Influence of layer height and nozzle diameter on the resistivity of additively manufactured electrically conductive structures made by material extrusion

Purpose This study aims to investigate how nozzle diameter and layer height influence electrical resistivity and surface roughness in conductive structures fabricated via material extrusion (MEX). The goal is to optimize process parameters for improved electrical properties in Additive Manufacturing. Design/methodology/approach A systematic experimental study was conducted using single-layer rectangular specimens fabricated by MEX with an electrically conductive composite made of Polylactic Acid with carbon nanotubes (PLA/CNT). Nozzle diameters were varied in six increments, and layer heights adjusted in 50 µm steps within process limits. Resistance measurements were performed with the four-wire technique and surface roughness was evaluated using an optical profilometer. Statistical analyses were used to assess the impact of these parameters on resistivity and roughness. Findings The results demonstrate a significant influence of nozzle diameter and layer height on resistivity and surface roughness. An optimal layer height-to-nozzle diameter ratio of 40–60% minimized resistivity. Deviations from this range led to disrupted conductive networks or reduced inter-strand contact. Higher surface roughness correlated with a reduced conductive cross-section, further impairing electrical performance. Research limitations/implications This study is limited to single-layer specimens and a single material type (PLA/CNT composite). Future research should address multi-layer components and alternative composite formulations to validate and extend the findings. Practical implications The findings offer practical guidelines for optimizing MEX process parameters to improve electrical conductivity and overall performance of printed components. Originality/value This paper addresses a gap in understanding the combined effects of nozzle diameter and layer height on resistivity and surface roughness. The findings provide valuable insights for product developers to optimize electrical performance while balancing manufacturing efficiency.