SURFACE ENHANCEMENT OF ADDITIVELY MANUFACTURED INTERNAL CHANNELS THROUGH ABRASIVE FLOW MACHINING PROCESS

Abstract

Additive manufacturing (AM) has emerged as a powerful technology for fabricating complex geometries, particularly internal channels with enhanced functional performance. Among AM techniques, fused deposition modelling (FDM) is widely used due to its design flexibility, cost-effectiveness, and material versatility. However, its layer-by-layer nature leads to significant surface roughness, especially in hard-to-access geometries such as conformal cooling channels, negatively affecting flow behaviour and performance. In this study, a representative conformal internal channel geometry was produced using PLA via FDM and its internal surfaces were enhanced using abrasive flow machining (AFM). Unlike most previous studies focusing on simplified geometries or metallic systems, this work investigates AFM performance on polymer-based FDM channels and integrates experimental results with computational fluid dynamics (CFD) analysis to clarify the surface enhancement mechanism. Surface quality was evaluated using roughness parameters (Ra, Rz), material removal rate (MRR), and surface profile analysis. Results showed that Ra and Rz decreased from 3.08 µm to 0.63 µm and from 28.7 µm to 5.7 µm, corresponding to improvements of approximately 80% and 85%, respectively, with the most significant enhancement occurring during initial cycles. CFD analysis revealed non-uniform pressure and wall shear stress distributions along the channel, explaining variations in material removal. A bidirectional AFM strategy was therefore applied, leading to improved surface uniformity. Overall, the combined experimental and numerical results confirm that AFM is an effective post-processing technique for improving surface quality in FDM-produced conformal internal channels, while providing insight into flow-driven material removal mechanisms and guidance for process optimization in complex geometries.