Identification and standardisation of parameters to improve the understanding of mechanical properties of FFF/FDM/MEX parts

Abstract

Fused Deposition Modelling (FDM)/Fused Filament Fabrication (FFF)/Material Extrusion (MEX) is a well-known Additive Manufacturing (AM) process used in various fields of production. The extrusion/printing speed, nozzle temperature and build plate/bed temperature were determined through literature screening to be the printing parameters that have the greatest effect on the tensile strength of a printed specimen. These were used in a two-level fractional factorial design to obtain the Design of Experiments (DOE). The DOE was used during the development of a material evaluation guideline for the printing of polylactic acid (PLA) on open-source printers. All printers used Cura® as slicing software. Various filaments were used on different printer models. CRON PLA yielded the highest average Ultimate Tensile Strength (UTS), while Zortrax PLA resulted in the best repeatability between samples within one experiment. The Creality Ender-6 delivered consistent results irrespective of the type of filament used. The effect of printing and bed temperature on the UTS were significant for Wanhao PLA/Creality Ender-6. Printing temperature was significant for Buildvolume PLA/Creality Ender-6. Bed temperature, printing speed and the interaction between these parameters were significant for Flashforge PLA/Creality Ender-6 and Wanhao PLA/Creality Ender-3 Max. Printing temperature, bed temperature and printing speed had a significant effect on the UTS for Zortrax PLA/Creality Ender-6. There were no statistically significant effects for CRON PLA/Creality Ender-6, Wanhao PLA/Creality Ender-5 Plus and Wanhao PLA/Wanhao Duplicator 9 300. Printing speed was statistically significant for Wanhao PLA/Creality Ender-5. The effect of bed temperature and printing speed were significant on UTS for CRON PLA/Wanhao Duplicator 9 I3.