Articles de revues : « 3D extruded geometries »

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Teixeira, João, Cecília Ogliari Schaefer, Lino Maia, Bárbara Rangel, Rui Neto et Jorge Lino Alves. « Influence of Supplementary Cementitious Materials on Fresh Properties of 3D Printable Materials ». Sustainability 14, n^o 7 (28 mars 2022) : 3970. http://dx.doi.org/10.3390/su14073970.

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The development of printers and materials for 3D Printing Construction during the last two decades has allowed the construction of increasingly complex projects. Some of them have broken construction speed records due to the simplification of the construction process, particularly in non-standard geometries. However, for performance and security reasons the materials used had considerable amounts of Portland cement (PC), a constituent that increases the cost and environmental impact of 3D Printable Materials (3DPM). Supplementary Cement Materials (SCM), such as fly ash, silica fume and metakaolin, have been considered a good solution to partially replace PC. This work aims to study the inclusion of limestone filler, fly ash and metakaolin as SCM in 3DPM. Firstly, a brief literature review was made to understand how these SCM can improve the materials’ 3DP capacity, and which methods are used to evaluate them. Based on the literature review, a laboratory methodology is proposed to assess 3DP properties, where tests such as slump and flow table are suggested. The influence of each SCM is evaluated by performing all tests on mortars with different dosages of each SCM. Finally, a mechanical extruder is used to extrude the developed mortars, which allowed us to compare the results of slump and flow table tests with the quality of extruded samples.

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Sciannandrone, Daniele, Simone Santandrea et Richard Sanchez. « Optimized tracking strategies for step MOC calculations in extruded 3D axial geometries ». Annals of Nuclear Energy 87 (janvier 2016) : 49–60. http://dx.doi.org/10.1016/j.anucene.2015.05.014.

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Buj-Corral, Irene, José Antonio Padilla, Joaquim Minguella-Canela, Lourdes Rodero, Lluís Marco et Elena Xuriguera. « Design of Pastes for Direct Ink Writing of Zirconia Parts with Medical Applications ». Key Engineering Materials 958 (5 octobre 2023) : 157–63. http://dx.doi.org/10.4028/p-izk9dd.

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Direct ink writing (DIW) is an extrusion additive manufacturing (AM) technique in which inks are extruded through a nozzle and then deposited layer-by-layer. This technology allows 3D printing many different materials such as ceramics, metals, food, etc. In this work, the performance of zirconia pastes is addressed. The pastes are composed of yttria stabilized zirconia (YSZ) powder and a polymeric binder. Ceramic content is a mix of two components: A and B. Both the total content of ceramic and the content of component A in the paste are varied, according to a 32 design of experiments. The paste was characterized regarding Densification (%) and Elastic modulus G’ (Pa). A new parameter w3/G’ is defined to evaluate the viscosity of the inks. In the tests, the ceramic percentage is limited by the pressing force of the plunger that will be used to extrude the pastes. On the other hand, the binder concentration is also limited, because it requires to be in a gel form in order to be properly extruded. The results showed that Densification depends mainly on ceramic content, while the w3/G’ parameter is related to percentage of component A. In this work, the properties of the pastes prior to 3D printing are assessed. However, in the future, the pastes will be used to extrude complex parts with medical applications. AM extrusion processes constitute a possible way to overcome the difficulties to obtain complex geometries with conventional methods such as machining, in which zirconia parts can break due to their brittleness. Thus, the results of this work will help to manufacture complex shapes with porous areas in zirconia, when the DIW technology is employed.

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Rufo-Martín, Celia, José Díaz-Álvarez et Diego Infante-García. « Influence of PMMA 3D Printing Geometries on the Mechanical Response ». Key Engineering Materials 958 (5 octobre 2023) : 31–39. http://dx.doi.org/10.4028/p-9tor3c.

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This work presents a study regarding the mechanical characterization of polymethyl methacrylate (PMMA) patterned samples manufactured via material-extruded additive manufacturing. In recent years, literature about mechanical analysis in additive manufacturing has been growing increasingly, especially for material extrusion-based techniques. However, this trend surpasses the speed of information released by standard councils, existing no clear specifications for polymer characterization apart from conventional techniques. This issue has led to premature breakage as well as fracture not located in the constant cross-section region of samples. The main purpose of this present research is focused on the analysis of diverse modifications of the standard injection geometries to tackle the mentioned problems. Several printing methodologies were compared, changing slicing and geometrical parameters such as number of walls, and fillet radius. Then, the manufacturing of PMMA samples with a material extrusion printer took place to characterize both the material and the effective properties of the structures. With the information post-processed from tensile and compression tests, disparities were found between different geometrical designs for both elastic modulus and ultimate stress. Moreover, diverse location of fractures were observed for the studied geometries. The data obtained from the analysis was valuable to establish a proper protocol for further studies. The experiments suggest that for tensile tests the golden standard is selecting rectangular specimens since they do not induce premature breakage nor fracture outside of gauge length.

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Graziano, Laurent, Simone Santandrea et Daniele Sciannandrone. « Polynomial axial expansion in the Method of Characteristics for neutron transport in 3D extruded geometries ». EPJ Web of Conferences 153 (2017) : 06027. http://dx.doi.org/10.1051/epjconf/201715306027.

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Mitchell, Kellen, Lily Raymond et Yifei Jin. « Material Extrusion Advanced Manufacturing of Helical Artificial Muscles from Shape Memory Polymer ». Machines 10, n^o 7 (22 juin 2022) : 497. http://dx.doi.org/10.3390/machines10070497.

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Rehabilitation and mobility assistance using robotic orthosis or exoskeletons have shown potential in aiding those with musculoskeletal disorders. Artificial muscles are the main component used to drive robotics and bio-assistive devices. However, current fabrication methods to produce artificial muscles are technically challenging and laborious for medical staff at clinics and hospitals. This study aims to investigate a printhead system for material extrusion of helical polymer artificial muscles. In the proposed system, an internal fluted mandrel within the printhead and a temperature control module were used simultaneously to solidify and stereotype polymer filaments prior to extrusion from the printhead with a helical shape. Numerical simulation was applied to determine the optimal printhead design, as well as analyze the coupling effects and sensitivity of the printhead geometries on artificial muscle fabrication. Based on the simulation analysis, the printhead system was designed, fabricated, and operated to extrude helical filaments using polylactic acid. The diameter, thickness, and pitch of the extruded filaments were compared to the corresponding geometries of the mandrel to validate the fabrication accuracy. Finally, a printed filament was programmed and actuated to test its functionality as a helical artificial muscle. The proposed printhead system not only allows for the stationary extrusion of helical artificial muscles but is also compatible with commercial 3D printers to freeform print helical artificial muscle groups in the future.

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Kothavade, Premkumar, Abdullah Kafi, Chaitali Dekiwadia, Viksit Kumar, Santhosh Babu Sukumaran, Kadhiravan Shanmuganathan et Stuart Bateman. « Extrusion 3D Printing of Intrinsically Fluorescent Thermoplastic Polyimide : Revealing an Undisclosed Potential ». Polymers 16, n^o 19 (2 octobre 2024) : 2798. http://dx.doi.org/10.3390/polym16192798.

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Thermoplastic polyimides (TPIs) are promising lightweight materials for replacing metal components in aerospace, rocketry, and automotive industries. Key TPI attributes include low density, thermal stability, mechanical strength, inherent flame retardancy, and intrinsic fluorescence under UV light. The application of advanced manufacturing techniques, especially 3D printing, could significantly broaden the use of TPIs; however, challenges in melt-processing this class of polymer represent a barrier. This study explored the processability, 3D-printing and hence mechanical, and fluorescence properties of TPI coupons, demonstrating their suitability for advanced 3D-printing applications. Moreover, the study successfully 3D-printed a functional impeller for an overhead stirrer, effectively replacing its metallic counterpart. Defects were shown to be readily detectable under UV light. A thorough analysis of TPI processing examining its rheological, morphological, and thermal properties is presented. Extruded TPI filaments were 3D-printed into test coupons with different infill geometries to examine the effect of tool path on mechanical performance. The fluorescence properties of the 3D-printed TPI coupons were evaluated to highlight their potential to produce intricately shaped thermally stable, fluorescence-based sensors.

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Nikfarjam, F., Y. Cheny et O. Botella. « The LS-STAG immersed boundary/cut-cell method for non-Newtonian flows in 3D extruded geometries ». Computer Physics Communications 226 (mai 2018) : 67–80. http://dx.doi.org/10.1016/j.cpc.2018.01.006.

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Ferro, Paolo, Alberto Fabrizi, Hamada Elsayed et Gianpaolo Savio. « Multi-Material Additive Manufacturing : Creating IN718-AISI 316L Bimetallic Parts by 3D Printing, Debinding, and Sintering ». Sustainability 15, n^o 15 (2 août 2023) : 11911. http://dx.doi.org/10.3390/su151511911.

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Allowing for complex shape and low energy consumption, 3D printing, debinding, and sintering (PDS) is a promising and cost-effective additive manufacturing (AM) technology. Moreover, PDS is particularly suitable for producing bimetallic parts using two metal/polymer composite filaments in the same nozzle, known as co-extrusion, or in different nozzles, in a setup called bi-extrusion. The paper describes a first attempt to produce bimetallic parts using Inconel 718 and AISI 316L stainless steel via PDS. The primary goal is to assess the metallurgical characteristics, part shrinkage, relative density, and the interdiffusion phenomenon occurring at the interface of the two alloys. A first set of experiments was conducted to investigate the effect of deposition patterns on the above-mentioned features while keeping the same binding and sintering heat treatment. Different sintering temperatures (1260 °C, 1300 °C, and 1350 °C) and holding times (4 h and 8 h) were then investigated to improve the density of the printed parts. Co-extruded parts showed a better dimensional stability against the variations induced by the binding and sintering heat treatment, compared to bi-extruded samples. In co-extruded parts, shrinkage depends on scanning strategy; moreover, the higher the temperature and holding time of the sintering heat treatment, the higher the density reached. The work expands the knowledge of PDS for metallic multi-materials, opening new possibilities for designing and utilizing functionally graded materials in optimized components. With the ability to create intricate geometries and lightweight structures, PDS enables energy savings across industries, such as the aerospace and automotive industries, by reducing component weight and enhancing fuel efficiency. Furthermore, PDS offers substantial advantages in terms of resource efficiency, waste reduction, and energy consumption compared to other metal AM technologies, thereby reducing environmental impact.

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Cai, Yuanzhi, et Lei Fan. « An Efficient Approach to Automatic Construction of 3D Watertight Geometry of Buildings Using Point Clouds ». Remote Sensing 13, n^o 10 (17 mai 2021) : 1947. http://dx.doi.org/10.3390/rs13101947.

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Recent years have witnessed an increasing use of 3D models in general and 3D geometric models specifically of built environment for various applications, owing to the advancement of mapping techniques for accurate 3D information. Depending on the application scenarios, there exist various types of approaches to automate the construction of 3D building geometry. However, in those studies, less attention has been paid to watertight geometries derived from point cloud data, which are of use to the management and the simulations of building energy. To this end, an efficient reconstruction approach was introduced in this study and involves the following key steps. The point cloud data are first voxelised for the ray-casting analysis to obtain the 3D indoor space. By projecting it onto a horizontal plane, an image representing the indoor area is obtained and is used for the room segmentation. The 2D boundary of each room candidate is extracted using new grammar rules and is extruded using the room height to generate 3D models of individual room candidates. The room connection analyses are applied to the individual models obtained to determine the locations of doors and the topological relations between adjacent room candidates for forming an integrated and watertight geometric model. The approach proposed was tested using the point cloud data representing six building sites of distinct spatial confirmations of rooms, corridors and openings. The experimental results showed that accurate watertight building geometries were successfully created. The average differences between the point cloud data and the geometric models obtained were found to range from 12 to 21 mm. The maximum computation time taken was less than 5 min for the point cloud of approximately 469 million data points, more efficient than the typical reconstruction methods in the literature.

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Charbonneau, André M., Joseph M. Kinsella et Simon D. Tran. « 3D Cultures of Salivary Gland Cells in Native or Gelled Egg Yolk Plasma, Combined with Egg White and 3D-Printing of Gelled Egg Yolk Plasma ». Materials 12, n^o 21 (24 octobre 2019) : 3480. http://dx.doi.org/10.3390/ma12213480.

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For salivary gland (SG) tissue engineering, we cultured acinar NS-SV-AC cell line or primary SG fibroblasts for 14 days in avian egg yolk plasma (EYP). Media or egg white (EW) supplemented the cultures as they grew in 3D-Cryo histology well inserts. In the second half of this manuscript, we measured EYP’s freeze-thaw gelation and freeze-thaw induced gelled EYP (GEYP), and designed and tested further GEYP tissue engineering applications. With a 3D-Cryo well insert, we tested GEYP as a structural support for 3D cell culture or as a bio-ink for 3D-Bioprinting fluorescent cells. In non-printed EYP + EW or GEYP + EW cultures, sagittal sections of the cultures showed cells remaining above the well’s base. Ki-67 expression was lacking for fibroblasts, contrasting NS-SV-AC’s constant expression. Rheological viscoelastic measurements of GEYP at 37 °C on seven different freezing periods showed constant increase from 0 in mean storage and loss moduli, to 320 Pa and 120 Pa, respectively, after 30 days. We successfully 3D-printed GEYP with controlled geometries. We manually extruded GEYP bio-ink with fluorescence cells into a 3D-Cryo well insert and showed cell positioning. The 3D-Cryo well inserts reveal information on cells in EYP and we demonstrated GEYP cell culture and 3D-printing applications.

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Santandrea, S., D. Sciannandrone, R. Sanchez, L. Mao et L. Graziano. « A Neutron Transport Characteristics Method for 3D Axially Extruded Geometries Coupled with a Fine Group Self-Shielding Environment ». Nuclear Science and Engineering 186, n^o 3 (10 mai 2017) : 239–76. http://dx.doi.org/10.1080/00295639.2016.1273634.

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Son, Kyu-Hyon, Jung-Hun Kim, Dong-Eun Kim, Min-Sik Kang, Joo-Heon Song, Moon-Soo Choi, Sang-Mok Chang, Hoon-Kyu Shin et Sung-Woong Han. « Analysis of Correlation Between Contrast and Component of Polylatic Acid Composite for Fused Deposition Modeling 3D Printing ». Journal of Nanoscience and Nanotechnology 20, n^o 8 (1 août 2020) : 5107–11. http://dx.doi.org/10.1166/jnn.2020.17835.

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Additive manufacturing or three-dimensional (3D) printing is considered a disruptive technology for producing components with topologically optimized complex geometries as well as functionalities that are not achievable by traditional methods. 3D printing is expected to revolutionize the manufacturing of components. While several 3D printing systems are available, printing based on fused-deposition modeling (FDM) using thermoplastics is particularly widespread because of the simplicity and potential applicability of the method. In this study, we report the analysis of correlation between contrast and component of polylactic acid (PLA) based composite for FDM 3D printing. The pre-fabricated white composite and black composite were mixed in the fraction of 100:0, 90:10, 75:25, 50:50, 25:75, and 0:100% (v/v) and the obtained mixture was extruded using HX-35 3D filament extrusion line. The samples in different contrast were printed in disk like shape, and the gray scale filaments and 3D printed samples were measured the morphology and components using a field emission scanning electron microscope and energy dispersive X-ray spectroscopy. The CIE-lab values of the samples were measured using a colorimeter and the correlation between CIE-lab values and the components were analyzed. Although the component of Ti was linearly increased, the CIE-lab values show a clear exponential increase by increasing the white composite.

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Mendibil, Xabier, Gaizka Tena, Alaine Duque, Nerea Uranga, Miguel Ángel Campanero et Jesús Alonso. « Direct Powder Extrusion of Paracetamol Loaded Mixtures for 3D Printed Pharmaceutics for Personalized Medicine via Low Temperature Thermal Processing ». Pharmaceutics 13, n^o 6 (19 juin 2021) : 907. http://dx.doi.org/10.3390/pharmaceutics13060907.

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Three-dimensional printed drug development is nowadays an active area in the pharmaceutical industry, where the search for an appropriate edible carrier that permits the thermal processing of the mixture at temperature levels that are safe for the drug is an important field of study. Here, potato starch and hydroxypropyl cellulose based mixtures loaded with paracetamol up to 50% in weight were processed by hot melt extrusion at 85 °C to test their suitability to be thermally processed. The extruded mixtures were tested by liquid chromatography to analyze their release curves and were thermally characterized. The drug recovery was observed to be highly dependent on the initial moisture level of the mixture, the samples being prepared with an addition of water at a ratio of 3% in weight proportional to the starch amount, highly soluble and easy to extrude. The release curves showed a slow and steady drug liberation compared to a commercially available paracetamol tablet, reaching the 100% of recovery at 60 min. The samples aged for 6 weeks showed slower drug release curves compared to fresh samples, this effect being attributable to the loss of moisture. The paracetamol loaded mixture in powder form was used to print pills with different sizes and geometries in a fused deposition modelling three-dimensional printer modified with a commercially available powder extrusion head, showing the potential of this formulation for use in personalized medicine.

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Pariona, Moises Meza. « Simulation by coupling of the level set and thermal methods to extruded material flow in 3D printed polymers ». CONTRIBUCIONES A LAS CIENCIAS SOCIALES 16, n^o 12 (20 décembre 2023) : 32219–35. http://dx.doi.org/10.55905/revconv.16n.12-188.

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Fused deposition modelling (FDM) in polymers provides new opportunities for the manufacturing of components with customizable geometries and mechanical properties, with high speed and low cost. To this end, we propose a computational framework for the simulation of the printing process of the flow during low density polyethylene (LDPE) material extrusion, coupled to thermal, level set method and CFD phenomena. This work presents an FEM (finite element method) mathematical model that describes as result of the melt parameters of the polymer flow, such as, the volume fraction, temperature field, the pressure distribution of the mixed phase, velocity distribution, temperature gradient field and viscosity dynamic in different times, in different parts of the extruder geometry of a 3D printer, based on FDM technique. The result of the melt parameters in the process are not uniform; they vary across in the cross-section area of the nozzle and in the form area for depositing the material. The result was coherent with the literature.

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Li, Mingyang, Zhixin Liu, Jin Yao Ho et Teck Neng Wong. « Improving Homogeneity of 3D-Printed Cementitious Material Distribution for Radial Toolpath ». Fluids 8, n^o 3 (1 mars 2023) : 87. http://dx.doi.org/10.3390/fluids8030087.

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The 3D cementitious material printing method is an extrusion-based additive manufacturing strategy in which cementitious materials are extruded through a dynamic nozzle system to form filaments. Despite its ability to fabricate structures with high complexity and efficiency, the uneven material distribution during the extrusion and deposition process is often encountered when a radial toolpath is introduced. This limits the design freedom and printing parameters that can be utilized during radial toolpath printing. Here, we report a facile strategy to overcome the existing challenges of cementitious material non-homogeneity by rationally developing new nozzle geometries that passively compensate the differential deposition rate encountered in conventional rectangular nozzles. Using two-phase numerical study, we showed that our strategy has the potential of achieving a homogeneous mass distribution even when the nozzle travel speed is unfavorably high, while filament from a rectangular nozzle remains highly non-homogenous. The material distribution unevenness can be reduced from 1.35 to 1.23 and to 0.98 after adopting trapezoid and gaussian nozzles, indicating improvements of 34.3% and 94.2%, respectively. This work not only outlines the methodology for improving the quality of corner/curved features in 3DCMP, but also introduces a new strategy which can be adopted for other extrusion-based fabrication techniques with high material inertia.

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Birosz, Márton Tamás, Mátyás Andó et Ferenc Safranyik. « Layer Adhesion Test of Additively Manufactured Pins : A Shear Test ». Polymers 14, n^o 1 (24 décembre 2021) : 55. http://dx.doi.org/10.3390/polym14010055.

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Additive Manufacturing (AM) became a popular engineering solution not only for Rapid Prototyping (RP) as a part of product development but as an effective solution for producing complex geometries as fully functional components. Even the modern engineering tools, such as the different simulation software, have a shape optimization solution especially for parts created by AM. To extend the application of these methods in this work, the failure properties of the 3D-printed parts have been investigated via shear test measurements. The layer adhesion can be calculated based on the results, which can be used later for further numerical modeling. In conclusion, it can be stated that the layer formation and the structure of the infill have a great influence on the mechanical properties. The layers formed following the conventional zig-zag infill style show a random failure, and the layers created via extruded concentric circles show more predictable load resistance.

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Hu, Fuwen, et Tian Li. « An Origami Flexiball-Inspired Metamaterial Actuator and Its In-Pipe Robot Prototype ». Actuators 10, n^o 4 (26 mars 2021) : 67. http://dx.doi.org/10.3390/act10040067.

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Usually, polyhedra are viewed as the underlying constructive cells of packing or tiling in many disciplines, including crystallography, protein folding, viruses structure, building architecture, etc. Here, inspired by the flexible origami polyhedra (commonly called origami flexiballs), we initially probe into their intrinsic metamaterial properties and robotized methods from fabrication to actuation. Firstly, the topology, geometries and elastic energies of shape shifting are analyzed for the three kinds of origami flexiballs with extruded outward rhombic faces. Provably, they meet the definitions of reconfigurable and transformable metamaterials with switchable stiffness and multiple degrees of freedom. Secondly, a new type of soft actuator with rhombic deformations is successfully put forward, different from soft bionic deformations like elongating, contracting, bending, twisting, spiraling, etc. Further, we redesign and fabricate the three-dimensional (3D) printable structures of origami flexiballs considering their 3D printability and foldability, and magnetically actuated them through the attachment of magnetoactive elastomer. Lastly, a fully soft in-pipe robot prototype is presented using the origami flexiball as an applicable attempt. Experimental work clearly suggests that the presented origami flexiball robot has good adaptability to various pipe sizes, and also can be easily expanded to different scales, or reconfigured into more complex metastructures by assembly. In conclusion, this research provides a newly interesting and illuminating member for the emerging families of mechanical metamaterials, soft actuators and soft robots.

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Shojaie, Fatemeh, Carmen Ferrero et Isidoro Caraballo. « Development of 3D-Printed Bicompartmental Devices by Dual-Nozzle Fused Deposition Modeling (FDM) for Colon-Specific Drug Delivery ». Pharmaceutics 15, n^o 9 (21 septembre 2023) : 2362. http://dx.doi.org/10.3390/pharmaceutics15092362.

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Dual-nozzle fused deposition modeling (FDM) is a 3D printing technique that allows for the simultaneous printing of two polymeric filaments and the design of complex geometries. Hence, hybrid formulations and structurally different sections can be combined into the same dosage form to achieve customized drug release kinetics. The objective of this study was to develop a novel bicompartmental device by dual-nozzle FDM for colon-specific drug delivery. Hydroxypropylmethylcellulose acetate succinate (HPMCAS) and polyvinyl alcohol (PVA) were selected as matrix-forming polymers of the outer pH-dependent and the inner water-soluble compartments, respectively. 5-Aminosalicylic acid (5-ASA) was selected as the model drug. Drug-free HPMCAS and drug-loaded PVA filaments suitable for FDM were extruded, and their properties were assessed by thermal, X-ray diffraction, microscopy, and texture analysis techniques. 5-ASA (20% w/w) remained mostly crystalline in the PVA matrix. Filaments were successfully printed into bicompartmental devices combining an outer cylindrical compartment and an inner spiral-shaped compartment that communicates with the external media through an opening. Scanning electron microscopy and X-ray tomography analysis were performed to guarantee the quality of the 3D-printed devices. In vitro drug release tests demonstrated a pH-responsive biphasic release pattern: a slow and sustained release period (pH values of 1.2 and 6.8) controlled by drug diffusion followed by a faster drug release phase (pH 7.4) governed by polymer relaxation/erosion. Overall, this research demonstrates the feasibility of the dual-nozzle FDM technique to obtain an innovative 3D-printed bicompartmental device for targeting 5-ASA to the colon.

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Papon, Easir Arafat, Anwarul Haque et Muhammad Ali Rob Sharif. « Numerical study for the improvement of bead spreading architecture with modified nozzle geometries in additive manufacturing of polymers ». Rapid Prototyping Journal 27, n^o 3 (4 février 2021) : 518–29. http://dx.doi.org/10.1108/rpj-05-2019-0142.

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Purpose This paper aims to develop a numerical model of bead spreading architecture of a viscous polymer in fused filament fabrication (FFF) process with different nozzle geometry. This paper also focuses on the manufacturing feasibility of the nozzles and 3D printing of the molten beads using the developed nozzles. Design/methodology/approach The flow of a highly viscous polymer from a nozzle, the melt expansion in free space and the deposition of the melt on a moving platform are captured using the FLUENT volume of fluid (VOF) method based computational fluid dynamics code. The free surface motion of the material is captured in VOF, which is governed by the hydrodynamics of the two-phase flow. The phases involved in the numerical model are liquid polymer and air. A laminar, non-Newtonian and non-isothermal flow is assumed. Under such assumptions, the spreading characteristic of the polymer is simulated with different nozzle-exit geometries. The governing equations are solved on a regular stationary grid following a transient algorithm, where the boundary between the polymer and the air is tracked by piecewise linear interface construction (PLIC) to reconstruct the free surface. The prototype nozzles were also manufactured, and the deposition of the molten beads on a flatbed was performed using a commercial 3D printer. The deposited bead cross-sections were examined through optical microscopic examination, and the cross-sectional profiles were compared with those obtained in the numerical simulations. Findings The numerical model successfully predicted the spreading characteristics and the cross-sectional shape of the extruded bead. The cross-sectional shape of the bead varied from elliptical (with circular nozzle) to trapezoidal (with square and star nozzles) where the top and bottom surfaces are significantly flattened (which is desirable to reduce the void spaces in the cross-section). The numerical model yielded a good approximation of the bead cross-section, capturing most of the geometric features of the bead with a reasonable qualitative agreement compared to the experiment. The quantitative comparison of the cross-sectional profiles against experimental observation also indicated a favorable agreement. The significant improvement observed in the bead cross-section with the square and star nozzles is the flattening of the surfaces. Originality/value The developed numerical algorithm attempts to address the fundamental challenge of voids and bonding in the FFF process. It presents a new approach to increase the inter-bead bonding and reduce the inter-bead voids in 3D printing of polymers by modifying the bead cross-sectional shape through the modification of nozzle exit-geometry. The change in bead cross-sectional shape from elliptical (circular) to trapezoidal (square and star) cross-section is supposed to increase the contact surface area and inter-bead bonding while in contact with adjacent beads.

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Drossel, Welf-Guntram, Jörn Ihlemann, Ralf Landgraf, Erik Oelsch et Marek Schmidt. « Basic Research for Additive Manufacturing of Rubber ». Polymers 12, n^o 10 (1 octobre 2020) : 2266. http://dx.doi.org/10.3390/polym12102266.

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The dissemination and use of additive processes are growing rapidly. Nevertheless, for the material class of elastomers made of vulcanizable rubber, there is still no technical solution for producing them using 3D printing. Therefore, this paper deals with the basic investigations to develop an approach for rubber printing. For this purpose, a fused deposition modeling (FDM) 3D printer is modified with a screw extruder. Tests are carried out to identify the optimal printing parameters. Afterwards, test prints are performed for the deposition of rubber strands on top of each other and for the fabrication of simple two-dimensional geometries. The material behavior during printing, the printing quality as well as occurrences of deviations in the geometries are evaluated. The results show that the realization of 3D rubber printing is possible. However, there is still a need for research to stabilize the layers during the printing process. Additionally, further studies are necessary to determine the optimum parameters for traverse speed and material discharge, especially on contours.

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Goh, Wei, et Michinao Hashimoto. « Dual Sacrificial Molding : Fabricating 3D Microchannels with Overhang and Helical Features ». Micromachines 9, n^o 10 (16 octobre 2018) : 523. http://dx.doi.org/10.3390/mi9100523.

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Fused deposition modeling (FDM) has become an indispensable tool for 3D printing of molds used for sacrificial molding to fabricate microfluidic devices. The freedom of design of a mold is, however, restricted to the capabilities of the 3D printer and associated materials. Although FDM has been used to create a sacrificial mold made with polyvinyl alcohol (PVA) to produce 3D microchannels, microchannels with free-hanging geometries are still difficult to achieve. Herein, dual sacrificial molding was devised to fabricate microchannels with overhang or helical features in PDMS using two complementary materials. The method uses an FDM 3D printer equipped with two extruders and filaments made of high- impact polystyrene (HIPS) and PVA. HIPS was initially removed in limonene to reveal the PVA mold harboring the design of microchannels. The PVA mold was embedded in PDMS and subsequently removed in water to create microchannels with 3D geometries such as dual helices and multilayer pyramidal networks. The complementary pairing of the HIPS and PVA filaments during printing facilitated the support of suspended features of the PVA mold. The PVA mold was robust and retained the original design after the exposure to limonene. The resilience of the technique demonstrated here allows us to create microchannels with geometries not attainable with sacrificial molding with a mold printed with a single material.

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Shuaibu, A., et A. Ahmad. « Effects of heat treatment on tensile properties of 3D-printed short fiber-reinforced composites ». Nigerian Journal of Technology 43, n^o 1 (12 avril 2024) : 56–63. http://dx.doi.org/10.4314/njt.v43i1.8.

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3D-printed carbon fibre-reinforced composites (CFRC) using fused deposition modelling (FDM) offer the potential for building complex geometries and low waste. However, these composites have weaker interlaminar bonding and higher void content than traditional composites. This paper explores the effect of temperature on improving the mechanical properties of 3D-printed short carbon fibre- reinforced polyamide (PACF). Two types of printed structures were tested: one with a 0° build orientation (parallel to extruder movement) and the other with a 90° build orientation (perpendicular to extruder movement). Both samples were heat-treated at 150°C. Force vs. displacement data was obtained from the MTS testing machine. After that, the tested samples were viewed under an optical microscope. Images obtained from the optical microscope are then analyzed to see how the samples failed by checking the microstructure. The average ultimate strength, ultimate strain, and elastic modulus were used for the analysis. The sample follows a trend where the strength and elastic modulus increase after heat treatment. The result also showed that the 0° build orientation samples have higher mechanical performance than the 90° build orientation sample. Also, from the ultimate strain values, it was evident that samples printed in the 0° absorbed more energy, exhibiting 83% higher resistance before final failure. Lastly, an optical microscope was used to investigate the failure mechanisms of the samples.

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Brunčko, M., A. C. Kneissl, L. Gorše et I. Anžel. « Characterization of microstructure and magnetic properties of 3D printed bonded magnets made by fused deposition modeling ». Practical Metallography 61, n^o 3 (20 février 2024) : 170–81. http://dx.doi.org/10.1515/pm-2024-0013.

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Abstract Bonded magnets are composite materials consisting of polymer matrix and magnetic powders, prepared by rapid solidification processes from Nd-Fe-B alloys. They are synthesised by the compounding process on a twin-screw extruder, whereby, the finished products of complex shapes can be made from bonded magnets using injection moulding or 3D printing by fused deposition modelling method (FDM). The main advantages of 3D printing are the possibility to produce parts with complex geometries that are not possible with traditional manufacturing techniques and low-cost production of small batches. The aim of the research work was to identify the optimum processing parameters, which would give 3D printed bonded magnets characteristics similar to those produced by injection moulding. The characterization of the microstructure of bonded magnets was made on cryo-fractured, conventionally mechanically prepared and ion beam polished samples. The microstructures of bonded magnets were analysed by stereo, optical and scanning electron microscopy. Additionally, the influence of the 3D printing parameters on the magnetic properties has been examined. The results of the research work have shown that desired magnetic properties of 3D printed bonded magnets can be obtained by optimizing the thickness of the printed layer, printing speed and flowrate. In addition, it was revealed that selection of the materialographic preparation method plays a crucial step for correct microstructural characterization. Namely, the impropriate sample preparation results in artifacts that are mostly misinterpreted as microstructural defects (pores, cracks, non-adherent layers, etc.) accidently caused during 3d printing.

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Reich, Matthew J., Aubrey L. Woern, Nagendra G. Tanikella et Joshua M. Pearce. « Mechanical Properties and Applications of Recycled Polycarbonate Particle Material Extrusion-Based Additive Manufacturing ». Materials 12, n^o 10 (20 mai 2019) : 1642. http://dx.doi.org/10.3390/ma12101642.

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Past work has shown that particle material extrusion (fused particle fabrication (FPF)/fused granular fabrication (FGF)) has the potential for increasing the use of recycled polymers in 3D printing. This study extends this potential to high-performance (high-mechanical-strength and heat-resistant) polymers using polycarbonate (PC). Recycled PC regrind of approximately 25 mm2 was 3D printed with an open-source Gigabot X and analyzed. A temperature and nozzle velocity matrix was used to find useful printing parameters, and a print test was used to maximize the output for a two-temperature stage extruder for PC. ASTM type 4 tensile test geometries as well as ASTM-approved compression tests were used to determine the mechanical properties of PC and were compared with filament printing and the bulk virgin material. The results showed the tensile strength of parts manufactured from the recycled PC particles (64.9 MPa) were comparable to that of the commercial filament printed on desktop (62.2 MPa) and large-format (66.3 MPa) 3D printers. Three case study applications were investigated: (i) using PC as a rapid molding technology for lower melting point thermoplastics, (ii) printed parts for high temperature applications, and (iii) printed parts for high-strength applications. The results show that recycled PC particle-based 3D printing can produce high-strength and heat-resistant products at low costs.

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Golman, Boris, Piotr Skrzypacz et Wittaya Julklang. « Modeling and Numerical Study of Ceramic Paste Extrusion ». MATEC Web of Conferences 333 (2021) : 02011. http://dx.doi.org/10.1051/matecconf/202133302011.

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The extrusion processes of ceramic pastes, including 3D printing, are used for the production of high-value products. Ceramic paste extrusion is a complex process which depends on the paste rheological properties, die and extruder geometries, and operational parameters. Modeling and quantitative analysis of paste molding are important to design proper extrusion process for the production of high-value extrudates of desired strength, shape, and morphology. In this paper, the mathematical model of ram extrusion of ceramic materials is established, and the paste continuity and momentum equations for non-Newtonian fluid based on the modified Herschel-Bulkley viscous model were solved numerically. The effects of die geometry and paste feed rate on the distributions of paste velocity and pressure in the extruder and die were investigated numerically. As a result, the steeper radial profile of longitudinal velocity and higher value of longitudinal velocity were obtained in the narrow die. The pressure significantly increases in the die at a high feed rate, and the pressure profile is almost flat in the barrel. The rate of increase of the maximum pressure decreases with an increase of paste feed rate. The pressure steeply increases in the die of small diameter. The maximum pressure linearly increases with the ratio of die length to diameter.

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Golman, Boris, Piotr Skrzypacz et Wittaya Julklang. « Modeling and Numerical Study of Ceramic Paste Extrusion ». MATEC Web of Conferences 333 (2021) : 02011. http://dx.doi.org/10.1051/matecconf/202133302011.

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The extrusion processes of ceramic pastes, including 3D printing, are used for the production of high-value products. Ceramic paste extrusion is a complex process which depends on the paste rheological properties, die and extruder geometries, and operational parameters. Modeling and quantitative analysis of paste molding are important to design proper extrusion process for the production of high-value extrudates of desired strength, shape, and morphology. In this paper, the mathematical model of ram extrusion of ceramic materials is established, and the paste continuity and momentum equations for non-Newtonian fluid based on the modified Herschel-Bulkley viscous model were solved numerically. The effects of die geometry and paste feed rate on the distributions of paste velocity and pressure in the extruder and die were investigated numerically. As a result, the steeper radial profile of longitudinal velocity and higher value of longitudinal velocity were obtained in the narrow die. The pressure significantly increases in the die at a high feed rate, and the pressure profile is almost flat in the barrel. The rate of increase of the maximum pressure decreases with an increase of paste feed rate. The pressure steeply increases in the die of small diameter. The maximum pressure linearly increases with the ratio of die length to diameter.

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Mazzei Capote, Gerardo Andres, Maria Camila Montoya-Ospina, Zijie Liu, Michael Sabatini Mattei, Boyuan Liu, Aidan P. Delgado, Zongfu Yu, Randall H. Goldsmith et Tim Andreas Osswald. « Compounding a High-Permittivity Thermoplastic Material and Its Applicability in Manufacturing of Microwave Photonic Crystals ». Materials 15, n^o 7 (28 mars 2022) : 2492. http://dx.doi.org/10.3390/ma15072492.

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Additive Manufacturing (AM) techniques allow the production of complex geometries unattainable through other traditional technologies. This advantage lends itself well to rapidly iterating and improving upon the design of microwave photonic crystals, which are structures with intricate, repeating features. The issue tackled by this work involves compounding a high-permittivity material that can be used to produce 3D microwave photonic structures using polymer extrusion-based AM techniques. This material was acrylonitrile butadiene styrene (ABS)-based and used barium titanate (BaTiO3) ceramic as the high-permittivity component of the composite and involved the use of a surfactant and a plasticizer to facilitate processing. Initial small amounts of the material were compounded using an internal batch mixer and studied using polymer thermal analysis techniques, such as thermogravimetric analysis, rheometry, and differential scanning calorimetry to determine the proper processing conditions. The production of the material was then scaled up using a twin-screw extruder system, producing homogeneous pellets. Finally, the thermoplastic composite was used with a screw-based, material extrusion additive manufacturing technique to produce a slab for measuring the relative permittivity of the material, as well as a preliminary 3D photonic crystal. The real part of the permittivity was measured to be 12.85 (loss tangent = 0.046) in the range of 10 to 12 GHz, representing the highest permittivity ever demonstrated for a thermoplastic AM composite at microwave frequencies.

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Khan, Zainab N., Hamed I. Albalawi, Alexander U. Valle-Pérez, Ali Aldoukhi, Noofa Hammad, Elena Herrera-Ponce de León, Sherin Abdelrahman et Charlotte A. E. Hauser. « From 3D printed molds to bioprinted scaffolds : A hybrid material extrusion and vat polymerization bioprinting approach for soft matter constructs ». Materials Science in Additive Manufacturing 1, n^o 1 (28 mars 2022) : 7. http://dx.doi.org/10.18063/msam.v1i1.7.

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Three-dimensional (3D) bioprinting methods vary in difficulty and complexity depending on the application desired and biomaterials used. 3D biofabrication is gaining increased traction with enhanced additive manufacturing technologies. Yet, high print resolution and efficiency for the fabrication of complex constructs still prove to be challenging. An intricate balance between biomaterial composition, machine maneuverability, and extrusion mechanism is required. While soft bioinks are highly desirable when used as a biodegradable scaffold material for tissue and organ fabrication, mechanical stiffness and shape fidelity are often compromised. Alternately, post-printing ultraviolet and chemical crosslinking processes improve fidelity but threaten cell viability. Herein, we propose a hybrid fabrication approach to facilitate 3D bioprinting using soft bioinks with instantaneous gelation properties while maintaining shape fidelity for tissue and organ structures of complex geometries. The approach entails a multi-step “3D Printed Molds to Scaffolds” method, which uses additive manufacturing to create accurate negative support structures for the desired construct. A tissue or organ model is first designed in computer-aided design (CAD) modeling software to create a negative mold structure of the desired tissue or organ. Using a Formlabs® SLA 3D printer, the negative mold is fabricated at desired scale using a biocompatible elastic resin. Then, a robotic 3D bioprinting system is loaded with a sliced g-code of the CAD model. The robot start position is aligned with the placement of the fabricated mold on the printbed. Microfluidic pumps deliver three solutions through a customized nozzle to extrude peptide bioink, which gels instantaneously. The initial layers of the structure are formed within the mold to create a solid foundation of the construct. The hybrid approach was found to enhance fidelity considerably and enabled the printing of a complex human ear structure. It is promising for tissue and organ fabrication as it offers a cost-effective support structure without increasing printing time. It could also be used as a rapid prototyping approach for researchers who do not have access to 3D bioprinting systems. Biofabrication, from printed molds to bioprinted scaffolds, will potentially enhance the printing experience with soft bioinks while preserving cell durability and viability. 

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Costanza, Girolamo, Angelo Del Ferraro et Maria Elisa Tata. « Experimental Set-Up of the Production Process and Mechanical Characterization of Metal Foams Manufactured by Lost-PLA Technique with Different Cell Morphology ». Metals 12, n^o 8 (20 août 2022) : 1385. http://dx.doi.org/10.3390/met12081385.

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A flexible and versatile method for manufacturing open-cell metal foams, called lost-PLA, is presented in this work. With a double extruder 3D printer (FDM, Ultimaker S3, Utrecht, The Netherlands), it is possible to make polymer-based samples of the lost model. Through CAD modeling, different geometries were replicated so as to get black PLA samples. This method combines the advantages of rapid prototyping with the possibility of manufacturing Al-alloy specimens with low time to market. The production process is articulated in many steps: PLA foams are inserted into an ultra-resistant plaster mix, after which the polymer is thermally degraded. The next step consists of the gravity casting of the EN-6082 alloy in the plaster form, obtaining metal foams that are interesting from a technological point of view as well as with respect to their mechanical properties. These foam prototypes can find application in the automotive, civil and aeronautical fields due to their high surface/weight ratio, making them optimal for heat exchange and for the ability to absorb energy during compression. The main aspects on which we focus are the set-up of the process parameters and the characterization of the mechanical properties of the manufactured samples. The main production steps are examined at first. After that, the results obtained for mechanical performance during static compression tests with different geometry porosities are compared and discussed. The foam with truncated octahedron cells was found to show the highest absorbed energy/relative density ratio.

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Chaurasia, Parul, Richa Singh et Sanjeev Kumar Mahto. « FRESH-based 3D bioprinting of complex biological geometries using chitosan bioink ». Biofabrication, 28 juin 2024. http://dx.doi.org/10.1088/1758-5090/ad5d18.

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Abstract Traditional three-dimensional (3D) bioprinting has always been associated with the challenge of print fidelity of complex geometries due to the gel-like nature of the bioinks. Embedded 3D bioprinting has emerged as a potential solution to print complex geometries using proteins and polysaccharides-based bioinks. This study demonstrated the Freeform Reversible Embedding of Suspended Hydrogels (FRESH) 3D bioprinting method of chitosan bioink to 3D bioprint complex geometries. 4.5% chitosan was dissolved in an alkali solvent to prepare the bioink. Rheological evaluation of the bioink described its shear-thinning nature. The power law equation was fitted to the shear rate-viscosity plot. The flow index value was less than 1, categorizing the material as pseudo-plastic. The chitosan bioink was extruded into another medium, a thermo-responsive 4.5% gelatin hydrogel. This hydrogel provides support to the growing print structures while printing. After this, the 3D bioprinted structure was crosslinked with 60° C water to stabilize the structure. Using this method, we have 3D bioprinted complex biological structures like the human tri-leaflet heart valve, a section of a human right coronary arterial tree, a scale-down outer structure of the human kidney, and a human ear. Additionally, we have shown the mechanical tunability and suturability of the 3D bioprinted structures. This demonstrates the capability of the chitosan bioink and FRESH method for 3D bioprinting of biological models for surgical training and planning.

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Sullivan, Anthony, Anil Saigal et Michael A. Zimmerman. « Structure-property-processing relationships in extruded liquid crystal polymer film ». Polymers and Polymer Composites, 7 avril 2021, 096739112110070. http://dx.doi.org/10.1177/09673911211007019.

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Liquid crystal polymers (LCPs) derive favorable mechanical, chemical, and electrical behavior from long-range molecular ordering. The microstructure gives rise to anisotropic bulk properties that are problematic for industrial applications, and thus the ability to model the polymer directionality is essential to the design of isotropic material manufacturing processes. This investigation proposes a modeling methodology to simulate the 3D director field in full-scale film extrusion geometries. Wide-angle x-ray scattering (WAXS) is used to validate the predicted orientation for a standard coat-hanger die, and is compared with macroscopic mechanical, thermal, and dielectric testing of LCP film to illustrate the morphological dependence of the polymer properties. The highly anisotropic orientation state resulting from cast film extrusion is both predicted by the model and confirmed experimentally, and this preferred orientation is shown to correlate with observed anisotropy in the bulk properties. Additionally, a practical implementation of the modeling tool is presented to simulate directionality in two alternative die geometries designed to improve bulk isotropy, and it is demonstrated that the model is capable of simulating the resulting order for large, irregular domains typical of industrial processing.

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Kodali, Deepa, Chibu O. Umerah, Mohanad O. Idrees, S. Jeelani et Vijaya K. Rangari. « Fabrication and characterization of polycarbonate-silica filaments for 3D printing applications ». Journal of Composite Materials, 2 septembre 2021, 002199832110447. http://dx.doi.org/10.1177/00219983211044748.

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Owing to its robustness, ability to achieve complex geometries, and ease of use, 3D printing has become one of the noteworthy applications in the field of engineering. Polycarbonate has become a thermoplastic of interest due to its excellent mechanical and optical properties. Especially when infused with nanosilica, polycarbonate becomes a potential candidate for 3D printing with enhanced properties. Polycarbonate nanocomposite filaments infused with AEROSIL (nanosilica) have been melt extruded with various filler loadings of 0.5, 1, and 3 wt% and are then 3D printed. The thermal analysis of the filaments has shown that thermal stability of the filaments increases with increase in filler loading. Tensile tests have shown that addition of nanosilica have enhanced the mechanical properties of the filaments as well as 3D printed films. The addition of silica in low concentrations exhibit higher transmittance of UV light, as silica restricts the mobility of polycarbonate. Despite 3D printing causing voids in bulk materials, silica at low concentration (0.5 and 1 wt%) can improve the mechanical and optical properties. These improvements are promising for applications in thin film interfaces and the automotive industry.

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Dávila, José Luis, Bruna Maria Manzini, Marcos Akira d'Ávila et Jorge Vicente Lopes da Silva. « Open-source syringe extrusion head for shear-thinning materials 3D printing ». Rapid Prototyping Journal, 14 mars 2022. http://dx.doi.org/10.1108/rpj-09-2021-0245.

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Purpose This study aims to report the development of an open-source syringe extrusion head for shear-thinning materials. The target is to adapt open-source 3D printers to be helpful in research lines that use gels, hydrogels, pastes, inks, and bio-inks. Design/methodology/approach This hardware was designed to be compatible with a Graber i3-based 3D printer; nevertheless, it can be easily adapted to other open-source 3D printers. Findings The extrusion head successfully deposits the material during the 3D printing process. It was validated fabricating geometries that include scaffold structures, which are a possible application of bioprinting for tissue engineering. As reported, the extruded filaments allowed the porous samples' structuration. Practical implications This system expands the applications of open-source 3D printers used at the laboratory scale. It enables low-cost access to research areas such as tissue engineering and biofabrication, energy storage devices and food 3D printing. Originality/value The open-source hardware here reported is of simple fabrication, assembly and installation. It uses a Cardan coupling and a three guides system to transfer the stepper motor motion. This approach allows continuous movement transfer to the syringe piston, producing an adequate deposition or retraction. Thus, the effect of misalignments is avoided, considering that these latter can cause skipping steps in the motor, directly affecting the deposition.

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Karthikeyan, Leena, Suraj Sudhi, Tushar Shriram Bhatt, Mani Ganesan, Panthaplackal Bhaskaran Soumyamol, Jayalatha Thankarajan, Suchithra Cheriyan et Dona Mathew. « Poly(ether ether ketone)s processed through extrusion-machining and 3D printing : A comparative study on mechanical, thermal and fracture properties at ambient and cryogenic environments ». Journal of Elastomers & ; Plastics, 25 septembre 2020, 009524432096183. http://dx.doi.org/10.1177/0095244320961830.

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Poly Ether Ether Ketone (PEEK) is a very promising engineering thermoplastic material having capability to perform over wide service temperatures from cryogenic to around 300°C. Processing of PEEK is a challenging task, owing to its physical, thermo physical properties and chemical nature. The present paper envisages processing of PEEK by two different techniques viz, 3D printing and extrusion and assessment of properties of respective specimens at 30°C and −196°C. Thermal and mechanical properties and fracture morphological features of PEEK specimen, processed using these techniques are compared. Samples processed by extrusion possessed higher mechanical properties both at 30°C and −196°C. The 3D printed samples, though exhibited inferior strength and modulus, showed significantly higher elongation (150–250%) at 30°C. All samples showed ductile fracture behavior at 30°C. At −196°C, the fracture morphology got transformed in to a pattern typical of brittle materials, as expected. Extruded specimens showed lower thermal expansion coefficient compared to the 3D printed specimens. Thermal expansion characteristics were different in the X, Y and Z directions for 3D printed specimens due to the anisotropy resulting from printing direction which is corroborated by the morphological studies. The results of this investigation enable designing and fabrication of PEEK based structural components of desired geometries for various applications.

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Ovy, S. M. Al Islam, Gianni Stano, Gianluca Percoco, Matteo Cianchetti et Yonas Tadesse. « Inexpensive monolithic additive manufacturing of silicone structures for bio-inspired soft robotic systems ». Engineering Research Express, 23 janvier 2023. http://dx.doi.org/10.1088/2631-8695/acb587.

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Abstract In soft robotics, the fabrication of extremely soft structures capable of performing bio-inspired complex motion is a challenging task. In this paper, an innovative 3D printing of soft silicone structures with embedded shape memory alloy (SMA) actuators are proposed, which is completed in a single printing cycle from CAD files. The proposed custom-made 3D printing setup, based on the material extrusion (MEX) method, was used in conjunction with a cartesian pick and place robot (CPPR) to completely automate the fabrication of thick silicone skins (7 mm) with embedded shape memory alloy actuators. These structures were fabricated monolithically without any assembly tasks and direct human intervention. Taking advantage of the capability to 3D print different geometries, three different patterns were fabricated over the silicone skin, resulting in remarkable dynamic motions: an out-of-plane deformation (jumping of the structure from the x-y plane to the x-z plane) was achieved for the first-time employing silicone skin, to the best of the author’s knowledge. In addition, two process parameters (printing speed and build plate temperature) and the extruded silicone curing mechanisms were investigated to enhance the printing quality. This paper aims to advance the role of additive manufacturing in the field of soft robotics by demonstrating all the benefits that a low-cost, custom-made silicone 3D printer can bring to the table in terms of manufacturing soft bio-inspired structures.

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Schäfke, Florian Patrick, Frederic Timmann, Christian Klose, André Hürkamp, Klaus Dröder et Hans Jürgen Maier. « Development of EN AW-6082 Metal Foams and Stochastic Foam Modeling for the Individualization of Extruded Profiles ». Journal of Materials Engineering and Performance, 20 décembre 2023. http://dx.doi.org/10.1007/s11665-023-09031-9.

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AbstractLightweight design and hybrid components enable innovative and new component concepts, especially when combining structurally reliable metal components with individualized polymer components. In this research, a process for additive manufacturing polymers on the surface of extruded aluminum profiles is examined. The extrusion process is adapted to produce foamable aluminum profiles, which can be utilized to enable a form fit between the two materials and ensures sufficient bond strength. For this purpose, a novel aluminum block material based on the standard wrought alloy EN AW-6082 was developed. It consists of a solid EN AW-6082 core and powder metallurgically produced outer layer, which allows local foaming of the aluminum profile surface. The main objective of this study was to optimize the bond strength of the hybrid aluminum-polymer components. The methods employed include fabricating aluminum test specimens, performing mechanical tests, x-ray microscopy to analyze the pore structure and evaluating the 3D pore distribution and the wall thickness. Virtual foam models were created to numerically investigate suitable pore sizes and foam geometries for form-fit with the polymer. The porosity achieved as a function of the processing of the components are discussed and a comparison is made between the real and virtual pore structures.

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Kim, Jihyun, Seol‐Ha Jeong, Brendan Craig Thibault, Javier Alejandro Lozano Soto, Hiroyuki Tetsuka, Surya Varchasvi Devaraj, Estefania Riestra et al. « Large Scale Ultrafast Manufacturing of Wireless Soft Bioelectronics Enabled by Autonomous Robot Arm Printing Assisted by a Computer Vision‐Enabled Guidance System for Personalized Wound Healing ». Advanced Healthcare Materials, 15 novembre 2024. http://dx.doi.org/10.1002/adhm.202401735.

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AbstractA Customized wound patch for Advanced tissue Regeneration with Electric field (CARE), featuring an autonomous robot arm printing system guided by a computer vision‐enabled guidance system for fast image recognition is introduced. CARE addresses the growing demand for flexible, stretchable, and wireless adhesive bioelectronics tailored for electrotherapy, which is suitable for rapid adaptation to individual patients and practical implementation in a comfortable design. The visual guidance system integrating a 6‐axis robot arm enables scans from multiple angles to provide a 3D map of complex and curved wounds. The size of electrodes and the geometries of power‐receiving coil are essential components of the CARE and are determined by a MATLAB simulation, ensuring efficient wireless power transfer. Three heterogeneous inks possessing different rheological behaviors can be extruded and printed sequentially on the flexible substrates, supporting fast manufacturing of large customized bioelectronic patches. CARE can stimulate wounds up to 10 mm in depth with an electric field strength of 88.8 mV mm−1. In vitro studies reveal the ability to accelerate cell migration by a factor of 1.6 and 1.9 for human dermal fibroblasts and human umbilical vein endothelial cells, respectively. This study highlights the potential of CARE as a clinical wound therapy method to accelerate healing.

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Cai, Betty, David Kilian, Sadegh Ghorbani, Julien Roth, Alexis J. Seymour, Lucia Giulia Brunel, Daniel Ramos Mejia et al. « One-step bioprinting of endothelialized, self-supporting arterial and venous networks ». Biofabrication, 16 janvier 2025. https://doi.org/10.1088/1758-5090/adab26.

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Abstract Advances in biofabrication have enabled the generation of freeform perfusable networks mimicking vasculature. However, key challenges remain in the effective endothelialization of these complex, vascular-like networks, including cell uniformity, seeding efficiency, and the ability to pattern multiple cell types. To overcome these challenges, we present an integrated fabrication and endothelialization strategy to directly generate branched, endothelial cell-lined networks using a diffusion-based, embedded 3D bioprinting process. In this strategy, a gelatin microparticle sacrificial ink delivering both cells and crosslinkers is extruded into a crosslinkable gel precursor support bath. A self-supporting, perfusable structure is formed by diffusion-induced crosslinking, after which the sacrificial ink is melted to allow cell release and adhesion to the printed lumen. This approach produces a uniform cell lining throughout networks with complex branching geometries, which are challenging to uniformly and efficiently endothelialize using conventional perfusion-based approaches. Furthermore, the biofabrication process enables high cell viability (>90%) and the formation of a confluent endothelial layer providing vascular-mimetic barrier function and shear stress response. Leveraging this strategy, we demonstrate for the first time the patterning of multiple endothelial cell types, including arterial and venous cells, within a single arterial-venous-like network. Altogether, this strategy enables the fabrication of multi-cellular engineered vasculature with enhanced geometric complexity and phenotypic heterogeneity.

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Nayak, Vasudev Vivekanand, Vijayavenkataraman Sanjairaj, Rakesh Kumar Behera, James E. Smay, Nikhil Gupta, Paulo G. Coelho et Lukasz Witek. « Direct inkjet writing of polylactic acid/β‐tricalcium phosphate composites for bone tissue regeneration : A proof‐of‐concept study ». Journal of Biomedical Materials Research Part B : Applied Biomaterials 112, n^o 4 (23 mars 2024). http://dx.doi.org/10.1002/jbm.b.35402.

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AbstractThere is an ever‐evolving need of customized, anatomic‐specific grafting materials for bone regeneration. More specifically, biocompatible and osteoconductive materials, that may be configured dynamically to fit and fill defects, through the application of an external stimulus. The objective of this study was to establish a basis for the development of direct inkjet writing (DIW)‐based shape memory polymer‐ceramic composites for bone tissue regeneration applications and to establish material behavior under thermomechanical loading. Polymer‐ceramic (polylactic acid [PLA]/β‐tricalcium phosphate [β‐TCP]) colloidal gels were prepared of different w/w ratios (90/10, 80/20, 70/30, 60/40, and 50/50) through polymer dissolution in acetone (15% w/v). Cytocompatibility was analyzed through Presto Blue assays. Rheological properties of the colloidal gels were measured to determine shear‐thinning capabilities. Gels were then extruded through a custom‐built DIW printer. Space filling constructs of the gels were printed and subjected to thermomechanical characterization to measure shape fixity (Rf) and shape recovery (Rr) ratios through five successive shape memory cycles. The polymer‐ceramic composite gels exhibited shear‐thinning capabilities for extrusion through a nozzle for DIW. A significant increase in cellular viability was observed with the addition of β‐TCP particles within the polymer matrix relative to pure PLA. Shape memory effect in the printed constructs was repeatable up to 4 cycles followed by permanent deformation. While further research on scaffold macro‐/micro‐geometries, and engineered porosities are warranted, this proof‐of‐concept study suggested suitability of this polymer‐ceramic material and the DIW 3D printing workflow for the production of customized, patient specific constructs for bone tissue engineering.

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Tagliavini, Giorgia, Federico Solari et Roberto Montanari. « CFD Simulation of a Co-rotating Twin-screw Extruder : Validation of a Rheological Model for a Starch-Based Dough for Snack Food ». International Journal of Food Engineering 14, n^o 2 (6 septembre 2017). http://dx.doi.org/10.1515/ijfe-2017-0116.

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AbstractThe extrusion of starch-based products has been a matter of interest, especially for the pasta and the snack food production. In recent years, twin-screw extruders for snack food have been studied from both structural and fluid dynamics viewpoints. This project started from the rheological characterization of a starch-based dough (corn 34 wt%, tapioca 32 wt%), comparing viscosity values acquired in laboratory with different theoretical models found in literature. A computational fluid dynamic (CFD) simulation recreating the simple case of a fluid flow between two parallel plates was carried out to validate the former comparison. After the rheological validation was completed, the second phase of this work covered a 3D CFD simulation of the first part of the twin-screw extruder (feeding zone). The objective was to find a suitable model for describing the dough rheological behavior and the operating conditions of a co-rotating intermeshing twin-screw extruder. Once the model would be defined, it would allow to investigate several working conditions and different screws geometries of the machine, predicting the evolution of the product rheological properties.

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Idogava, Henrique Takashi, Daniel Marcos Souza do Couto, Leonardo Santana, Jorge Lino Alves et Zilda Castro Silveira. « AltPrint : new filling and slicing process planning based on deposited material with geometry variation ». Rapid Prototyping Journal, 12 mai 2023. http://dx.doi.org/10.1108/rpj-06-2022-0208.

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Purpose This paper aims to address the development and implementation of “AltPrint,” a slicing algorithm based on a new filling process planning from a variation in the deposited material geometry. AltPrint enables changes in the extruded material flow toward local variations in stiffness. The technical feasibility evaluation was conducted experimentally by fused filament fabrication (FFF) process of snap-fit subjected to a mechanical cyclical test. Design/methodology/approach The methodology is based on the estimation of the parameter E from the mathematical relationships among the variation of the material in the material flow, nozzle geometry and extrusion parameters. Calibration, validation and analysis of the printed specimens were divided into two moments, of which the first refers to the material responses (flexural and dynamic mechanical analysis) and the second involves the analysis of the printed components with localized flow properties (for estimating the response to cyclic loading). Finite element analysis assisted in the comparison of two snap-fit geometries, one traditional and one generated by AltPrint. Finally, three examples of compliant mechanisms were developed to demonstrate the potential of the algorithm in the generation of functional prototypes. Findings The contribution of AltPrint is the variable fill width integrated with the slicing software that varies the print parameters in different regions of the object. The alternative extrusion method based on material rate variation was conceived as an “open software” available in GitHub platform, hence, open manufacturing with initial focus on desktop 3D printer based on FFF. The slicing method provides deposited variable-width segments in an organized and replicable filling strategy, resulting in mechanical properties variations in specific regions of a part. It was implemented and evaluated experimentally and indicated potential applications in parts manufactured by the additive process based on extrusion, which requires local flexibilities. Originality/value This paper presents a new alternative method for application in an open additive manufacturing context, specifically for additive extrusion techniques that enable local variations in the material flow. Its potential for manufacturing functional parts, which require flexibility due to cyclic loading, was demonstrated by fabrication and experimental evaluations of parts made in acrylonitrile butadiene styrene filament. The changes proposed by AltPrint enable geometric modifications in the response of the printed parts. The proposed slicing and filling control of parameters is inserted in a context of design for additive manufacturing and shows great potential in the area of product design.

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Bierach, Christopher, Alexsander Alberts Coelho, Michela Turrin, Serdar Asut et Ulrich Knaack. « Wood-based 3D printing : potential and limitation to 3D print building elements with cellulose & ; lignin ». Architecture, Structures and Construction, 15 mars 2023. http://dx.doi.org/10.1007/s44150-023-00088-7.

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AbstractUnder urgent sustainability targets, the building industry craves for renewable and recyclable biomaterials as cellulose is a fiber; Lignin is a plant-derived low-cost polymer with remarkable properties, yet its valorization is in its infancy. Recent studies have shown potentials to combine cellulose and lignin into a renewable bio-based material for the built environment, with the use of additive manufacturing to allow geometric customization and local control of material. However, previous studies also highlighted crucial issues to be solved. One main challenge is the lack of knowledge on combinations of lignin and cellulose with different binders to achieve a paste suitable for 3D printing, leading to a material applicable in the built environment. To contribute overcoming the challenge, this research aimed to explore various combinations of cellulose, lignin, and binders and to study the extrudability of the resulting paste using a clay extruder installed on a robotic arm. Several combinations were explored, evaluated, and compared. The four recipes with the highest scores were used to produce samples for tensile and three-point bending tests, water absorption and retention tests, and microscope analysis. The overall outcome has shown similarities between the mechanical properties of the mixture developed using methylcellulose as the binding agent and rigid polymer foams, such as the ones commonly used as insulation panels. Moreover, the material mix with the highest score in the preliminary assessment was further applied to fabricate samples with varied geometries to assess its potential and limitations combined with the fabrication process. Finally, two demonstrators were produced to explore the printing process for different geometric configurations: conceptual window frame and structural node were designed, and 3D printed as proof of concept.

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Ehrler, Julian, Julian Kattinger, Mike Kornely et Marc Kreutzbruck. « Inline CT-Analysis of the Melting Area during Fused Filament Fabrication ». e-Journal of Nondestructive Testing 29, n^o 6 (juin 2024). http://dx.doi.org/10.58286/29922.

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In the 21st century, 3D printing has become a mainstream process for prototyping and low-volume production. Fused Filament Fabrication is the most commonly used process for 3D printing plastics. A plastic filament is melted in a nozzle and a component is built up layer by layer. As with all manufacturing processes, there is an interest in continuously optimizing and improving the FFF process. One approach is based on process simulation, which provides a better understanding of the process. Subsequently, it is always necessary to validate the simulation models with the real process. This validation has only been possible to a limited extent in the case of FFF. In this work, a method is presented that allows a non-destructive investigation of the melt behaviour during the printing process. For this purpose, a 3D printer nozzle with an extruder was integrated into an X-ray computed tomography system. Thus, a computed tomography scan can be performed during the extrusion process. By using highly absorbent tungsten filaments, sufficient contrast can be created between the metal nozzle and the plastic filament to allow analysis of the melt behaviour. This setup makes it possible to distinguish between the solid filament area and the melt area, as well as to determine the contact between the filament and the die wall. In doing so, simulations can be validated and nozzle geometries can be improved.

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Ehrler, Julian, Mike Kornely, Julian Kattinger, Marc Kreutzbruck et Christian Bonten. « CT-Analysis of the Melting Area in the Fused Filament Fabrication Process ». Research and Review Journal of Nondestructive Testing 1, n^o 1 (août 2023). http://dx.doi.org/10.58286/28063.

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3D printing has established itself in the 21st century as the process for producing prototypes and very small series. In the plastics sector, the fused filament fabrication (FFF) process is used in particular. A plastic filament is melted in a nozzle and a component is built up layer by layer. As with all manufacturing processes, there is an interest in continuously optimizing and improving the FFF process. One possibility is based on process simulations, which enable a better understanding of the entire process. Afterwards a validation of the simulation with the real process is always necessary. In the case of FFF, this validation was so far only possible to a limited extent. In this work, a method is presented that enables a non-destructive investigation of the melting behavior during the printing process. For this purpose, a 3D printer nozzle with an extruder was integrated into an X-ray computed tomography system. Thus, a computed tomography scan (CT scan) can be performed during the extrusion process. By using filaments with high absorbent tungsten, a sufficient contrast can be created between the metal nozzle and the plastic filament, which allows an analysis of the melting behavior. This setup allows to distinguish between the solid filament area and the melt area, as well as to determine contact between the filament and the nozzle wall. In this way, the simulations can be validated and nozzle geometries to be improved in the future by means of improved simulation tools.

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Curmi, Albert, Arif Rochman et Alfred Gatt. « Screw extrusion additive manufacturing of thermoplastic polyolefin elastomer ». Progress in Additive Manufacturing, 15 juin 2024. http://dx.doi.org/10.1007/s40964-024-00696-9.

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AbstractThis study determined the requisite process parameters for good-quality screw extrusion additive manufacturing (AM) of thermoplastic polyolefin (TPO) using fused granulate fabrication (FGF). TPO is a non-hygroscopic, cheaper, and less dense alternative to the well-established thermoplastic polyurethane (TPU). TPO was found to extrude correctly at 170 °C, on a glass build plate at 80 °C with Magigoo PP adhesive. A water uptake test on TPO reported a mass gain plateau of 0.25%, which is significantly lower than that of TPU, which suggests that TPO may not require drying before 3D printing. Tensile testing on FGF TPO specimens achieved similar stress at yield as well as stress and strain at break as indicated by the data sheet for the XY and YZ orientations. The Z direction is significantly weaker than the X and Y orientations, reaching only 30% of the stress at break. TPO achieved the best average stress at yield of 6.36 MPa using the 0.4 mm nozzle with XY printing orientation and stress and strain at break of 13.8 MPa and 1300% at YZ orientation and 1 mm nozzle. The setup achieved relatively high-quality prints of complex geometries, including the popular torture-test Benchy and a child-sized orthotic insole.

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Mele, Mattia, Michele Ricciarelli et Giampaolo Campana. « 3D printing of clay paste enhanced by scrap polymer from powder bed processes ». Rapid Prototyping Journal ahead-of-print, ahead-of-print (2 septembre 2021). http://dx.doi.org/10.1108/rpj-07-2020-0179.

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Purpose Powder bed additive manufacturing processes are widespread due to their many technical and economic advantages. Nevertheless, the disposal of leftover powder poses a problem in terms of process sustainability. The purpose of this paper is to provide an alternative solution to recycle waste PA12 powder from HP multi jet fusion. In particular, the opportunity to use this material as a dispersion in three-dimensional (3D) printed clay is investigated. Design/methodology/approach A commercial fused deposition modelling printer was re-adapted to extrude a viscous paste composed of clay, PA12 and water. Once printed, parts were dried and then put in an oven to melt the polymer fraction. Four compositions with different PA12 concentration were studied. First, the extrudability of the paste was observed by testing different extrusion lengths. Then, the surface porosities were evaluated through microscopical observations of the manufactured parts. Finally, benchmarks with different geometries were digitalised via 3D scanning to analyse the dimensional alterations arising at each stage of the process. Findings Overall, the feasibility of the process is demonstrated. Extrusion tests revealed that the composition of the paste has a minor influence on the volumetric flow rate, exhibiting a better consistency in the case of long extrusions. The percentage of surface cavities was proportional to the polymer fraction contained in the mix. From dimensional analyses, it was possible to conclude that PA12 reduced the degree of shrinkage during the drying phase, while it increased dimensional alterations occurring in the melting phase. The results showed that the dimensional error measured on the z-axis was always higher than that of the XY plane. Practical implications The method proposed in this paper provides an alternative approach to reuse leftover powders from powder bed fusion processes via another additive manufacturing process. This offers an affordable and open-source solution to companies dealing with polymer powder bed fusion, allowing them to reduce their environmental impacts while expanding their production. Originality/value The paper presents an innovative additive manufacturing solution for powder reuse. Unlike the recycling methods in the body of literature, this solution does not require any intermediate transformation process, such as filament fabrication. Also, the cold material deposition enables the adoption of very inexpensive extrusion equipment. This preliminary study demonstrates the feasibility and the benefits of this process, paving the way for numerous future studies.

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