Empirical Study of In-Plane Shrinkage and Bulging of Circular Cylinders Fabricated with the Fused Deposition Modeling Additive Manufacturing Method
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This thesis presents a set of empirical studies, leading to three Design for Additive Manufacturing (DfAM) tools for estimating diametric shrinkage and the longitudinal variation of diameter in circular cylinders produced by the Fused-Deposition Modeling (FDM) method. First, four experiments are conducted by additively printing 50 cylinders and taking 1900 measurements in order to study the variation of diametric shrinkage along the cylinder axis and the variation of shrinkage as functions of four parameters of the cylinder: top and bottom thicknesses, diameter, height, and shell thickness. These four subjects of study are addressed as five research questions and are answered by testing a total of seven statistical hypotheses. The variation of in-plane shrinkage along the axis produced an interesting bulging effect, which is also studied. The studies are conducted using a custom-made, dual-extrusion, 3d-printer and a polylactic acid plastic (PLA). Then, the statistically significant trends from the experiment are compiled to form three DfAM tools, presented as charts, which could be used to estimate and compensate for shrinkage and bulging in FDM-printed circular cylinders of sizes comparable to those used in the study.