattices

Abstract

The degree to which lattice structure fabricated by additive manufacturing (AM) processes matches the original solid model depends on a number of factors, some of which include type of AM process, machine characteristics, and powder utilized. Although some thresholds on dimensions or orientation for 3D-printed simple bars or plates are available in the literature, a large number of variables that influence lattice 3D-printing require thorough investigation. In particular, numerous build orientation for inclined struts, heat dissipation in complex geometry, and structural joints are some unique features of lattices which should be considered while developing associated thresholds. Experimental observation indicated different sizes for similar struts at different locations on a lattice. This requires investigation on the influence of build orientation. In this study, a wide range of strut- and surface-based lattices were designed and fabricated from Ti-6Al-4V in order to study defects and dimensional accuracy. Manufacturability limitations and design considerations were evaluated to achieve a product that was representative of the original design in terms of both geometry and dimensional accuracy. It is demonstrated that below the identified thresholds, the orientation of the lattices on the build-plate influences the homogeneity and dimensional accuracy. Acceptable homogeneity in geometry was achieved for entire lattice structure after orienting 45° around two Cartesian axes. It is demonstrated that support structure should be enough large to facilitate heat dissipation and reduce thermal distortion.