Friction and Abrasive Wear Behavior of FDM Printed PLA Structures

In rapid prototyping industries - such as aerospace and biomedical engineering - 3D printed polylactic acid (PLA) models used in investment casting require high-quality surface finishes to prevent the transfer of printing defects to the final metal components. Among various post-processing methods, sanding is widely used due to its low cost, ease of control, and ability to reduce surface roughness. This study investigates the abrasive wear and friction behavior of PLA specimens with three infill patterns (linear, triangular, trihexagonal) and three infill densities (50%, 75%, 100%) tested against abrasive papers of four grit sizes (60, 150, 320, 600) under Pin-on-Disc conditions (0.033 m/s, 40 N, 1800 s). The lowest and most stable CoF (~0.55) was recorded with 320-grit paper. Wear rates decreased with increasing infill density for grits 150, 320, and 600, reaching a 50% reduction at 100% density. In contrast, 60-grit tests showed increased wear at higher densities. Surface analysis revealed micro ploughing, and polymeric burr formation. Finer abrasives promoted debris agglomeration on the pin, creating clean "drag bands" on the abrasive disc. These results offer design insights for optimizing 3D printing process parameters to enhance tribological performance in PLA-based components subjected to surface finishing or abrasive contact.