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THIN films, RAPID prototyping, SURFACE roughness, SURFACES (Technology), and MECHANICAL models

Surface quality is a very important factor to be considered in determining part build orientation in rapid prototyping (RP) processes. Previous research has shown that parts built with inclined planes or curved surfaces along the build orientation have large staircase effect, thus have higher surface roughness compared to parts built with only vertical surfaces. However, as layers are getting thinner in rapid prototyping processes, the opposite might be true. In this study, a number of experiments and measurements are conducted first. In a single machine setup, two cylinders are built, one along axial direction and the other along transverse direction using an Objet® machine. Measurements have shown that surface roughness of RP parts built along the transverse direction is better than those from the axial direction. Through analysis and observation, the authors can conclude that when layers are small enough, surface curvature or slope along the build orientation may no longer be a major concern for RP part surface quality. Instead, the authors have observed that on-the-layer contour layout may cause even more serious surface quality problem. In other words, surface quality is not only dependent on build orientation, but more on scanning orientation on layers. [ABSTRACT FROM AUTHOR]

ARTIFICIAL saliva, GEOMETRY, RAPID prototyping, DETERIORATION of materials, TRANSVERSAL lines, and SHAPE memory polymers

Additive manufacturing of polymers has evolved from rapid prototyping to the production of functional components/parts with applications in distinct areas, ranging from health to aeronautics. The possibility of producing complex customized geometries with less environmental impact is one of the critical factors that leveraged the exponential growth of this processing technology. Among the several processing parameters that influence the properties of the parts, the geometry (shape factor) is amid less reported. Considering the geometric complexity of the mouth, including the uniqueness of each teething, this study can contribute to a better understanding of the performance of polymeric devices used in the oral environment for preventive, restorative, and regenerative therapies. Thus, this work aims to evaluate 3D printed poly(ε-caprolactone) mechanical properties with different build orientations and geometries. Longitudinal and transversal toolpaths produced specimens with parallelepiped and tubular geometry. Moreover, as it is intended to develop devices for dentistry, the influence of artificial saliva on mechanical properties was determined. The research concluded that the best mechanical properties are obtained for parallelepiped geometry with a longitudinal impression and that aging in artificial saliva negatively influences all the mechanical properties evaluated in this study. [ABSTRACT FROM AUTHOR]

RESPONSE surfaces (Statistics), SURFACE finishing, and SURFACE roughness

Purpose: The advancement of additive manufacturing technologies has resulted in producing parts of high quality and reduced manufacturing time. This paper aims to achieve a simultaneous optimal solution for build time and surface roughness as the output data and also to find the best values for the input data consisting of build orientation, extrusion width, layer thickness, infill percentage and raster angle. Design/methodology/approach: For this purpose, the effects of process parameters on the response variables were investigated by the design of experiments approach to develop empirical models using response surface methodology. The experimental parts of this research were conducted using an inexpensive and locally assembled fused filament fabrication (FFF) machine. A total of 50 runs for 4 different geometries, namely, cylinder, prism, 3DBenchy and twist gear vase, were performed using the rotatable central composite design, and each process parameters were investigated in two levels to develop empirical models. Also, a novel optimization method, namely, the posterior-based method, was accomplished to find the best values for the response variables. Findings: The results demonstrated that not only the build orientation and layer thickness have notable effects on both response variables but also build time is dependent on extrusion width and infill percentage. Low infill percentage and high extrusion width resulted in increasing build time. By reducing layer thickness and infill percentage while increasing extrusion width, parts of high-quality surface finish and reduced built time were produced. Optimum process parameters were found to be of build direction of 0°, extrusion width of 0.61 mm, layer thickness of 0.22 mm, infill percentage of 20% and raster angle of 0°. Originality/value: Through the developed empirical models and by minimizing build orientation and layer thickness, and also considerations for process parameters, parts of high-quality surface finish and reduced built time could be produced on FFF machines. To compensate for increased build time because of reduction in layer thickness, extrusion width and infill percentage must have their maximum and minimum value, respectively. [ABSTRACT FROM AUTHOR]

FRACTURE toughness, MELTING, BULK solids, LASERS, FRACTOGRAPHY, and METALLOGRAPHY

Purpose: A key challenge found in additive manufacturing is the difficulty to produce components with replicable microstructure and mechanical performance in distinct orientations. This study aims to investigate the influence of build orientation on the fracture toughness of additively manufactured AlSi10Mg specimens. Design/methodology/approach: The AlSi10Mg specimens were manufactured using the selective laser melting (SLM) technology. The fracture toughness was experimentally determined (under ASTM E399-09) using C(T) specimens manufactured in different orientations. The microstructure of the specimens was examined using metallography to determine the effects of grain orientation on fracture toughness. Findings: The fracture toughness magnitude of manufactured specimens ranged between 36 and 50 MPam, which closely matched conventional bulk material and literature values regarding AlSi10Mg components. The C(T) specimens printed in the T-L orientation yielded the highest fracture toughness. The grain orientation and fracture toughness values confirm the anisotropic nature of SLM parts where the T-L-oriented specimen obtained the highest KIC value. A clear interaction between the melt pool boundaries and micro-slipping during the loading application was observed. Originality/value: The novelty of this paper consists in elucidating the relationship between grain orientation and fracture toughness of additively manufactured AlSi10Mg specimens because of the anisotropy generated by the different melting pool boundaries and orientations in SLM. The findings show that melt pool boundaries can behave as easier pathways for cracks to propagate and subsequently reduce the fracture toughness of specimens with cracks perpendicular to the build direction. [ABSTRACT FROM AUTHOR]

FUSED deposition modeling, POLYLACTIC acid, TENSILE tests, NUMERICAL analysis, and BEHAVIOR

Purpose: This paper aims to investigate the structural behaviour of polylactic acid (PLA) parts fabricated by fused deposition modelling (FDM) to support the development of analytical and numerical models to predict the structural performance of FDM components and categories of similar additive manufactured parts. Design/methodology/approach: A new methodology based on uniaxial tensile tests of filaments and FDM specimens, infill measurement and normalization of the results is proposed and implemented. A total of 396 specimens made of PLA were evaluated by using variable process parameters. Findings: The infill and the build orientation have a large influence on the elastic modulus and ultimate tensile stress, whereas the layer thickness and the infill pattern have a low influence on these properties. The elongation at break is not influenced by the process parameters except by the build orientation. Furthermore, the infill values measured on the test specimens differ from the nominal values provided by the system. Research limitations/implications: The analysis of the structural properties of FDM samples is limited to uniaxial loading conditions. Practical implications: The obtained results are valuable for the structural analysis and numerical simulation of FDM components and for potential studies using machine learning techniques to predict the structural response of FDM parts. Originality/value: A new experimental methodology that considers the measurement of the real infill percentage and the normalization of the results for inter-comparison with other studies is proposed. Moreover, a new set of experimental results of FDM-PLA parts is presented and extends the existing results in the literature. [ABSTRACT FROM AUTHOR]

SELECTIVE laser sintering, TENSILE strength, POLYAMIDES, FIBER orientation, FLEXURAL modulus, FLEXURAL strength, and CONCRETE-filled tubes

Purpose: The cement-filled PA12 manufactured by selective laser sintering (SLS) offers desirable mechanical properties; however, these properties are dependent on several fabrication parameters. As a result, SLS prototypes may exhibit orthotropic mechanical properties unless properly oriented in build chamber. This paper aims to evaluate the effects of part build orientation, laser energy and cement content on mechanical properties of cement-filled PA12. Design/methodology/approach: The test specimens were fabricated by SLS using the "DTM Sinterstation 2000" system at which the specimens were aligned along six different orientations. The scanning speed was 914mm/s, scan spacing was 0.15mm, layer thickness was 0.1mm and laser power was 4.5–8Watt. A total of 270 tensile specimens, 270 flexural specimens and 135 compression specimens were manufactured and the tensile, compression and flexural properties of fabricated specimens were evaluated. Findings: The experiments revealed orientation-dependent (orthotropic) mechanical properties of SLS cement-filled PA12 and confirmed that the parts with shorter scan vectors have enhanced flexural strength as compared with longer scan vectors. The maximum deviations of ultimate tensile strength, compressive strength and flexural modulus along the six orientations were 32%, 26% and 36%, respectively. Originality/value: Although part build orientation is a key fabrication parameter, very little was found in open literature with contradictory findings about its effect on mechanical properties of fabricated parts. In this work, the effects of build orientation when combined with other fabrication parameters on the properties of SLS parts were evaluated along six different orientations. [ABSTRACT FROM AUTHOR]

THREE-dimensional printing, TENSILE strength, 3-D printers, SCANNING electron microscopes, and FRACTURE mechanics

Purpose The main purpose of this paper is to investigate the influence of build orientation on the tensile properties of PolyJet 3D printed parts. Effects on manufacturing time and total cost per part are the secondary objectives.Design/methodology/approach Solid tensile specimens were prepared as per the American Society for Testing and Materials D638 standards and were manufactured in six different orientations by using the Objet260 Connex 3D printer. VeroWhitePlus RGD835 was used as the build material, with FullCure 705 as the support material. The specimens were tested for their tensile strength and elongation. The side surface and the fracture surface were analyzed using the Field Emission Scanning Electron Microscope-SIGMA HV-Carl Zeiss with Bruker Quantax 200-Z10 EDS detector. Scanning electron microscope images of each surface were obtained at various magnifications.Findings From the study, it can be concluded that build orientation has an influence on the tensile strength and the manufacturing cost of the parts. The microstructural analysis revealed that the orientation of surface cracks/voids may be the reason for the strength.Originality/value From literature survey, it is inferred that this study is sure to be among the first few under this topic. These results will help engineers to decide upon the right build orientations with respect to print head so that parts with better mechanical properties can be manufactured. [ABSTRACT FROM AUTHOR]