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An Automated shrinkage compensation method for the holes fabricated via FFF process

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2019
Vayghannezhad, Sardar
This thesis presents an automated shrinkage compensation algorithm for 2.5D specimens to be fabricated via Fused Filament Fabrication process. The algorithm operates on a closed curve representing the hole of a 2.5D specimen, and generates a corresponding compensation structure regardless of the hole’s geometric characteristics. Accordingly, this thesis initiates with introducing a viscoelastic model that would reproduce the behavior of the PLA filament from the time of extrusion onto the build plate until it is cooled down to room temperature. Based on the viscoelastic model and corresponding mathematical equations, a final strain associated with a 2.5D structure having a central hole is calculated. Finally, to empirically verify the theory behind this work, three types of tests are designed and conducted. Two of these tests are seek to check the validity of the strain rate already obtained, on specimens without bridge lines. The third test setting, however, brings into play the positive effect that bridge lines have on the shrinkage of the central opening.