Numerical Analysis of a Rotating Die Roughness in a FDM Impregnation Process of Continuous Fibres

Additive manufacturing (AM) has been increasingly adopted for prototyping and small-scale production, and it is progressively replacing traditional manufacturing methods, such as injection moulding. Among AM techniques, fused deposition modelling (FDM) has a predominant role due to its flexibility, ease of use, and the relatively low cost of both materials and equipment. Particularly, the integration of continuous long fibres has marked a significant breakthrough in enhancing the performances and mechanical strength of printed components. This research focuses on an engineered extrusion system equipped with a die rotation mechanism and designed to produce pre-impregnated continuous fibres. The study considered how the rotating die’s surface roughness can affect the velocity field of the polymer matrix and, hence, the overall matrix-fibre impregnation process. In this context, in the developed CFD model several die with varying helicoidal grooves pitch and number of paths were considered and compared. The results shown that the decreasing of the pitch leads to an increase in both fluid velocity magnitude and vorticity magnitude, with an increasing of the mean values along the axial direction up to 21.4% for velocity and 37.2% for vorticity. Moreover, the number of grooves path along the die surface also affects the velocity field with an increasing of the mean values up to 14.5% for velocity.