Influence of Process Parameters in Material Extrusion on Product Properties Using the Example of the Electrical Resistivity of Conductive Polymer Composites

Abstract

Additive manufacturing of components using the material extrusion (MEX) of thermoplastics enables the integration of multiple materials into a single part. This can include functional structures, such as electrically conductive ones. The resulting functional structure properties depend on the process parameters along the entire manufacturing chain. The aim of this investigation is to determine the influence of process parameters in filament production and additive manufacturing on resistivity. Filament is produced from a commercially available composite of polylactide (PLA) with carbon nanotubes (CNT) and carbon black (CB), while the temperature profile and screw speed were varied. MEX specimens were produced using a full-factorial variation in extrusion temperature, layer height and deposition speed from the most and least conductive in-house-produced filament and the commercially available filament from the same composite. The results show that the temperature profile during filament production influences the resistivity. The commercially available filament has a lower conductivity than the in-house-produced filament, even though the starting feedstock is the same. The process parameters during filament production are the main factors influencing the resistivity of an additively manufactured structure. The MEX process parameters have a minimal influence on the resistivity of the used PLA/CNT/CB composite.

Influence of Manufacturing Process on the Conductivity of Material Extrusion Components: A Comparison between Filament- and Granule-Based Processes

“…The study used commercially sourced granules and filaments from FILOALFA ® . This compound consists of PLA filled with CNTs, as stated by the manufacturer, along with undisclosed amounts of carbon black and graphite [ 4 , 23 , 24 ]. Contreras-Naranjo et al discovered a fraction of MWCNT of approximately 3% of weight, with a CNT/CB ratio of 1:10 [ 24 ].…”

“…MEX structures exhibit anisotropic electrical properties due to the strand-by-strand and layer-by-layer nature of the manufacturing process. Therefore, the measurement method specified in DIN EN ISO 3915:2022-5 was modified, as described by Nowka et al [ 4 , 31 ]. The thickness of the sample was limited to one layer and its length was shortened to 60 mm to fit onto a microscope slide, preventing deformation during handling.…”

“…Due to the reduced length, the distances between the electrodes were altered. Nevertheless, the high conductivity of the material ensured that ISO 3915:2002-5 was still valid within its range [ 4 , 31 ]. For each specimen, the thickness was measured at three points using a QuantuMike ® 293-140-30 micrometer screw (Mitutoyo Corporation, Kawasaki, Japan).…”

“…It has been shown that the process parameters used to produce filaments significantly affect the conductivity of both the filaments and the subsequently manufactured MEX structures [ 4 ].…”

“…The resistivity of the filament MEX process has been extensively studied with respect to the influence of most process parameters [ 10 , 11 ]. Studies have often used commercially available filaments [ 4 , 10 , 11 , 18 , 20 ]. In contrast, the granule MEX process has only been used to process custom-made conductive polymer composites.…”