Masters Theses

Orcid ID

https://orcid.org/0009-0001-9928-3287

Date of Award

8-2023

Degree Type

Thesis

Degree Name

Master of Science

Major

Mechanical Engineering

Major Professor

Tony L. Schmitz

Committee Members

Jared Bradley, Uday Vaidya

Abstract

The modern world would not be what it is now without machine tools. Advances in materials and processes, such as carbon fiber and additive manufacturing (AM), enable the design space for machine tool components to expand. However, machine tool components require accurate geometry, which is not available from parts produced by metal Big Area Additive Manufacturing (mBAAM). This project outlines the process in which a traditionally manufactured machine tool component, a welded box structure on an existing machine tool, was redesigned to be made using mBAAM. The goal was to design a structure that was printable using the MedUSA system at Oak Ridge National Laboratory (ORNL) and measure the dynamic characteristics of the printed part using modal testing for comparison to finite element models.

The MedUSA system consists of three robotic arms that each manipulate a gas metal arc welding (GMAW) torch. The three torches were used to simultaneously deposit the mBAAM replacement for the traditional welded box structure. The print continued for 245 layers before it was stopped due to significant distortion caused by thermal deformation and fixturing failure. However, modal testing was completed on the 77\% complete structure to compare with finite element models that simulated bending mode shapes and natural frequencies. It was confirmed that the printed structure dynamics agreed with the numerical model predictions, which demonstrated that it is feasible to model a large-scale mBAAM part and understand its behavior prior to printing. Another significant outcome of this study is that the incomplete print shows that there remains a knowledge gap for successful mBAAM. The outcome of this project adds to the understanding necessary to enable successful large metal prints in the future.

AM has become a popular technology due to its expanded opportunities for unique geometries and wide design space, but challenges remain. This printed structure, although incomplete, demonstrates ongoing issues with thermal management and residual stress in large parts. Overall, this study demonstrates an example of designing and printing a large-scale metal structure that was validated through modal testing.

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