Experimental İnvestigation and Numerical Validation of Drilling Machinability in FDM-Printed PLA Parts

Abstract

Fused Deposition Modeling (FDM) is a widely used additive manufacturing technique that fabricates components through layer-by-layer deposition of thermoplastic materials. Due to its biodegradability, dimensional stability, and favorable flow behavior, polylactic acid (PLA) has become one of the most commonly employed polymers in extrusion-based printing. This study investigates the influence of extrusion temperature, infill pattern, and infill density on the mechanical performance and drilling machinability of FDM-printed PLA components. Tensile tests and hardness measurements were conducted to evaluate mechanical behavior, while drilling machinability was assessed through thrust force measurements and digital microscopy. In parallel, a three-dimensional finite element model was developed using ABAQUS/Explicit to capture damage initiation and interfacial degradation, providing numerical validation of the experimental results. The findings demonstrate that infill density is the dominant parameter, with higher densities leading to significant improvements in tensile strength, elastic modulus, and surface hardness. The grid infill at full density and elevated extrusion temperature yielded the highest mechanical performance, achieving a tensile strength of 40.3 MPa and a modulus of 3050 MPa. In contrast, the hexagonal infill pattern offered a favorable balance between mechanical strength and drilling performance, exhibiting reduced thrust force and improved damage resistance. Optimal drilling conditions were identified at 3000 rpm and 150 mm/min, minimizing delamination, burr formation, and thermal damage. Overall, this work highlights the strong coupling between process parameters, internal architecture, and numerical modeling in governing the structural integrity and machinability of FDM-fabricated PLA parts.