Numerical Transient Thermal Development of Melting a Solid Filament in a Hot-end of a Material Extrusion System

Additive manufacturing of polymer feedstock in the form of solid filament is challenging due to heat transfer limitations. The ease of melting the filament in the liquefier influences the production rate and life cycle of the hot-end components. This study presents numerical transient thermal development during the melting of the solid filament in the liquefier. The sample filament material selected for the study is a tough polylactic acid (TPLA). The transient computation of thermal distribution and liquid fraction evolution was performed using computational fluid dynamics (CFD) commercial software. However, the numerical model formulations cannot be directly applied to the available CFD software. Therefore, a user-defined function (UDF) was written and interfaced with the CFD software for the properties field-dependent functions. Special care was taken to capture the motion of the solid filament by patching the velocity explicitly in the flow domain. One simulation was performed without accounting for the velocity of the translating solid filament and the result obtained revealed that the case that accounts for the velocity of the solid filament predicts the infrared thermographic measured nozzle exit temperature of the extrudate more accurately. Also, a steady thermal development was achieved in the hot end after 25 seconds. The transient thermal analysis can be useful for a better understanding of melting dynamics in the liquefier and assist in process control planning.