Investigating the effects of extrusion temperatures and material extrusion rates on FFF-printed thermoplastics

Fused filament fabrication (FFF) is one of the most widely used additive manufacturing processes in the market. It is based on material extrusion and utilises thermoplastic materials to manufacture bespoke products. The process is extremely popular due to its ease of operation and variety of available materials. To enhance the mechanical performance of parts made by FFF, reinforcements including nanoparticles, short or continuous fibres, and other additives have been added to commonly used thermoplastics such as acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA). Such new materials require optimisation of process parameters to achieve the desired results. One such parameter is the material extrusion rate that can result in under- or over-extrusion leading to a variety of applications. In this study, PLA and HDPlas® PLA-GNP-A (PLA reinforced with functionalised graphene nanoplatelets) have been used to investigate the effects of material extrusion rate. An extensive comparative analysis has been provided where parts have been manufactured using a desktop 3D printer with the two materials at four extrusion temperatures (180 °C, 190 °C, 200 °C, and 210 °C) and ten different extrusion rates (ranging from 70 to 160%). The study aims to evaluate the effects of extrusion temperatures and material extrusion rates on mass, dimensional accuracy, surface texture, and mechanical properties of the two materials. Microstructural analysis has also been carried out to evaluate the surfaces of parts after manufacture as well as their fractured surfaces after mechanical testing to determine the impact of extrusion rate on failure modes. The results have shown that the graphene reinforced PLA material is affected more adversely by changes in material extrusion rate compared to PLA. This work provides a good comparison between two materials manufactured at four different extrusion temperatures and how the material extrusion rate can be leveraged to achieve optimal surface finish and mechanical strength.