Multi Jet Fusion printed lattice materials: characterization and prediction of mechanical performance

Abstract

Multi Jet Fusion (MJF) is a powder-bed fusion (PBF) additive manufacturing process that enables high-resolution, rapid fabrication of large-scale polymer parts. In particular, the MJF process enables direct printing of structures without the need for support material, enabling complex geometries such as lattices and scaffolds to be manufactured with minimal post-processing. The lattice structure is a highly tunable geometry that can form the stiff, strong backbone of larger-scale designs, facilitating time and material efficiency in the printing process compared to a solid body. While the benefits of lattice-based designs produced with powder-bed fusion processes are clear, there currently exist few studies that empirically characterize the mechanical performance of lattices printed using MJF. In this work, we treat each lattice as an assembly of components (beams and nodes), with each component defined by its nominal size and orientation. To study the effect of changing these parameters on material properties, lattice unit cells of structural interest are modeled with their beam diameters, node sizes, and unit cell geometries varied. Specimens are printed using polyamide (PA)-12 powder, then mechanically tested to determine strength and stiffness. The results are used to determine empirical fitting parameters to the Gibson–Ashby scaling model of lattices, previously unapplied to MJF-printed structures. To further develop a model of the structure's geometry-dependent behavior, the varying failure modes of printed lattices are also characterized. The results of this work provide a foundation for the design optimization of lattices printed using Multi Jet Fusion, in turn developing a fundamental model for a variety of large-scale printable structures.