Author ORCID Identifier

https://orcid.org/0000-0002-5328-4882

Year of Publication

2019

Degree Name

Master of Science in Mechanical Engineering (MSME)

Document Type

Master's Thesis

College

Engineering

Department

Mechanical Engineering

First Advisor

Dr. Y. Charles Lu

Abstract

3D printing is a revolutionary manufacturing method that allows the productions of engineering parts almost directly from modeling software on a computer. With 3D printing technology, future manufacturing could become vastly efficient. However, it is observed that the procedures used in 3D printing differ substantially among the printers and from those used in conventional manufacturing. In this thesis, the mechanical properties of engineering products fabricated by 3D printing were comprehensively evaluated and then compared with those made by conventional manufacturing. Three open-source 3D printers, i.e., the Flash Forge Dreamer, the Tevo Tornado, and the Prusa, were used to fabricate the identical parts out of the same material (acrylonitrile butadiene styrene). The parts were printed at various positions on the printer platforms and then tested in bending. Results indicate that there exist substantial differences in mechanical responses among the parts by different 3D printers. Specimens from the Prusa printer exhibit the best elastic properties while specimens from the Flash Forge printer exhibit the greatest post-yield responses. There further exist noticeable variations in mechanical properties among the parts that were fabricated by the same printer. Depending on the positions that the parts were placed on a printer platform, the properties of resultant parts can vary greatly. For comparison, identical parts were fabricated using a conventional manufacturing method, i.e., compression molding. Results show that compression molded parts exhibit more robust and more homogeneous properties than those from 3D printing. During 3D printing, the machine code (e.g., the Gcode) would provide the processing instructions (the x, y, and z coordinates and the linear movements) to the printer head to construct the physical parts. Often times the default processing instructions used by commercial 3D printers may not yield the optimal mechanical properties of the parts. In the second part of this thesis, the orientation-dependent properties of 3D printed parts were examined. The multi-layered composite theory was used to design the directions of printing so that the properties of 3D printed objects can be optimized. Such method can potentially be used to design and optimize the 3D printing of complex engineering products. In the last part of this thesis, the printing process of an actual automobile A-pillar structure was designed and optimized. The finite element software (ANSYS) was used to design and optimize the filament orientations of the A-pillar. Actual parts from the proposed designs were fabricated using 3D printer and then tested. Consistent results have been observed between computational designs and experimental testing. It is recommended that the filament orientations in 3D-printing be “designed” or “tailored” by using laminate composite theory. The method would allow 3D printers to produce parts with optimal microstructure and mechanical properties to better satisfy the specific needs.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2019.418

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