An Investigation of in Fill Process Variables to Reduce Warpage in Fused Filament Fabrication

Currently, three-dimensional (3D) printing is being widely used for rapid pro-totyping and Just in Time manufacturing. Many commercial 3D printers use fused filament fabrication (FFF), a printing technique where a solid thermo-plastic filament is melted and extruded onto sequential two-dimensional layers to produce a 3D object. In FFF printing, thermal stresses between layers due to inhomogeneous thermal conduction during cycles of heating and cooling create distortions, known as warpage. Process variables, especially infill density and infill pattern, cause thermal properties to become anisotropic because of thermal conduction through plastic and natural convection in air gaps. In order to identify the effect of these process variables on thermal warpage, Polylactic Acid (PLA) discs with varying infill densities and patterns were printed and the spatiotemporal temperature distribution was modeled. Trajectory similarity analysis using the Dynamic Time Warping algorithm as well as a temperature gradient analysis with statistical tests were conducted. Based on the analysis of the data, this study recommends that 30% infill density and trihexagonal infill pattern be used in FFF printing with PLA to mitigate the warpage. Keywords—Warpage; fused filament fabrication; infill; temperature distribution; thermal stress; dynamic time warping