Date of Award

2022-05-01

Degree Name

Master of Science

Department

Mechanical Engineering

Advisor(s)

David Espalin

Abstract

Additive Manufacturing (AM) has experienced consistent growth since its inception across its seven process categories, especially Material Extrusion (MEX) with systems that can be seen in commercial and industrial settings. As MEX evolves, innovation can be traced in the growing variety of available process materials and new system capabilities leading to greater interest in the technology across various industries including automotive, aerospace and even nuclear weapons. This has created an increasing demand for end-use parts from MEX systems leading to more complex machines with additional Degrees of Freedom (DoF), specialized workflows, and expanded post processing that address the drawbacks of MEX and AM in general. Such drawbacks include material waste, long build times, poor surface quality, and porosity that leads to anisotropic properties, all of which limit the ability of MEX to produce certifiable end-use parts. Other manufacturing processes such as machining have also been incorporated into the MEX workflow as a solution to some of the issues previously mentioned, most notably to resolve poor surface quality. Additionally, efforts have been made to enhance the capability of MEX parts with embedded electronics and components which add part functionality beyond just simple structural or modeling applications. In the past, MEX has largely been an automated process where a user inputs an STL file and process parameters into a slicing software which then automatically slices and generates toolpaths or instructions, often in the form of G-Code for a machine to follow to build the part. Generally, little user intervention is required both during the slicing and building, moreover, to make any sort of change is a challenging task that requires technical knowledge in AM, G-Code, and automation. Multi-axis capabilities, a relatively new development in MEX AM, has seen a push for automated slicing and manufacturing, however, the additional DoF from a simple 3-axis cartesian system completely changes the nature of MEX and still requires significant amount of research to fully utilize its potential. This research focuses on exploring the realm of multi-axis MEX to provide a basis for future automation that fully utilizes the potential offered by additional DoF. For this research, a 5-axis gantry style machine with a tilting table and rotating platter is used to investigate the dynamics of multi-axis MEX with a focus on the deposited polymer material at the strand scale. Cross-sectional morphology of individual and grouped strands deposited at different angles was examined where porosity was not eliminated, however, strand morphology was impacted. Additionally, it was found that the outer geometry of the nozzle begins to interact with the deposited material when printing at an angle. The effect of angled deposition on the mechanical properties of printed parts was also investigated. The average UTS of standard XY samples (traditionally printed with nozzle orthogonal to build platform) was 41.6 MPa, which withstood 12% more stress compared to angled XY specimens. On the other hand, ZY specimens printed at an angle were able to withstand 14% more stress compared to their standard counterparts. Furthermore, the gap in UTS when comparing XY samples to ZY samples was reduced from 47% to 31%.

Language

en

Provenance

Received from ProQuest

File Size

101 p.

File Format

application/pdf

Rights Holder

Angel Vega

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