Date of Award

5-11-2018

Publication Type

Doctoral Thesis

Degree Name

Ph.D.

Department

Industrial and Manufacturing Systems Engineering

Keywords

Additive Manufacturing, Material Extrusion Process, Optimization, Plastic, Toolpath, Voids

Supervisor

Ruth Jill Urbanic

Rights

info:eu-repo/semantics/openAccess

Abstract

A problem with the planning solutions for the additive manufacturing material extrusion process is a lack of optimization strategies to improve upon the standard raster and contour toolpaths. After experimental testing, it was recognized that a component’s strength relationship with respect to the volume of material usage is inconsistent and that failures occurred in regions of voids. From previous studies, it was found that a build orientation in the material extrusion process influences the support material requirements, processing time, surface finish, voids volume, etc. This dissertation aims to identify, minimize, and manage void regions during the toolpath generation, and studies the effects of build orientation on the amount and location of unwanted voids in the finished part. This includes comparing all possible build orientations to minimize voids in each layer, preventing void regions from being stacked in 3D, and avoiding creating an internal chimney. This approach is divided into three phases. Phase I is minimizing voids in each layer, phase II is identifying and managing voids between layers, and the third phase is comparing the total voids in all possible build orientations. Material extrusion processes, with a wide selection of nozzle sizes (0.4 mm to 21 mm), are considered suitable candidates for this solution. To carry out this study, a literature review was performed to understand the influence of the build parameters. Then, an analysis of valid parameter settings to be targeted was performed on a commercial system. The mathematical model is established based on the component geometry and the available build options for a given machine-material configuration. A C++ program has been developed to select a set of standard (available) toolpath parameters to determine the optimal output process variables (bead width, raster angle, and the overlap percentage), managing voids between layers, and compare total voids in all possible build orientations. Case studies are presented to show the merits of this approach. It is found that the entire void area is significantly reduced (~7%) with the phase I, by 5% with the second phase, at least 11% with phase III.

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