Modeling raster bead deformation process for monitoring fused filament fabrication using acoustic emission

Abstract In the fused filament fabrication (FFF) deposition process, the filament material undergoes a complex process of thermal melting and reshaping. Macroscopic geometric accuracy and mechanical strength are the main concerns of the printed model by most researchers. However, there is limited research on the microscopic raster bead process, especially on its dynamic evolution, even though this is crucial for ensuring accuracy and strength. In addition, the online monitoring system for FFF processes is not well-developed, the quality of finished samples being mainly evaluated by their appearance. To fill up these gaps, this study focuses on the investigation of the microprocesses of FFF to gain in-depth understanding of raster bead evolution and its acoustic emission (AE) generation characteristics. A model of material extrusion was developed based on the wall jet impingement model. A finite element (FE) analysis revealed a mutual microscopic compression between different raster beads, in which the deformed edges compress subsequent raster beads, leading to different dynamic stresses. Experimental studies based on AE show that raster compression becomes more severe with the increase in infill density, while higher material temperature exacerbates raster compression, and faster printing speed increases compression stress. The FE simulation and experiments reveal the cumulative effects of compression in continuous printing. This study demonstrated that AE can be an effective method for online monitoring of the micro-deposition process of raster beads. In summary, this study introduces an AE-based method for monitoring the interactions between raster beads during the deposition process. The research explores a method for online monitoring of the micro-deposition process of raster beads, which has the potential to improve the geometric accuracy of FFF.