Date of Graduation

5-2025

Document Type

Thesis

Degree Name

Bachelor of Science in Mechanical Engineering

Degree Level

Undergraduate

Department

Mechanical Engineering

Advisor/Mentor

Hu, Han

Committee Member

Shou, Wan

Abstract

This study served as an exploration into the possible existence of a correlation between the infill lattice structure of a 3D printed wall section and the thermal performance of that sample as characterized by thermal conductivity measured in units of Watts per meter Kelvin. With the continual increase in the practicality, fidelity, and applicable fields of additive manufacturing, namely FDM 3D printing, research on specific print characteristics and their effects on the material and thermal characteristics of the part in question is steadily becoming more commonplace. Although the thermal conductivity of 3D printed wall sections as a function of infill density in various structures has been previously characterized, the effects of the variation of those infill structures has not. This study aimed to potentially characterize the thermal performance of 3D printed wall sections as it relates to the infill lattice structure which is selected during the slicing stage of FDM additive manufacturing. In order to accomplish this, 3 different infill structures were selected and 3 thicknesses of each was manufactured using a BambuLabs P1S 3D printer. The thermal conductivity of these samples was tested using a setup based on the ASTM D5470 standard. This standard utilizes the assumptions of steady-state, one-dimensional heat conduction and uses Fourier’s Law for data analysis. Temperature gradients are measured across conductive metal meter bars with a sample sandwiched between. These gradients are extrapolated to calculate sample surface temperatures, which can be used to find the thermal conductivity of the sample in conjunction with the calculated heat flux through the meter bars. This standard is applicable for elastic materials that do not experience significant deformations under loads, such as most standard 3D printing filaments. The expected range of conductivities for the samples was 0.14-0.21 W/m*K, and the resulting range calculated from the data acquired during testing was 0.220-0.402. The results did indicate that the conductivities of the samples printed with Archimedean Chord infill were generally increased compared to the baseline. To verify this, a single factor ANOVA test was performed, which examines the discrepancies between multiple groups of data and compares it to the discrepancies within the data points of the groups themselves. If the differences between the groups are large compared to the intragroup differences, then the differences are declared statistically significant. This significance is measured by a P value and is satisfied if the value is less than 0.05. The results of this study generated a P value of 0.27, which indicates that the potential correlation is likely the result of simple probability rather than the effects of the independent variable (infill lattice structure). Nevertheless, this study does serve as a sound foundation for the development of more accurate and advanced procedures for exploring this relationship. More testing is absolutely required to verify or disprove this relationship, and continued efforts towards these findings will only advance the body of knowledge on additive manufacturing as a whole.

Keywords

3D Printing; Thermal Conductivity; Manufacturing; Infill

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