An investigation of the influence of 3d printing parameters on the tensile strength of PLA material

Fused Deposition Modelling (FDM), also known as 3d printing, is one of the most widespread Additive Manufacturing (AM) technologies based on the extrusion of a thermoplastic filament. This layerwise technology allows lightweight products to be built using different infill strategies and percentages. Furthermore, by varying other parameters, such as temperature, printing speed or layer thickness, it is possible to obtain components with different characteristics. Polylactic Acid (PLA) is one of the cheapest and most sustainable materials for 3d printing because it is a biobased and biodegradable plastic. Its use in 3D printing is widely spread among hobbyists and in the communities, such as the ones of Fablabs or the Makers movement.Nevertheless, to reduce the number of uncompliant parts that may fail into operation since they do not meet the expectations of the user, it is important to know in advance the mechanical performance that different 3d printing strategies can ensure for PLA parts.In this paper, Design of Experiment (DOE) is applied to investigate how main 3D printing parameters influence the tensile strength of PLA products. For this purpose, a 3x3 factorial plane with one replication was constructed and used for 3d printing tensile specimens of PLA Tough material using a Makerbot Replicator machine. The tensile test results show that the layer thickness is more significant than the infill percentage for the resistance of PLA products. A regression model is also proposed to allow the user to predict the ultimate tensile strength of PLA products depending on the values of those two parameters.Copyright (c) 2022 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the Third International Conference on Aspects of Materials Science and Engineering

Benchmarking analysis of digital light processing resins in terms of dimensional accuracy and geometric tolerances

Additive Manufacturing (AM) is a groundbreaking fabrication technology that is revolutionizing traditional manufacturing processes. Generally, following a layer-by-layer approach, in AM the final shape of the product is built through the progressive deposition of one or more materials. The most common extrusion-based AM technique for thermoplastic polymers is Fused Filament Fabrication (FFF), whilst for photopolymer resins, Digital Light Processing (DLP) and Stereolithography (SLA) are widely used. In the last years, DLP has spread rapidly, due to its low average cost and simple use. Moreover, a lower layer thickness can be used in DLP if compared to the FFF process. Therefore, hobbyists or amateur end users and many companies use DLP to achieve high dimensional accuracy and smooth surfaces for small products. This work aims to evaluate the performance of three different DLP resins in terms of dimensional and geometrical accuracy. A benchmarking activity is carried out using a Rover printer by Sharebot to produce replicas of a reference part using Sharebot resins. After production, the replicas were inspected using a Coordinate Measuring Machine (CMM) for comparing the dimensional accuracy of the geometric features according to ISO IT grades and tolerances of the GD&T system. The results of this study are also compared with previous works from the literature in the conclusions

Experimental validation of laser powder bed fusion simulation

In many industrial sectors, laser powder bed fusion (L-PBF) is the main additive manufacturing technology for producing end-usable metal parts. Although L-PBF technique has been developed in the last twenty years, ensuring process feasibility and achieving maximum product quality at the first building session is still a difficult goal to pursue. Simulation software packages are available in the market for the prediction of induced stresses and deformation in LPBF products to help the user getting the part right at the first time. In this paper, Amphyon software by Additive Works is tested and experimentally validated for the production of Ti6Al4V parts in an EOSINT M270 Dual Mode machine. First, the sensitivity of the software is evaluated by changing the main process parameters by +/- 20% with respect to Ti64 reference values. After calibration, the software is validated by comparison of the predicted deformed shape of a reference part with the real geometry using 3D scanning. Experimental results show that Amphyon software is able to predict the deformed shape for L-PBF parts correctly. The deviations from the real geometry depend on a simplified simulation model that considers a limited set of parameters for the L-PBF process

An investigation of the influence of 3d printing defects on the tensile performance of ABS material

Recently, the popularity of 3d printing for industrial and consumer use has spread across many different sectors. For this reason, quality assurance of 3d printed parts is becoming increasingly important. The extrusion and layer-by-layer deposition of a polymer filament on the print bed can introduce defects such as pores and voids into the internal structure of 3d printed parts. The relation between 3d printing defects and tensile performance of 3d printed samples is studied in this paper. The study considers tensile specimens of acrylonitrile butadiene styrene (ABS) that were 3d printed by varying the infill strategy and percentage to simulate different levels of strength for the part. Before the tensile tests, the ABS samples were inspected by X-ray tomography to identify the presence of internal voids generated by the 3d printing process. For each sample, data and statistics about the internal defects were used for determining a relation with the tensile test results. The local deformation of the sample and the position of the final fracture were observed using a digital camera and digital image correlation (DIC). In most cases, the experimental results confirmed the matching between the presence of internal voids and the areas of high deformation. However, the position of the specimen fracture did not always coincide with the largest defects. Nevertheless, this study highlights the importance of non-destructive inspection in quality assurance of 3d printed parts when in-situ monitoring of the 3d printing process is not applied. Copyright (C) 2022 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the Third International Conference on Aspects of Materials Science and Engineering

Experimental testing of 3D printed polymeric heat exchangers

Unlike conventional manufacturing technologies, additive manufacturing and 3D printing empower engineers with much more design freedom. Heat exchangers with complex internal channels or lattice structures can be designed for layerwise manufacturing by maximizing the surface to volume ratio. Low-weight polymeric heat exchangers are employed in aviation and aerospace applications. For increasing the thermal performance of polymers, additives can be used such as graphene. In this study, a Grafylon filament is used for the production of a simple heat exchanger by 3D printing. The heat exchanger is composed of two external shells and an interior duct with a two-stage 45-degree bend. For watertight purposes, the duct is manufactured by selective laser sintering of polyamide powder. Two replicas of the shells are fabricated by 3D printing of Grafylon and acrylonitrile butadiene styrene (ABS) respectively. The thermal performance of the two materials is experimentally tested and compared also to numerical simulations. The results of the study show that the Grafylon filament provides enhanced thermal performance to 3D printed heat exchangers of polymeric material

Experimental assessment of compensated distortion in selective laser melting of Ti6Al4V parts

Selective laser melting (SLM) is a well-established Additive Manufacturing technique for the fabrication of end-use metal components. Process reliability and maximum product quality are ensured by 20 years of technology development. Nevertheless, depending on the complexity of the part geometry and on the operator experience, different trials are often needed before getting a part first time right. To reduce the number of failed jobs, simulation software packages predict residual stresses and related distortions in SLM parts and propose a compensated geometry for the “right first time” production of the product. In this works, the simulation routines of Amphyon software by Additive Works are experimentally calibrated and validated for the fabrication of a reference geometry by means of an EOSINT M270 machine and Ti6Al4V powder. The calibration of Amphyon is performed using three cantilever specimens and the calibrated SLM simulation is then used to compute the compensated shape of the reference part. The validation of the compensated shape by comparison to the real part geometry shows that Amphyon routines have good prediction capability and dimensional accuracy

Development of a low-cost monitoring system for open 3d printing

3D printers for Rapid Prototyping and Additive Manufacturing have been widely accepted by large and small-scale industries or by many hobbyists. Due to its nature of layer by layer addition of material, identifying defects between the layers can be a crucial strategy to determine the quality of a 3D printed product by carefully monitoring the layerwise process during part building. This kind of approach gives an advantage in the applications where 3D printing of products requires high customization without compromise on part quality. In this work, a low-cost camera is installed in an open 3D printer, and computer vision algorithms are used to implement an in-situ monitoring system. The defects can be evaluated by comparing the printed layer to the deposition path of the open ISO G-code. The G-code printing file is modified to introduce the image capture step after each layer. The value of the area of missing or exceeding material is returned to the user with the corresponding images. A decision can be made to abort the job in case of important defects to avoid unnecessary waste in material, time, and costs

Abundance of intrinsic disorder in SV-IV, a multifunctional androgen-dependent protein secreted from rat seminal vesicle

The potent immunomodulatory, anti-inflammatory and procoagulant properties of the
protein no. 4 secreted from the rat seminal vesicle epithelium (SV-IV) have been
previously found to be modulated by a supramolecular monomer-trimer equilibrium.
More structural details that integrate experimental data into a predictive framework
have recently been reported. Unfortunately, homology modelling and fold-recognition
strategies were not successful in creating a theoretical model of the structural
organization of SV-IV. It was inferred that the global structure of SV-IV is not similar
to any protein of known three-dimensional structure. Reversing the classical approach
to the sequence-structure-function paradigm, in this paper we report on novel
information obtained by comparing physicochemical parameters of SV-IV with two
datasets made of intrinsically unfolded and ideally globular proteins. In addition, we
have analysed the SV-IV sequence by several publicly available disorder-oriented
predictors. Overall, disorder predictions and a re-examination of existing experimental
data strongly suggest that SV-IV needs large plasticity to efficiently interact with the
different targets that characterize its multifaceted biological function and should be
therefore better classified as an intrinsically disordered protein

Quantitative and qualitative effect of gH625 on the nanoliposome-mediated delivery of mitoxantrone anticancer drug to HeLa cells

The present work investigates in vitro the delivery of the anticancer drug mitoxantrone (MTX) to HeLa cancer cells by means of liposomes functionalized with the novel cell penetrating peptide gH625. This hydrophobic peptide enhances the delivery of doxorubicin to the cytoplasm of cancer cells, while the mechanism of this enhancement has not yet been understood. Here, in order to get a better insight into the role of gH625 on the mechanism of liposome-mediated drug delivery, we treated HeLa cells with liposomes functionalized with gH625 and loaded with MTX; liposome were characterized in terms of their physico-chemical properties and drug release kinetics. To quantify the MTX uptake and to study the subcellular drug distribution and interaction, we took advantage of the intrinsic fluorescence of MTX and of the fluorescence-based techniques like fluorescence-activated cell sorting (FACS) and confocal spectral imaging (CSI). gH625 liposomes showed an enhanced staining of the internalized drug is observed mainly in hydrophobic regions of the cytoplasm, where the increased presence of an oxidative metabolite of the drug is observed. MTX delivery with gH625-decorated nanoliposomes enhances the quantity of both the intracellular drug and of its oxidative metabolite and contributes to higher anticancer efficacy of the drug