In Situ Process Characterization and State Assessment in FFF Using Pitch-Catch Techniques

Fused Filament Fabrication (FFF) stands out due to its simple operating principle, low production cost, and wide range of available materials. However, the inherent anisotropy of thermoplastics frequently leads to interlinear void formation during deposition, compromising the mechanical properties of printed parts. Currently, the lack of effective in situ monitoring methods for the spatial localization of defects restricts the widespread adoption of FFF in industrial applications. As an alternative, vibration-assisted inspection has gained recognition as a developing non-invasive technique for process data acquisition. To improve knowledge to this topic, this study proposes extracting dynamic characteristic curves from objects constructed via FFF. The proposed methodology involves introducing two identical electrodynamic transducers in a pitch-catch configuration, where one transducer acts as an emitter and the other as a receiver, both integrated into the printer's heated bed. The energy propagating through the bed reflects the vibration signals of the part under construction, which are collected by the receiver transducer. The results present a novel methodology to locate structural damage indicators during object fabrication by characterizing the médium, the heated bed and, consequently, the printed part itself. Thus, it was possible to identify the highest-magnitude bands and, based on them, generate acoustic maps that detect potential anomalies during the process.