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ORIGINAL RESEARCH

Thermal analysis of the fused filament fabrication printing process: Experimental and numerical investigations David Xu1 · Yancheng Zhang1 · Franck Pigeonneau1 Received: 1 August 2020 / Accepted: 15 September 2020 © Springer-Verlag France SAS, part of Springer Nature 2020

Abstract A 3d printing of a thin wall is achieved by a fused filament fabrication process. The influence of the printing velocities on the filament morphology is studied using optical microscopy. The strand morphology is approximated to different geometries and compared to experimental data. The oblong cross-section is a good approximation to estimate the strand’s height and width. A local temperature is recorded by introducing a thermocouple during the printing of a thin wall. The polymer undergoes successive heating and cooling. Their magnitudes decrease with time while the filament deposition occurs farther from the thermocouple location. A steady-state cooling is observed after an extended period of time due to the surrounding air cooling. The influence of the strand’s cross-section area on its cooling kinetics is investigated experimentally. The printing of a thin wall with the same geometry is also numerically computed by solving the heat transfer equation with a finite element method. The thermal conductivity takes into account the porosity of the printed wall. An estimation of the heat transfer coefficients between the wall and the surrounding air is done by comparison with a particular experiment. The numerical computation reproduces very well the amplitudes and the periods of heating and cooling observed experimentally. Moreover, the changes in the morphology of the melted filament show the reliability of the numerical tool to obtain a thermal history in agreement with experimental data. Keywords 3d printing · Material extrusion · Amorphous polymer · Heat transfer · Strand morphology · Finite element analysis

Introduction Additive manufacturing (AM) is a widely growing technology due to its ability to build objects with complex shapes. Moreover, this process minimises post-processing and reduces material wastes. Different materials can be printed such as metals, ceramics and polymers [4]. Techniques such as laser-based processes, extrusion processes,

 Franck Pigeonneau

[email protected] David Xu [email protected] Yancheng Zhang [email protected] 1

MINES ParisTech, PSL Research University, CEMEF – Centre for material forming, CNRS UMR 7635, CS 10207, rue Claude Daunesse 06904 Sophia Antipolis Cedex, France

material jetting, adhesive or electron beams are being developed. The Fused Filament Fabrication (FFF) process is based on the deposition of melted polymer filaments to create an object from a 3d CAD model [8]. This process is widely used since it is easy to operate, reproducible, low cost and can accept sustainable materials [7]. According to Goh et al. [8], the melting and solidification of thermoplastics is an open problem due to fast heating and cooling during the