Closed-Loop Filament Feed Control in Fused Filament Fabrication

Filament Transport Control for Enhancing Mechanical Properties of Parts Realised by Fused Filament Fabrication

“…To evaluate the slippage influence on mechanical properties of FFF parts, an experimental campaign was conducted using different values of fabrication feed rate and a closed-loop system capable of compensating slippage. In this way, the correct extrudate flow rate was ensured [ 12 ]. A FFF prototype machine [ 34 ] was used to fabricate both specimens suitable for tensile tests [ 35 ] and dynamic mechanical analysis (DMA) [ 36 ].…”

“…Several works presented in the literature analysed the correlation between mechanical properties and process parameters. It was demonstrated that an increase in the fabrication feed rate causes slippage between filament and the feeding system [ 10 ], which leads to a decrease in the extruded material flow [ 11 ], and thus in part density [ 12 , 13 ].…”

“…These latter affect both contact pressure and extrusion pressure [ 33 ], which in turn modify the compression force acting on the filament and hence may cause slippage. Moreover, mechanical and rheological properties of filament also affect the extrusion pressure, and thus slippage [ 12 ], making the trial-and-error approach aimed at identifying the best flow% value challenging and time-consuming. To overcome such limitations, different closed-loop control systems have been implemented with the aim of controlling the material flow exiting the cold end.…”

“…To overcome such limitations, different closed-loop control systems have been implemented with the aim of controlling the material flow exiting the cold end. In [ 13 ], the author has proposed a closed-loop system for filament transport based on imaging, while in [ 12 ] the nominal transport of the filament exiting the cold end has been corrected using the value measured with an optical encoder. The last-mentioned closed-loop system acts continuously on the filament feed rate to achieve a minimum difference between the measured transport and the nominal one, as defined in the part program, regardless of process parameters and deposition conditions.…”

“…The last-mentioned closed-loop system acts continuously on the filament feed rate to achieve a minimum difference between the measured transport and the nominal one, as defined in the part program, regardless of process parameters and deposition conditions. Results reported in [ 12 ] have shown an increase in the part density as a consequence of the reduction of voids inside the part, and thus an increase of contact regions between deposited strands, both intra- and inter-layer. As slippage is a well-known issue in the literature and it has been proven how it may cause under-extrusion during the process, this work aims to quantitatively investigate its effect on the mechanical properties of FFF parts.…”