Hardware Factors Influencing Interlayer Bonding Strength of Parts Obtained by Fused Filament Fabrication<strong></strong>

Abstract

Current paper investigates the influence of hardware setup and parameters of a 3D printing process based on fused filament fabrication (FFF) technology on resulting sample strength. Three-point bending of samples printed with long side oriented along Z axis was used as a measure of the interlayer bonding strength. The same CAD model was converted into NC-programs through same slicing software to be run on four different desktop FFF 3D printers, out of filament of same brand and color. Within all the printers same ranges of layer thickness values from 0.1 to 0.3 mm and feed rates from 25 to 75 mm/s were planned to be varied. All the machines demonstrated statistically almost identical values of maximum flexural strength, however the different machines exhibited maximum sample strength with different combinations of varied parameters. Among all the hardware factors observed, the most important was proved to be extruder type, direct or Bowden. This feature fundamentally changes the nature of studied parameters influence onto the resulting strength of the FFF process. For the extruders of Bowden type the length of flexible guiding tube is of great importance.All the machines demonstrated statistically almost identical values of maximum flexural strength, however the different machines exhibited maximum sample strength with different combinations of varied parameters. Among all the hardware factors observed, the most important was proved to be extruder type, direct or Bowden. This feature fundamentally changes the nature of studied parameters influence onto the resulting strength of the FFF process. For the extruders of Bowden type the length of flexible guiding tube is of great importance.

Desktop Fabrication of Strong Poly (Lactic Acid) Parts: FFF Process Parameters Tuning

“…A turquoise PLA filament of 2.85 mm in diameter was used, produced by REC Company (Moscow, Russia). This specific manufacturer of filament was chosen due to locally produced material and the desire to obtain results comparable with previous studies [61,62,63,64].…”

“…Extrusion efficiency is defined as the ratio of the actual part mass to the calculated from models. The extrusion efficiency seems to be very dependent on hardware [63], but within single hardware configuration, it also depends on the melted polymer viscosity (which in turn depends on extrusion temperature) and the flow rate.…”

Desktop Fabrication of Strong Poly (Lactic Acid) Parts: FFF Process Parameters Tuning

“…A turquoise PLA filament of 2.85 mm in diameter was used, produced by REC company (Moscow, Russia). This specific manufacturer of filament was chosen due to locally produced material and the desire to obtain results comparable with previous studies [58][59][60][61].…”

“…The actual volume of material squeezed out by the correctly set up printer with a Bowden extruder (e.g. Ultimaker 2) through the nozzle per unit of time is always less than the calculated one: the slicer does not take into account the extrusion resistance [60]. As shown in [59], even printing with plastic overheated to 250 °C at low speed (2.2 mm3/s) resulted in extrusion efficiency equal just to 0.96.…”

“…Extrusion efficiency is defined as the ratio of the actual part mass to the calculated. The extrusion efficiency seems to be very dependent on hardware [60], but within single hardware configuration, it also depends on the melted polymer viscosity (which in turn is depends on extrusion temperature) and the flow rate.…”