The Effect of 3D Printing Layer Orientation on the Mechanical Properties of the 3D Printed Trabecular Model

Three-dimensional printing (3DP) is a process that creates solid, 3D shapes by incremental deposition of printing material from sequential 2D layers. The purpose of this study is to determine if printed layer orientation affects the object’s stiffness. Our working hypothesis stated that loading an object perpendicular to its 3D printing layer orientation would result in higher stiffness compared to loading the same object parallel to 3D printing layer orientation. First, five 10-mm3 isotropic solid cubes were 3D printed and tested in compression along their three primary axes. One direction of loading was perpendicular to the printed layers and the two other directions of loading were parallel to the direction of printing. Our results revealed that the cubes behaved stiffer when they were loaded perpendicular to the printed layer orientation compared to when they were loaded parallel to the printed layer orientation. This decrease in stiffness is probably due to induced shear between adjacent printed layers when the sample is loaded parallel to the direction of printing. There was no significant difference in stiffness between the two orientations parallel to the printed layer orientation. Next, two sets of five 18-mm3 orthotropic trabecular bone replicas were 3D printed. Each set of five replicas was printed along a different principal axis. The ten cubes were then tested in compression and the stiffness of identical orientations was compared. Our results demonstrated that, contrary to the isotropic solid cubes, since trabecular structure is orthotropic, one orientation was inherently stiffer than the other, regardless of printing orientatio