Processing and Quality Evaluation of Additive Manufacturing Monolayer Specimens

Abstract

Although its importance has increased significantly, Additive Manufacturing is not yet a fully accepted industrial manufacturing process for load-carrying parts. The future success of the process group depends on its standardization. This work proposes a methodology for the design, manufacturing, and quality evaluation of specimens manufactured by Fused Layer Modeling that are composed of only one layer (so-called monolayers). The processing methodology and properties of monolayers have not been studied systematically yet. A first systematic design of monolayers for mechanical testing is presented. Rectangular and circular monolayers adapted to the loads of tensile and compression testing are manufactured using different trajectory strategies. Frequently occurring macro- and microgeometrical defects are evaluated and categorized in order to optimize the part quality. This work also studies the effect of some manufacturing parameters such as the gap between print head and machine bed, trajectory strategy, bed leveling, and temperatures on part quality. The most suitable specimens are tested mechanically in tensile or compression tests. In the case of study, tensile strength values are only 8.6% lower than the values for reference tests on the unextruded filament. However, the properties deviate more strongly for compression tests which may be due to the selected specimen geometry.

Influence of PLA Filament Conditions on Characteristics of FDM Parts

“…The manifestation of this defect, which at lower temperatures is almost non-existent, is due to the fact that at high temperatures the material reaches the extruder nozzle practically liquid. According to other authors, this is due to the fact that at higher temperatures the viscosity decreases [6,7,16]. The PLA, by the time it slides through the nozzle, produces friction with the walls which in turn generates turbulence contributing to the air intake.…”

“…Other more recent authors as C. Wendt et al [6] determined a specific geometry for monolayer samples’ dimensions and trajectories suitable for conducting studies with tensile tests. These dimensions and trajectories are reflected in Figure 2.…”

“…On the other hand, S-H. Anh et al [ 17 ] have analyzed different possible trajectories for the manufacture of monolayer specimens. Other more recent authors as C. Wendt et al [ 6 ] determined a specific geometry for monolayer samples’ dimensions and trajectories suitable for conducting studies with tensile tests. These dimensions and trajectories are reflected in Figure 2 .…”

“…This causes improbable geometric deviations, as well as a characteristic roughness associated with layer stacking. Additionally, there is still a lack of information, communication, standardization, and consequent development of these processes [4,5,6]. …”

Analytical Modelling and Optimization of the Temperature-Dependent Dynamic Mechanical Properties of Fused Deposition Fabricated Parts Made of PC-ABS

“…Biranchi et al [ 12 ] demonstrated that the slice height and extrusion velocity have great effect on the deformation, while filling velocity and line width compensation have strong effect on the dimensional accuracy of FDM built part. Wendt et al [ 13 ] studied the impact of manufacturing conditions on the tensile and compression strength of FDM processed prototypes. Lanzotti et al [ 14 ] carried out an experimental study on the effect of process parameters on tensile strength of FDM fabricated part by PLA.…”