The Influence of the 3D Printing Infill and Printing Direction on Friction and Wear of Polylactic Acid (PLA) under Rotational Sliding

We used Fused Deposition Modeling (FDM) for 3D printing of Polylactic acid (PLA) samples, with variation of the printing infill (20% and 100%). Tribological testing was performed on a nanotribometer, under low loads (5, 10, and 15 mN), with a rotating module (ball-on-flat). We studied the friction and wear of PLA samples in two different positions: along the printing direction and normal to the printed direction. The tribological contacts along the printing direction had lower friction coefficient than the contacts that were normal to the printing direction. Samples with 20% infill produced a significantly higher friction coefficient than those with 100% infill. A higher wear factor was exhibited for a dense structure (100% infill) than for a porous material (20% infill). The load increase showed a slight transitional behavior for all types of contacts. The wear factor was on the order of 10–3 mm3/(N m) for all tests.