This article analyzes temperature fields and their variations in fused filament fabrication (FFF) from the filament entering the hot-end to the printed parts, aiming at a deeper understanding of the thermal process of this additive manufacturing technology. A standard E3D print head assembly was mounted on a robot arm for printing. A stable filament feeding region was determined with an upper limit in the volume flow rate at different nozzle temperatures. Within the limit, the steady-state temperature fields inside the hot-end were studied by a computational fluid dynamics model. Simulations indicated that the temperature became less homogeneous at higher flow rates, leading to a lower extrudate temperature at the nozzle outlet. These outlet temperatures were analyzed, validated, and used as input to simulate temperature variations in printed parts with a self-developed open-access numerical model. An interlayer time similarity rule was found in printing single-walled geometries, which specifies temperature similarities at the same interlayer time. The findings provide new insights into FFF processes, pointing out opportunities for improved production efficiency and scalability to large-scale manufacturing.

Temperature fields and their variations in printed parts are the basis for understanding the physical process of fused filament fabrication (FFF). However, reliable temperature data are still rather limited to date. This article presents a three-dimensional transient-state model to simulate the temporal and spatial temperature variations in FFF printed parts. Model variables range from geometry dimensions and (dynamic) material properties to process parameters, covering all important physical phenomena, including conduction anisotropy and radiant heat transfer. The validation of the model is performed against six sets of experimental temperature data obtained with different geometries, machines, materials, processes, temperature measuring methods, etc. Insights in the thermal process are also reported. For example, the heat penetration depth in printing with poly(lactic acid) is limited to 3 mm, and the Biot number intimately characterises the reheating peaks in temporal profiles. This model shows the potential to become a standardised tool to study the thermal characteristics of FFF printed parts. It is made openly available on website https://iiw.kuleuven.be/onderzoek/aml/technologyoffer. Graphic abstract