Highlights on the Influence of Thermal Reprocessing of PLA on Mechanical Properties

FDM is one of the most popular additive manufacturing techniques through 3D printing. Within this technique, one of the intensively studied subjects is the analysis of the factors that influence the mechanical behavior of the 3D printed parts. However, despite numerous studies that show the influence of parameters such as raster orientation, layer height/thickness, build orientation, number of layers, there are some other process parameters which are less analyzed. Due to some interactions between the effects due to different parameters, it becomes challenging to analyze influences on the mechanical behavior of 3D printed materials. Less studied subject is the mechanical behavior of the extruded filament through the nozzle and the interaction between deposited traces. The mechanical behavior of the air extruded filament, the one trace, two traces and fourteen traces deposition were experimentally analyzed in the paper by tensile testing. Also, the mechanical behavior of the raw filament was checked. In addition, the differential scanning calorimetry (DSC) was conducted on raw filament and extruded filament in order to identify the relation between the crystallinity of the polymer after thermal reprocessing with the mechanical properties. The raw filament is typically a continuous and homogenous material with consistent diameter and structure. However, when the filament is extruded trough the nozzle its mechanical behavior will significantly change due to thermal reprocessing. Among the factors that influence the properties are: extruder temperature, platform temperature, extruding velocity, cooling, flow rate of the extruded filament. All can affect the crystallinity of the polymer on one hand and the strength of the adhesion between the consecutive traces on the other hand, as the results are quantifying it.