Researchers from the Technological University of the Shannon in Ireland conducted a study in which they compared parts printed on 3D printers from pellets with parts printed from filaments. The tested material was PLA, and the tests concerned the strength and overall quality of the parts produced. The study results were published in the journal Additive Manufacturing and funded by the European Space Agency.
The main reason for the research was the desire to use used filament residues or waste generated during the 3D printing process (support structures, raft or failed 3D prints) in the form of granules. Previous studies in this area have produced mixed results – some have shown poorer mechanical performance of parts made from pellets, while others have reported comparable or slightly better performance. Regardless, these studies were limited to assessing tensile or flexural strength only and lacked a clear justification.
To address these uncertainties and research gaps, a comprehensive comparison and analysis of the mechanical performance of samples printed by these two types of plastic extrusion 3D printers was carried out. The tests carried out included tensile, impact, three-point bending and hardness tests. In addition, tests using an electron microscope (SEM), differential scanning calorimetry (DSC), thermal imaging, rheological tests and gel permeation chromatography (GPC) were performed.
PLA filament with a diameter of 1.75 mm, which was produced by Real Filament from the Netherlands, was used for the tests. Before entering the 3D printer, it was first dried at 40°C for 8 hours and stored in a vacuum package. The same filament cut into pieces 1-2.5 mm long was used for 3D printing from pellets. The parts used for the tests were printed at 200°C on 50°C heatbeds. The layer height is 0.1 mm and the filling was always 100%.
The results showed no significant differences (P > 0.05) in the mechanical properties of parts printed with filaments and granules in terms of tensile properties, flexural strength, modulus of elasticity and impact strength. However, there was a significant difference in Shore D hardness and bending stress at break between the two methods, and the composite viscosity of the printed pellet samples was greater than that of the filament counterparts.
Interestingly, the average molecular weights of the printed pellet samples were higher than those of the filament samples, which can be attributed to the former’s lower actual extrusion temperature due to its different location between the heater, thermistor and melting chamber compared to the traditional print head in FDM 3D printers. / FFF.
According to the researchers, thanks to the comparable mechanical properties of the printed samples, 3D printing from granules avoids the need to produce the filament and makes it possible to recycle thermoplastic waste. This results in cost savings, lower environmental impact and more efficient and streamlined 3D printing processes.
The full text of the study, along with a detailed analysis of the results obtained, can be read here.
Source: www.sciencedirect.com