Date of Award
2026-05-01
Degree Name
Doctor of Philosophy
Department
Mechanical Engineering
Advisor(s)
Ryan B. Wicker
Second Advisor
Francisco Medina
Abstract
Laser Powder Bed Fusion technology offers unparalleled design freedom, reduced materials waste and the ability to produce near net-shape parts, which has led to its rapid adoption across various industries. However, as with other Additive Manufacturing processes, it is pervaded by high variability in part quality and part properties. This, in turn, negatively impacts its reliability and predictability, making it less appealing to manufacturers and preventing its implementation for the fabrication of critical, high-performance components. The cause of the variability lies in the formation of defects during the build process, which directly affect the microstructure and, therefore, the quality and properties of the part. In this case, the term "defect" is used to describe anomalies or irregularities within the microstructure, which may or may not be considered as flaws depending on the criteria of a governing entity, such as a manufacturer. In the context of gas flow-induced irregularities, the present work considers these variations as defects and refers to them as such throughout the thesis. These defects are governed by process parameters, which can be classified into five main categories: scanner, laser, powder, temperature, and atmosphere. The last one, which refers to the subsystem in charge of maintaining an inert environment and a constant shielding gas flow across the chamber, has been the focus of numerous investigations aiming to identify the influence of gas flow over defect formation. The specific mechanics are well established in literature, and the correlation between the two is acknowledged by industry standards, with most of them underscoring the importance of flow field control and optimization. This reveals a gap in the field of Additive Manufacturing, where a standardized or recommended method for the study of gas flow does not appear to exist. Research groups have implemented numerous strategies to better understand flow distribution within Laser Powder Bed machines, nonetheless, the specific procedures are researcher-dependent and may vary between one machine and another. As such, the present work seeks to provide a reference framework for the study of gas flow. For the first step, modifications are made to a commercial system with a known region of recirculation with the objective of enhancing gas flow distribution. The effectiveness of these modifications is validated through the implementation of magnetic resonance velocimetry, which provides a detailed representation of the flow field. To understand the effect of this change to gas distribution over part quality, single-track plate scans are performed within the affected region. Observations reveal deeper melt pools with less variation, which can be attributed to the modification to chamber configuration. Further analysis suggests that the influence of shielding gas flow over spatially induced variations can be minimized, thus eliminating the flow subsystem as a potential factor for defect formation. Having demonstrated the correction of the flow field on a commercial system, enabled by the prior understanding of the flow distribution, the investigation recenters its efforts around the development of a robust system for the study of gas flow with minimally invasive implementation. Upon completion, the device is deployed into the commercial system to characterize its original flow characteristics, which are then compared to the magnetic resonance velocimetry observations for validation. Comparisons show good agreement between datasets, thus indicating the correct operation and reliability of the device. Subsequently, additional measurements are analyzed to identify dominant frequencies and characteristic lengths of flow structures, in an effort to relate process conditions to chamber geometry. Once done with the exploration of the original configuration of the commercial system, the investigation is repeated on the modified layout and the results are compared to one another. It is revealed that the correction of the flow field can be observed through the measurements obtained with the device, further demonstrating its capabilities for flow characterization. The new distribution, while more consistent, also exhibits a thinner flow layer at some locations, thus exposing some of the potential limitations of the design. Afterwards, the device is deployed into two additional commercial systems to expand sample size for a better understanding of shielding gas flow differences and similarities between machines. It becomes evident that these systems have a better distribution, in terms of flow layer size, velocity retention, and lower variability. As a result, an analysis is carried out in an attempt to relate flow layer characteristics to inlet nozzle design and geometry. It is determined that distance from the build plate to the vent is crucial in reducing inlet-induced variations and preventing regions of recirculation due to the presence of layer of separation. Likewise, it is concluded that taller inlet nozzles are beneficial for establishing a wide and cohesive flow layer throughout the chamber. Lastly, the feasibility of implementing this framework of study and the corresponding device are evaluated by considering strengths and limitations of the approach and comparing with industry needs and requirements.
Language
en
Provenance
Received from ProQuest
Copyright Date
2026-05
File Size
284 p.
File Format
application/pdf
Rights Holder
Hector Hugo Estrada Medinilla
Recommended Citation
Estrada Medinilla, Hector Hugo, "Development And Implementation Of A Measurement Framework For The Study Of Gas Flow Distribution Within Laser Powder Bed Fusion Systems" (2026). Open Access Theses & Dissertations. 4670.
https://scholarworks.utep.edu/open_etd/4670