Characterization of the effect of in-process annealing using a novel print head assembly on the ultimate tensile strength & toughness of Fused Filament Fabrication (FFF) parts

Improving the quality of parts printed using Fused Filament Fabrication (FFF) is of critical importance in a number of engineering applications. Providing additional thermal energy during printing by external means, or by an integrated heater has been investigated in the past to prolong the cooling curve, and therefore, ensure good adhesion with adjacent filaments. This work presents a modified heater block assembly to apply in-process thermal load during the upright printing of a Polylactic Acid (PLA) part. The design overcomes key shortcomings of past work and, in particular, addresses effective printing of thin, tall structures, where filament adhesion between layers is of particular importance. Cross-section imaging and tensile testing is combined with a comprehensive statistical design of experiments in order to fully understand the impact of process parameters on improved mechanical strength of printed parts. This work contributes towards improved properties and performance of realistic and practical FFF-printed parts.