A comparative study of surface roughness, tensile strength, microstructure, and porosity of the un-dried and pre-dried PETGTPU FDM filaments

Bakrulazi, Siti Aishah (2022) A comparative study of surface roughness, tensile strength, microstructure, and porosity of the un-dried and pre-dried PETGTPU FDM filaments. Project Report. Universiti Teknikal Malaysia Melaka, Melaka, Malaysia. (Submitted)

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Abstract

PETG and TPU filament are hygroscopic, causing bubbles and poor printing quality in 3D printed parts. Drying the filament before printing may remove moisture and improve surface quality, restoring its original performance and preventing pores. The effect of humidity on the quality of 3D printing is less explored. Moisture can alter the tensile strength and surface topography by causing roughness and porosity of 3D printed parts. This study used ANOVA to analyse the surface roughness of 3D printed PETG and TPU parts. Pre-dried samples have a smoother surface than un-dried samples. TPU is rougher than PETG because has higher surface roughness. This study measured the tensile strength of pre-dried 3D printed PETG and TPU parts using a Universal Testing Machine and found they are stronger than un-dried samples. Tensile strength increased with drying. This study evaluates the cross-sectional microstructure of fractured 3D printed parts using SEM. Un-dried samples have larger interlayer gaps, inter-bead pores, and an incomplete diffusion pattern due to dampness. Pre-dried sample had fewer inter-bead pores and interlayer gaps. PETG has less interlayer gaps than TPU. This study also used the Archimedes Principle to measure the porosity of 3D printed PETG and TPU pieces. Un-dried samples are more porous than pre-dried samples due to the density difference between PETG and TPU. Un-dried samples are porous and less dense. TPU is permeable and it is less dense than PETG. In order to do so, three conditional settings were established; (i) a new PETG and TPU roll acts as the reference, (ii) used PETG and TPU roll stored in the vacuum bag with silica gel for 50 grams, and (iii) used PETG and TPU roll stored in an open environment, exposed with the humidifier for 48 hours, 96 hours and 150 hours. This paper presents the first comprehensive investigation on evaluation of surface roughness, tensile strength, microstructure, and porosity of the pre-drying humidified PETG/TPU FDM filament. As a result, the drying method is improving the tensile strength, surface roughness and surface topography, as well as reduce the porosity of the 3D printed parts. Further research is needed on FTIR analysis, which can analyse the chemical composition of micro and nanoscale particles, and compress tests, which can identify the modulus of elasticity, proportional limit, compressive yield point, compressive yield strength, and compressive strength.

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