Date on Master's Thesis/Doctoral Dissertation

5-2021

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Mechanical Engineering

Degree Program

Mechanical Engineering, PhD

Committee Chair

Atre, Sundar V.

Committee Co-Chair (if applicable)

Kate, Kunal

Committee Member

Kate, Kunal

Committee Member

Berfield, Thomas

Committee Member

Grant, Gerald

Author's Keywords

Metal fused filament fabrication (MF3); FEA simulation; ti-6Al-4V alloy; design for additive manufacturing; lattice structure by additive manufacturing; maxillofacial implant by 3D printing

Abstract

Additive manufacturing (AM) offers unmatchable freedom of design with the ability to manufacture parts from a wide range of materials. The technology of producing three-dimensional parts by adding material layer-by-layer has become relevant in several areas for numerous industries not only for building visual and functional prototypes but also for small and medium series production. Among others, while metal AM technologies have been established as production method, their adoption has been limited by expensive equipment, anisotropy in part properties and safety concerns related to working with loose reactive metal powder. To address this challenge, the dissertation aims at developing the fundamental understanding required to print metal parts with bound metal powder filaments using an extrusion-based AM process, known as metal fused filament fabrication (MF3). MF3 of Ti-6Al-4V has been investigated, owing to significant interest in the material from aerospace and medical industries on account of their high strength-to-weight ratio, excellent corrosion resistance and biocompatibility. To investigate the material-geometry-process interrelationship in MF3 printing, the current work looks into the process modeling and simulation, the influence of material composition and resulting characteristics on printed part properties, effects of printing parameters and slicing strategies on part quality, and part design considerations for printability. The outcome of the work is expected to provide the basis of design for MF3 (DfMF3) that is essential to unlocking the full potential of additive manufacturing. Moreover, the layer-by-layer extrusion-based printing with the highly filled material involves several challenges associated with printability, distortion and dimensional variations, residual stresses, porosity, and complexity in dealing with support structures. Currently, a high dependency on experimental trial-and-error methods to address these challenges limits the scope and efficiency of investigations. Hence, the current work presents a framework of design for MF3 and evaluates a thermo-mechanical model for finite element simulation of the MF3 printing process for virtual analyses. The capability to estimate these outcomes allows optimization of the material composition, part design, and process parameters before getting on to the physical process, reducing time and cost. The quantitative influence of material properties on MF3 printed part quality in terms of part deformation and dimensional variations was estimated using the simulation platform and results were corroborated by experiments. Also, a systematic procedure for sensitivity analysis has been presented that identified the most significant input parameters in MF3 from the material, geometry and process variables, and their relative influence on the print process outcome. Moreover, feasible geometry and process window were identified for supportless printing of Ti-6Al-4V lattice structures using the MF3 process, and an analytical approach has been presented to estimate the extrudate deflection at the unsupported overhangs in lattice structures. Finally, the design and fabrication of Ti-6Al-4V maxillofacial implants using MF3 technology are reported for the first time confirming the feasibility to manufacture patient-specific implants by MF3. The outcome of the work is an enhanced understanding of material-geometry-process interrelationships in MF3 governing DfMF3 that will enable effective design and manufacturing.

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