Though the use of fused deposition modeling (FDM) of polymers is ever increasing, their utilization in applications requiring high-strength and high-quality surface finish is limited. The process-inherent voids in-between deposited layers and the coarse outer surface resulting from freeform deposition are the critical deterrents. Applying ultrasonic vibration post-fabrication could minimize these issues. In this study, we FDM printed ASTM D638 Type IV specimens from PLA using LulzBot Taz Pro-S printer. Ultrasonic vibration was applied on both sides of the specimens in two different modes. Surface roughness and thickness were measured before and after ultrasonic application. Tensile strength was measured post-ultrasonic application and compared with the control specimens. For internal detail observation, X-ray computed tomography (X-ray CT) was used. In all cases, surface roughness was reduced significantly on the specimens’ top surfaces post-ultrasonics. The thicknesses were not significantly changed. The mean maximum tensile strength increased for all sets of specimens’ post-ultrasonics. X-ray CT images showed that post-ultrasonic specimens had fewer voids compared to the control specimens. Ultrasonic-generated heat and downforce might have facilitated combined squeeze flow and intermolecular diffusion between the successive layers of deposited plastics to increase interfacial healing.

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