Graduate Studies, UNL
Embargoed Master's Theses
First Advisor
Qilin Guo
Committee Members
Jeffrey Shield, Bai Cui
Date of this Version
12-2025
Document Type
Thesis
Citation
A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science
Major: Mechanical Engineering and Applied Mechanics
Under the supervision of Professor Qilin Guo
Lincoln, Nebraska, December 2025
Abstract
Additive Manufacturing (AM) is emerging as an alternative to classical manufacturing techniques; it involves a layer wise building strategy to create 3D structures with either polymers or metals. Laser powder bed fusion falls within one of the seven main classifications of different AM techniques; it is the leading technique used worldwide in relation to the creation of AM metal structures. Copper is commonly used across several sectors in thermal management and electrical components such as cooling systems, heat exchangers, electrical wiring to name few due to its thermal and electrical properties such as thermal and electrical conductivities of 401 W/m·K and 5.96 × 107 S/m respectively. Generally, LPBF is conducted with the use of a Near Infrared (NIR) Laser of with wavelength range (1060–1080) nm, however copper reflects approximately 95% of light when irradiated with NIR lasers. Due to copper’s high thermal conductivity which results in rapid heat loss and high reflectance of NIR lasers has created multiple challenges in creating AM parts with high relative density. However, recent research has been focused on visible wavelength (400–700) nm lasers that can be absorbed at a higher percentage when copper is irradiated. Hence this research utilizes a blue wavelength (443 nm) laser to explore potential parameters that can be used to create copper structures with high relative density as well as intentionally porous copper structures as foundational proof of concept. A key component of the LPBF process is the scan strategy used to create 3D structures therefore, various forms of scan strategies including alternate layer 90° and 67° raster scan rotations were explored in this research as a method to analyze their effects on AM part quality. In addition, thermal management strategies such as beam wobbling and preheating were conducted to combat the reduction in melt pool dimension as the build height increased. This research was able to achieve up to 99% relative density for a copper AM part with the implementation of beam wobbling scan strategy. Furthermore, the findings and processing parameters explored in this research will add to the limited amount of literature related to AM copper printing with visible lasers which could provide more in-depth knowledge about processing highly thermally conductive materials.
Advisor: Qilin Guo
Comments
Copyright 2025, Terrol Wilson. Used by permission