Investigation of the melt and flow behavior in the hot-end of a 3D printer using X-ray computed tomography

Additive manufacturing is a relatively new manufacturing technology known primarily for its nearly boundless design capabilities. Initially used for rapid prototyping and smaller quantities, the various processes have undergone improvements marking initial steps toward serial production. Fused filament fabrication (FFF), also termed fused deposition modeling (FDM) stands out as one of the most commonly employed additive manufacturing methods utilizing plastic filaments. As with other manufacturing processes, modeling and simulation of the process is the key to optimize the process in terms of minimizing waste and increasing production rates. A major interest is to better understand and simulate the melt and flow behavior within the hot-end. To address this, an experimental setup was developed at the Institut für Kunststofftechnik, aiming to provide insights into the melt and flow behavior within FFF printing nozzle during extrusion. This setup, coupled with X-ray computed tomography (CT) and radiographic testing, unveiled the forming melt profile within the melt channel during extrusion - a first-time visualization using X-rays. To increase the contrast, a hot-end with an integrated nozzle was engineered from aluminum and a polystyrene (PS) filament compounded with tungsten particles was employed. Feeding the modified filament at varying extrusion speeds enabled the examination of velocity profiles in the transmission setup. Utilizing this method, the understanding of material extrusion in 3D printing processes can be improved, simulations can be validated and potentially facilitates the future development of nozzle geometries adapted to extrusion speeds. © 2024-by the Authors.