Dissertation

Evaluation of Ultrasonic Energy Augmented Fused Deposition Modeling of Polylactic Acid Specimens

Quader, Raihan

2025

Overview

FDM is the most widely used AM process due to its ability to fabricate complex geometries at a lower cost. However, its process characteristics introduce anisotropy in the Z-direction due to interlayer voids and result in a stepped surface finish. Global research efforts are addressing these limitations through techniques such as infrared pre-heating, plasma heating, localized laser heating, and ultrasonic vibration, with the latter not investigated in the way this dissertation explores. The effect of applying ultrasonic vibration in FDM through three distinct approaches by focusing on interlayer voids, surface finish, and dimensional accuracy has been investigated thoroughly in this study. The study utilizes PLA as the material of interest and employs mechanical property testing, X-ray CT, SEM, and other physical characterization methods. In the first approach, ultrasonic vibration was applied to both sides of completed FDM parts as a post-processing technique. This method reduced surface roughness by up to 70%, decreased thickness by 5.2%, and increased tensile strength by 15.31%. The second approach was an in-situ procedure where printing was repeatedly paused after every few layers, and ultrasonic vibration was applied on the whole layer of material in a scanning mode. Impact resistance of the parts increased by 54% as a result, but the tensile strength was mostly unaffected. In the final approach, the printing was repeatedly paused, similar to the previous approach, but an image processing method was implemented to identify the part’s contour shape and position on the bed. Further processing of the image was done to generate tool paths inside the contour. Following the distance calculation of the tool paths from the home position of the ultrasonic horn, the ultrasonic vibration was applied in a contour scanning mode on different layers. This approach resulted in a 36% increase in maximum tensile strength and a 73% improvement in impact resistance. These findings highlight the potential of ultrasonic vibration in enhancing the mechanical properties and surface finish of FDM-printed parts from PLA. This hybrid approach will increase the usage of PLA in high-strength applications. Improvements are in progress to develop an industry-friendly hybrid FDM system.

• Publisher: ProQuest Dissertations & Theses
• Subject: Engineering / Industrial engineering / Mechanical engineering / Medical imaging
• ISBN: 9798293819508