Unobtrusive In Situ Diagnostics of Filament-Fed Material Extrusion Additive Manufacturing

Build defects, such as nozzle clogging and thermal substrate deformation, are common in material extrusion additive manufacturing technologies, and are difficult to detect because of the high-temperature environment of fused deposition modeling (FDM) machines that do not accommodate internal sensors. To overcome this difficulty, this paper integrated an external sensor to monitor the supply current of the motor that fed filament into an extrusion head. This paper describes the investigation of the relationship between the deposition status and the reaction torque on the filament-feed motor. A dynamic model of the internal operation of the FDM extrusion head was developed and used to infer printing defects. The change in reaction force opposing extrusion was indirectly measured by monitoring the current delivered to the filament-feed motor, and consequently, the use of other sensors in the high-temperature chamber was avoided. An analysis of the supply current, in both time and frequency domains, enabled the detection of defects during material deposition.