Effect of Infill Patterns and Print Orientation on the Mechanical Properties of Manufactured Polylactic Acid Parts

Abstract

The fused deposition modeling (FDM) technique produces function models of various thermoplastic polymers and is one of the most commonly utilized additive manufacturing (AM) technologies. The purpose of this research is to study how combining infill pattern (CIP) and printing orientation affects tensile characteristics and building time. Polylactic acid (PLA) was chosen as a material for the specimen's fabrication. The print orientations were the on-long-edge and flat orientations. Because the product is built along the z-axis, the short-edge (up-right) orientation was not considered, resulting in minimal strength. The combinations of the infill patterns called Concentric, Cross, Triangle, Zigzag, Rectilinear, Cubic, Honeycomb, and Grid were investigated with 70% infill density and 0.15 mm layer thickness with a layer-by-layer strategy. The result indicates that the printing orientation significantly affected the tensile strength, especially in CIP specimens. The on-long edge orientation of the CIP specimen had higher tensile strength. The specimen Concentric/Triangle has the highest tensile strength in flat and on-long edge orientations of 30 MPa and 33 MPa, respectively. Still, the building time in flat orientation was long (25 min.) while the printing time in on-long orientation was short (29 min.). The honeycomb/Triangle combination represents lower tensile strength in both orientations of 19 MPa for flat and 20 MPa for on-long edge, but the building time in both orientations was long (14 min and 35 min, respectively). As a result, the specimen with the CIP has greater tensile strength than the single-infill pattern specimen. It was additionally found that when the Triangular pattern was combined with other patterns, the tensile strength of those patterns improved. CIP specimens built in an on-edge orientation had a higher tensile strength than those built in a flat orientation. In the triangle infill pattern, when combined with other patterns, the tensile strength of some samples enhanced while the others improved, while others decreased.