Bond formation between polymer filaments in fused deposition modeling process

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This research investigates the bond formation among extruded acrylonitrile butadiene styrene filaments in the fused deposition modeling (FDM) process. This phenomenon is thermally driven and ultimately determines the integrity and mechanical properties of the resultant prototypes. The bond quality was assessed in terms of changes in the mesostructure and the degree of healing achieved at the interfaces between the adjoining polymer filaments. Experimental measurements of the temperature profiles were carried out for specimens produced under different processing conditions. The effects of processing conditions on the mesostructures and mechanical properties (flexural strength) were also examined. Our results showed that the fabrication strategy, the envelope temperature and variations in the convection coefficient have strong effects on the cooling temperature profile, as well as on the mesostructure and the bond strength achieved between filaments. Parallel to the experimental work, predictions of the degree of bonding achieved during the filament deposition process were made based on a thermal analysis of extruded polymer filaments. The bond development between filaments was modeled using a Newtonian sintering and a non-isothermal molecular diffusion models. The sintering phenomenon was found to have a significant effect on bond formation, but only for the very short duration when the filament's temperature is above the critical sintering temperature. Otherwise, creep deformation was found to dominate changes in the mesostructure. The non-isothermal molecular diffusion model predictions were found to be very sensitive to changes in the temperature and estimated values for the welding time. Further work on the thermal analysis as well as for obtaining the welding time is needed to give accurate predictions of the degree of healing and bond strength achieved between polymer filaments that constitute FDM parts.
Bibliography: p. 107-121
Sun, Q. (2005). Bond formation between polymer filaments in fused deposition modeling process (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from doi:10.11575/PRISM/22992