Dimensional and mechanical characterization of nylon lattice, spring, and non-assembly designs fabricated with selective laser sintering

Abstract Selective laser sintering (SLS) is a promising additive manufacturing process for design innovation, particularly for integrated systems with non-assembly parts. In this paper, minimum size features and mechanics for SLS parts are analyzed to inform the design and characterization of nylon lattices, springs, and joints using prosthetics as an exemplary framework. These characterizations inform the printing of complete nylon consolidated parts using SLS, which was demonstrated with fully functional parts printed without the need for any further assembly. Material testing demonstrated that the prints have low anisotropy with elastic moduli from 770 to 920 MPa for varied print orientations and tension/compression cases. Lattices with body-centered cubic unit cells with 30% and 50% relative densities had effective elastic moduli ranging from 18 to 45 MPa. Helical springs with 3–7 mm wire diameters showed a tunable stiffness from 0.3 to 16.8 N/mm. Springs demonstrated a minimal loss in strength after 20 cycles. A finger prosthetic designed with 0.2-mm gap sizes between components was printed that demonstrated a non-assembly print of functioning joints. Overall, the work demonstrates SLS’s manufacturing constraints and mechanics for consolidated designs with non-assembly mechanisms that enable innovation across wide-ranging engineering.