The Rheological Property of Composite Filament Material in the Material Extrusion Process

Abstract

Composite material extrusion (CME) additive manufacturing technique has great development potential and application advantages in astronautics and aerospace, health care, and industrial design due to its advantages of low cost, high material utilization, and so on. In the green part shaping process, the rheological property parameters of the molten filament are key factors affecting the forming process and quality. However, the corresponding research is still in the beginning stage, and the specific influences and conditions of material formability are still unclear. In this study, three different high-filling-ratio self-made 17-4PH stainless steel powder/polymer composite filaments were studied with material extrusion equipment to analyze their formability conditions. The pressure drop of the molten composite material during the shaping process was then measured by the self-constructed experimental platform, and the results of the relevant rheological properties were analyzed. Subsequently, an analytical rheological model of the molten material was established, and the theoretical analysis on the parameters was performed. Finally, a sensitivity analysis was carried out on the analytical model to investigate the influence of nozzle diameter, building speed, and extrusion temperature on the rheological property of the molten filament material. The results show that the self-made composite filament can be used to fabricate good-quality green samples. The theoretical model was verified to be reliable through the comparison between predictions and measurements (the error range is 7.07−8.1%), and the mechanism of the rheological property was elucidated. The rheological property parameters of the molten material gradually increase with the increasing filling ratio of the metal powder. Within the discussed parameter range (0.4–0.8 mm nozzle diameter, 240–260°C extrusion temperature, and 10–20 mm/s building speed), the nozzle diameter has the most significant effect on the rheological property of the molten material, followed by the building speed, while the effect of extrusion temperature is relatively weak.