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1
Ferreira, Isaac, Margarida Machado, Fernando Alves und António Torres Marques. „A review on fibre reinforced composite printing via FFF“. Rapid Prototyping Journal 25, Nr. 6 (08.07.2019): 972–88. http://dx.doi.org/10.1108/rpj-01-2019-0004.
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Purpose In industry, fused filament fabrication (FFF) offers flexibility and agility by promoting a reduction in costs and in the lead-time (i.e. time-to-market). Nevertheless, FFF parts exhibit some limitations such as lack of accuracy and/or lower mechanical performance. As a result, some alternatives have been developed to overcome some of these restrictions, namely, the formulation of high performance polymers, the creation of fibre-reinforced materials by FFF process and/or the design of new FFF-based technologies for printing composite materials. This work aims to analyze these technologies. Design/methodology/approach This work aims to study and understand the advances in the behaviour of 3D printed parts with enhanced performance by its reinforcement with several shapes and types of fibres from nanoparticles to continuous fibre roving. Thus, a comprehensive survey of significant research studies carried out regarding FFF of fibre-reinforced thermoplastics is provided, giving emphasis to the most relevant and innovative developments or adaptations undergone at hardware level and/or on the production process of the feedstock. Findings It is shown that the different types of reinforcement present different challenges for the printing process with different outcomes in the part performance. Originality/value This review is focused on joining the most important researches dedicated to the process of FFF-printed parts with different types reinforcing materials. By dividing the reinforcements in categories by shape/geometry and method of processing, it is possible to better quantify performance improvements.
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Li, Yongxiang, Wei Zhao, Qiushi Li, Tongcai Wang und Gong Wang. „In-Situ Monitoring and Diagnosing for Fused Filament Fabrication Process Based on Vibration Sensors“. Sensors 19, Nr. 11 (06.06.2019): 2589. http://dx.doi.org/10.3390/s19112589.
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Fused filament fabrication (FFF) is one of the most widely used additive manufacturing (AM) technologies and it has great potential in fabricating prototypes with complex geometry. For high quality manufacturing, monitoring the products in real time is as important as maintaining the FFF machine in the normal state. This paper introduces an approach that is based on the vibration sensors and data-driven methods for in-situ monitoring and diagnosing the FFF process. The least squares support vector machine (LS-SVM) algorithm has been applied for identifying the normal and filament jam states of the FFF machine, besides fault diagnosis in real time. The identification accuracy for the case studies explored here using LS-SVM is greater than 90%. Furthermore, to ensure the product quality during the FFF process, the back-propagation neural network (BPNN) algorithm has been used to monitor and diagnose the quality defects, as well as the warpage and material stack caused by abnormal leakage for the products in-situ. The diagnosis accuracy for the case studies explored here using BPNN is greater than 95%. Results from the experiments show that the proposed approach can accurately recognize the machine failures and quality defects during the FFF process, thus effectively assuring the product quality.
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Mashayekhi, Fatemeh, Julien Bardon, Vincent Berthé, Henri Perrin, Stephan Westermann und Frédéric Addiego. „Fused Filament Fabrication of Polymers and Continuous Fiber-Reinforced Polymer Composites: Advances in Structure Optimization and Health Monitoring“. Polymers 13, Nr. 5 (04.03.2021): 789. http://dx.doi.org/10.3390/polym13050789.
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3D printed neat thermoplastic polymers (TPs) and continuous fiber-reinforced thermoplastic composites (CFRTPCs) by fused filament fabrication (FFF) are becoming attractive materials for numerous applications. However, the structure of these materials exhibits interfaces at different scales, engendering non-optimal mechanical properties. The first part of the review presents a description of these interfaces and highlights the different strategies to improve interfacial bonding. The actual knowledge on the structural aspects of the thermoplastic matrix is also summarized in this contribution with a focus on crystallization and orientation. The research to be tackled to further improve the structural properties of the 3D printed materials is identified. The second part of the review provides an overview of structural health monitoring technologies relying on the use of fiber Bragg grating sensors, strain gauge sensors and self-sensing. After a brief discussion on these three technologies, the needed research to further stimulate the development of FFF is identified. Finally, in the third part of this contribution the technology landscape of FFF processes for CFRTPCs is provided, including the future trends.
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Dyachenko, E. A., M. Yu Kozenko, A. M. Makarov und A. V. Vaganov. „ANALYSIS OF EXISTING KINEMATICS OF FFF / FDM 3D PRINTERS“. IZVESTIA VOLGOGRAD STATE TECHNICAL UNIVERSITY, Nr. 1(248) (27.01.2021): 57–60. http://dx.doi.org/10.35211/1990-5297-2021-1-248-57-60.
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A comparison of the kinematics used in additive technologies is carried out in order to determine their advantages and disadvantages. The most promising kinematics will be used to create a laboratory stand based on it.
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Honigmann, Philipp, Neha Sharma, Brando Okolo, Uwe Popp, Bilal Msallem und Florian M. Thieringer. „Patient-Specific Surgical Implants Made of 3D Printed PEEK: Material, Technology, and Scope of Surgical Application“. BioMed Research International 2018 (2018): 1–8. http://dx.doi.org/10.1155/2018/4520636.
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Additive manufacturing (AM) is rapidly gaining acceptance in the healthcare sector. Three-dimensional (3D) virtual surgical planning, fabrication of anatomical models, and patient-specific implants (PSI) are well-established processes in the surgical fields. Polyetheretherketone (PEEK) has been used, mainly in the reconstructive surgeries as a reliable alternative to other alloplastic materials for the fabrication of PSI. Recently, it has become possible to fabricate PEEK PSI with Fused Filament Fabrication (FFF) technology. 3D printing of PEEK using FFF allows construction of almost any complex design geometry, which cannot be manufactured using other technologies. In this study, we fabricated various PEEK PSI by FFF 3D printer in an effort to check the feasibility of manufacturing PEEK with 3D printing. Based on these preliminary results, PEEK can be successfully used as an appropriate biomaterial to reconstruct the surgical defects in a “biomimetic” design.
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Jiang, Yong, Michael E. Miller, Marcia E. Hansen, Marcus N. Myers und P. Stephen Williams. „Fractionation and size analysis of magnetic particles using FFF and SPLITT technologies“. Journal of Magnetism and Magnetic Materials 194, Nr. 1-3 (April 1999): 53–61. http://dx.doi.org/10.1016/s0304-8853(98)00577-0.
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Moretti, Michele, Federico Bianchi und Nicola Senin. „Towards the development of a smart fused filament fabrication system using multi-sensor data fusion for in-process monitoring“. Rapid Prototyping Journal 26, Nr. 7 (26.06.2020): 1249–61. http://dx.doi.org/10.1108/rpj-06-2019-0167.
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Purpose This paper aims to illustrate the integration of multiple heterogeneous sensors into a fused filament fabrication (FFF) system and the implementation of multi-sensor data fusion technologies to support the development of a “smart” machine capable of monitoring the manufacturing process and part quality as it is being built. Design/methodology/approach Starting from off-the-shelf FFF components, the paper discusses the issues related to how the machine architecture and the FFF process itself must be redesigned to accommodate heterogeneous sensors and how data from such sensors can be integrated. The usefulness of the approach is discussed through illustration of detectable, example defects. Findings Through aggregation of heterogeneous in-process data, a smart FFF system developed upon the architectural choices discussed in this work has the potential to recognise a number of process-related issues leading to defective parts. Research limitations/implications Although the implementation is specific to a type of FFF hardware and type of processed material, the conclusions are of general validity for material extrusion processes of polymers. Practical implications Effective in-process sensing enables timely detection of process or part quality issues, thus allowing for early process termination or application of corrective actions, leading to significant savings for high value-added parts. Originality/value While most current literature on FFF process monitoring has focused on monitoring selected process variables, in this work a wider perspective is gained by aggregation of heterogeneous sensors, with particular focus on achieving co-localisation in space and time of the sensor data acquired within the same fabrication process. This allows for the detection of issues that no sensor alone could reliably detect.
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Dizon, John Ryan Cortez, Arnaldo D. Valino, Lucio R. Souza, Alejandro H. Espera, Qiyi Chen und Rigoberto C. Advincula. „3D Printed Injection Molds Using Various 3D Printing Technologies“. Materials Science Forum 1005 (August 2020): 150–56. http://dx.doi.org/10.4028/www.scientific.net/msf.1005.150.
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This paper explores the possibility of using different 3d printing methods and materials in the production of polymer molds for injection molding applications. A mold producing a cube was designed using a commercial software. Following the standard 3d printing process, injection molds which could produce a cube were printed using different 3d printing materials and 3d printing technologies. The 3d printing technologies used were Stereolithography (SLA), Polyjet and Fused Filament Fabrication (FFF). A bench-top injection molding machine was used to inject polylactic acid (PLA) in these molds. The quality of the injected parts in terms of dimensional accuracy has been investigated. In some cases, the damage mechanism of the polymer molds has also been observed.
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Gradwohl, Marion, Feng Chai, Julien Payen, Pierre Guerreschi, Philippe Marchetti und Nicolas Blanchemain. „Effects of Two Melt Extrusion Based Additive Manufacturing Technologies and Common Sterilization Methods on the Properties of a Medical Grade PLGA Copolymer“. Polymers 13, Nr. 4 (14.02.2021): 572. http://dx.doi.org/10.3390/polym13040572.
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Although bioabsorbable polymers have garnered increasing attention because of their potential in tissue engineering applications, to our knowledge there are only a few bioabsorbable 3D printed medical devices on the market thus far. In this study, we assessed the processability of medical grade Poly(lactic-co-glycolic) Acid (PLGA)85:15 via two additive manufacturing technologies: Fused Filament Fabrication (FFF) and Direct Pellet Printing (DPP) to highlight the least destructive technology towards PLGA. To quantify PLGA degradation, its molecular weight (gel permeation chromatography (GPC)) as well as its thermal properties (differential scanning calorimetry (DSC)) were evaluated at each processing step, including sterilization with conventional methods (ethylene oxide, gamma, and beta irradiation). Results show that 3D printing of PLGA on a DPP printer significantly decreased the number-average molecular weight (Mn) to the greatest extent (26% Mn loss, p < 0.0001) as it applies a longer residence time and higher shear stress compared to classic FFF (19% Mn loss, p < 0.0001). Among all sterilization methods tested, ethylene oxide seems to be the most appropriate, as it leads to no significant changes in PLGA properties. After sterilization, all samples were considered to be non-toxic, as cell viability was above 70% compared to the control, indicating that this manufacturing route could be used for the development of bioabsorbable medical devices. Based on our observations, we recommend using FFF printing and ethylene oxide sterilization to produce PLGA medical devices.
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Ahroni, Y., N. Dresler, A. Ulanov, D. Ashkenazi, M. Aviv, M. Librus und A. Stern. „Selected Applications of Stimuli-Responsive Polymers: 4D Printing by the Fused Filament Fabrication Technology“. Annals of Dunarea de Jos University of Galati Fascicle XII Welding Equipment and Technology 31 (28.12.2020): 13–22. http://dx.doi.org/10.35219/awet.2020.02.
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In the past few years four-dimensional (4D) printing technologies have attained worldwide interest and they are now considered the "next big thing". The aim of this research is to provide three selected examples of stimuli-responsive polymer (SRP) applications additively manufactured (AM) by the fused filament fabrication (FFF) technique. To that end, a CCT BLUE filament of thermo-responsive polymer was chosen to produce a water temperature indicator, which changes colour from blue to white when temperature increases; a CCU RED filament of photo-responsive polymer was used to produce a sunlight / UV indicator bracelet; a transparent PLA CLEAR polymer, a CCU RED photo-responsive polymer, and an electrical conductive PLA polymer were selected to produce a smart business card stand. The temperature indicator capability was analysed based on examining colour changes as a function of temperature changes. The sunlight/UV indicator capability was analysed based on the inspection of colour change as a function of absorbed sun/ultraviolet light. The electrical conductivity of the conductive PLA polymer was examined by performing resistance measurements. All three objects were successfully produced and their functionality was demonstrated. We hope that these examples will catalyse the expansion of FFF 4D printed SRP applications, as much work remains to be done in designing the parts and developing FFF printing parameters that take advantage of the stimuli-responsive materials currently being developed for FFF technology.
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Grigore, Lucian Stefanita, Amado-George Stefan, Octavian Orban und Ioana-Raluca Adochiei. „Considerations on the Plastic Structure of a UAV Payload Made by 3D Printing Technology“. Materiale Plastice 57, Nr. 4 (06.01.2021): 21–33. http://dx.doi.org/10.37358/mp.20.4.5403.
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With the development of unmanned aerial vehicle (UAV) systems for a multitude of real-time applications, 3D printing technologies have been developed to make thermoplastic structures by fusing filament Fused Deposition Modeling (FDM) or Fused Filament Fabrication (FFF). However, we consider that the realization of new technologies of experimental models / technological demonstrators / prototypes becomes profitable by using 3D printing technologies. The main aim of the paper is to highlight how the use of three types of materials, which are processed differently, influences the Von Mises stresses of the payload used for a UAV, with the mission of photographing and filming from high altitude.
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Dickson, Andrew N., Hisham M. Abourayana und Denis P. Dowling. „3D Printing of Fibre-Reinforced Thermoplastic Composites Using Fused Filament Fabrication—A Review“. Polymers 12, Nr. 10 (24.09.2020): 2188. http://dx.doi.org/10.3390/polym12102188.
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Three-dimensional (3D) printing has been successfully applied for the fabrication of polymer components ranging from prototypes to final products. An issue, however, is that the resulting 3D printed parts exhibit inferior mechanical performance to parts fabricated using conventional polymer processing technologies, such as compression moulding. The addition of fibres and other materials into the polymer matrix to form a composite can yield a significant enhancement in the structural strength of printed polymer parts. This review focuses on the enhanced mechanical performance obtained through the printing of fibre-reinforced polymer composites, using the fused filament fabrication (FFF) 3D printing technique. The uses of both short and continuous fibre-reinforced polymer composites are reviewed. Finally, examples of some applications of FFF printed polymer composites using robotic processes are highlighted.
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Gao, Xin Rui. „3D Animation Technologies and Efficiency“. Applied Mechanics and Materials 421 (September 2013): 681–84. http://dx.doi.org/10.4028/www.scientific.net/amm.421.681.
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3D animation technologies include FFD, Hierarchies and Kinematics (FK and IK), Dynamic animation, Keyframe, Time based animation, Non-linear animation, Path animation, Layered animation, and Motion capture animation etc. They are related with the efficiency of 3D animation. This thesis discusses these technologies separately and suggests methods to enhance the efficiency of 3D animation.
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Stano, Gianni, Luca Arleo und Gianluca Percoco. „Additive Manufacturing for Soft Robotics: Design and Fabrication of Airtight, Monolithic Bending PneuNets with Embedded Air Connectors“. Micromachines 11, Nr. 5 (09.05.2020): 485. http://dx.doi.org/10.3390/mi11050485.
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Air tightness is a challenging task for 3D-printed components, especially for fused filament fabrication (FFF), due to inherent issues, related to the layer-by-layer fabrication method. On the other hand, the capability of 3D print airtight cavities with complex shapes is very attractive for several emerging research fields, such as soft robotics. The present paper proposes a repeatable methodology to 3D print airtight soft actuators with embedded air connectors. The FFF process has been optimized to manufacture monolithic bending PneuNets (MBPs), an emerging class of soft robots. FFF has several advantages in soft robot fabrication: (i) it is a fully automated process which does not require manual tasks as for molding, (ii) it is one of the most ubiquitous and inexpensive (FFF 3D printers costs < $200) 3D-printing technologies, and (iii) more materials can be used in the same printing cycle which allows embedding of several elements in the soft robot body. Using commercial soft filaments and a dual-extruder 3D printer, at first, a novel air connector which can be easily embedded in each soft robot, made via FFF technology with a single printing cycle, has been fabricated and tested. This new embedded air connector (EAC) prevents air leaks at the interface between pneumatic pipe and soft robot and replaces the commercial air connections, often origin of leakages in soft robots. A subsequent experimental study using four different shapes of MBPs, each equipped with EAC, showed the way in which different design configurations can affect bending performance. By focusing on the best performing shape, among the tested ones, the authors studied the relationship between bending performance and air tightness, proving how the Design for Additive Manufacturing approach is essential for advanced applications involving FFF. In particular, the relationship between chamber wall thickness and printing parameters has been analyzed, the thickness of the walls has been studied from 1.6 to 1 mm while maintaining air tightness and improving the bending angle by 76.7% under a pressure of 4 bar. It emerged that the main printing parameter affecting chamber wall air tightness is the line width that, in conjunction with the wall thickness, can ensure air tightness of the soft actuator body.
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García-Hernández, Trinitat, Aurora Vicedo-González, Beatriz Sánchez-Nieto, Maite Romero-Expósito und Joan Roselló-Ferrando. „PERIPHERAL SURFACE DOSE FROM A LINEAR ACCELERATOR: RADIOCHROMIC FILM EXPERIMENTAL MEASUREMENTS OF FLATTENING FILTER FREE VERSUS FLATTENED BEAMS“. Radiation Protection Dosimetry 188, Nr. 3 (10.01.2020): 285–98. http://dx.doi.org/10.1093/rpd/ncz286.
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Abstract There is a growing interest in the use of flattening filter free (FFF) beams due to the shorter treatment times. The reduction of head scatter suggests a better radiation protection to radiotherapy patients, considering the expected decrease in peripheral surface dose (PSD). In this work, PSD of flattened (FF) and FFF-photon beams was compared. A radiochromic film calibration method to reduce energy dependence was used. PSD was measured at distances from 2 to 50 cm to the field border for different square field sizes, modifying relevant clinical parameters. Also, clinical breast and prostate stereotactic body radiotherapy (SBRT) plans were studied. For square beams, FFF PSD is lower compared with FF PSD (differences ranging from 3 to 64%) and 10 MV FFF yields to the lowest value, for distances greater than 5 cm. For SBRT plans, near and far away from the field border, there is a reduction of PSD for FFF-beams, but the behavior at intermediate distances should be checked depending on the case.
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Ong U Jing, Daniel, Declan Devine und John Lyons. „3D Printed End of Arm Tooling (EOAT) for Robotic Automation“. Robotics 7, Nr. 3 (05.09.2018): 49. http://dx.doi.org/10.3390/robotics7030049.
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This research furthers the practice of designing and manufacturing End of Arm Tooling (EOAT) by utilizing a low cost additive manufacturing Fused Filament Fabrication (FFF) technique to enable tool weight saving and provision of low cost EOATs on demand, thereby facilitating zero inventory lean manufacturing. The materials used in this research for the fabrication of the EOAT parts were Acrylonitrile butadiene styrene (ABS) and nylon with infill densities of 20% and 100%. Three-point flexural tests were performed to determine the differences in strength and stiffness between varying polymers, infill ratios, and a standard metal part. Additionally, potential weight savings were identified and challenges with utilizing low cost FFF technologies are outlined. A motion of programmed trajectories was executed utilizing a standard 6-axis robot and the power consumption was evaluated. This study demonstrates the utility of using thermoplastic material with the fabrication of 3D printed parts used in EOATs.
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Bonada, Jordi, Mª Magdalena Pastor und Irene Buj-Corral. „Influence of Infill Pattern on the Elastic Mechanical Properties of Fused Filament Fabrication (FFF) Parts through Experimental Tests and Numerical Analyses“. Materials 14, Nr. 18 (21.09.2021): 5459. http://dx.doi.org/10.3390/ma14185459.
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Fused Filament Fabrication (FFF) is one of the most extensive additive manufacturing technologies for printing prototypes or final parts in various fields. Some printed parts need to meet structural requirements to be functional parts. Therefore, it is necessary to know the mechanical behavior of the printed samples as a function of the printing parameters in order to optimize the material used during the manufacturing process. It is known that FFF parts can present orthotropic characteristics as a consequence of the manufacturing process, in which the material is deposited layer by layer. Therefore, these characteristics must be considered for a correct evaluation of the printed parts from a structural point of view. In this paper, the influence of the type of filling pattern on the main mechanical properties of the printed parts is analyzed. For this purpose, the first parts are 3D printed using three different infill patterns, namely grid, linear with a raster orientation of 0 and 90°, and linear with a raster orientation of 45°. Then, experimental tensile tests, on the one hand, and numerical analyses using finite elements, on the other hand, are carried out. The elastic constants of the material are obtained from the experimental tests. From the finite element analysis, using a simple approach to create a Representative Volume Model (RVE), the constitutive characteristics of the material are estimated: Young’s Moduli and Poisson’s ratios of the printed FFF parts. These values are successfully compared with those of the experimental tests. The results clearly show differences in the mechanical properties of the FFF printed parts, depending on the internal arrangement of the infill pattern, even if similar 3D printing parameters are used.
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Koprnicky, Jan, Jiří Šafka und Michal Ackermann. „Using of 3D Printing Technology in Low Cost Prosthetics“. Materials Science Forum 919 (April 2018): 199–206. http://dx.doi.org/10.4028/www.scientific.net/msf.919.199.
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The 3D printing technology used for final production of upper limb prostheses is the topicof this article. It focuses on different 3D printing technologies and testing of different thermoplasticmaterials. As the testing object an index finger of HACKberry open source myoelectric bionic handwas used. This part was 3D printed by using of different printing technologies (FFF/FDM, SLA, SLS,PolyJet), and different materials (PLA, ABS, PC-ABS, Though, etc.), and different strategies (heightof layers). The fingers were mechanically tested to simulate flexion in a tip pinch grip. At the endof this paper results of this research and testing is summarized, and optimal material, technology andstrategies of parts production is highlighted.
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Zeraatkar, Filippini und Percoco. „On the Impact of the Fabrication Method on the Performance of 3D Printed Mixers“. Micromachines 10, Nr. 5 (30.04.2019): 298. http://dx.doi.org/10.3390/mi10050298.
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A wide variety of 3D printing technologies have been used for the fabrication of lab-on-a-chip (LOC) devices in recent years. Despite the large number of studies having examined the use of 3D printing technologies in microfluidic devices, the effect of the fabrication method on their performance has received little attention. In this paper, a comparison is shown between unibody-LOC micro-mixers, a particular type of monolithic design for 3D printed LOCs, fabricated in polyjet, stereolithography (SLA) and fused deposition modelling (FDM or FFF) platforms, paying particular attention to the inherent limitations of each fabrication platform and how these affect the performance of the manufactured devices.
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Korotchenko, A. Yu, D. E. Khilkov, M. V. Tverskoy und A. A. Khilkova. „Research of 3D Printing Modes of Feedstock for Metal Injection Molding“. Materials Science Forum 992 (Mai 2020): 461–66. http://dx.doi.org/10.4028/www.scientific.net/msf.992.461.
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In this work, to reduce the cost of production of parts using injection molding metal technology (MIM technology), it is proposed to use additive technologies (AT) for the manufacture of green parts. The use of AT allows us to abandon expensive molds and expand the field of use of the MIM of technology in single and small-scale production. For manufacture of green parts, the technology of manufacturing fused filament (Fused Filament Fabrication – FFF) is offered. The original composition of the metal powder mix (feedstock) and the filament manufacturing modes for 3D printing have been developed for the FFF technology. The cost of filament is much lower than its analogs. The factors affecting the print quality of green part are considered. All factors are divided into two groups depending on the possibility of their change during printing. The research of the influence of the coefficient filament supply on the geometry of green parts during 3D printing is presented.
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Walker, Jenna Stephanie, John Arnold, Cynthiya Shrestha und Damon Smith. „Antibacterial silver submicron wire-polylactic acid composites for fused filament fabrication“. Rapid Prototyping Journal 26, Nr. 1 (06.01.2020): 32–38. http://dx.doi.org/10.1108/rpj-04-2019-0100.
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Purpose The purpose of this study is to explore the use of silver submicron-scale wire (AgSMW) additives in filament feedstock for fused filament fabrication (FFF) additive manufacturing technologies. The antibacterial effect of the additive on printed objects is assessed and its impact on mechanical behavior is determined. Design/methodology/approach AgSMW-PLA composite FFF filaments were fabricated by solution processing, granulation and extrusion. The reduction in the growth of Escherichia coli (E. coli) is measured after exposure to FFF-printed composite test specimens with AgSMW additive concentrations ranging from 0.0 to 10.0 weight per cent. The effect of the additive addition on the thermal properties and tensile mechanical performance was measured. Scanning electron microscopy (SEM) was used to analyze the composite microstructure and fracture behavior. Findings E. coli growth was reduced by approximately 50 per cent at the highest additive concentration of 10.0 weight per cent. This is attributed to the release of silver ions through water diffusion into the bulk of the composite. The ultimate tensile strength declined with increasing AgSMW concentration with a moderate reduction of 18 per cent at 10.0 weight per cent. The elastic modulus did not vary significantly at any of the concentrations studied. The ductility of the composite was only notably reduced at the highest concentration. The reduction in mechanical strength and strain at break is attributed to an increase in void defects in the composite with increasing additive concentration. Originality/value This study demonstrates the successful incorporation of AgSMWs into FFF-compatible filaments for use in commercially available printing systems. The results demonstrate significant reduction of bacteria growth when using these materials. While the mechanical performance degrades slightly, the results indicate the material’s efficacy for a variety of potential biomedical applications. As a proof of concept, surgical tools were printed using the composite.
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Mikulová, Magda. „Content of free fatty acids, lipolytic bacteria and somatic cells in relation to milking technology“. Journal of Agrobiology 28, Nr. 1 (01.08.2011): 49–54. http://dx.doi.org/10.2478/v10146-011-0005-8.
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Content of free fatty acids, lipolytic bacteria and somatic cells in relation to milking technologyThe contents of free fatty acids (FFA) and counts of total bacteria, psychrotrophic lipolytic bacteria (PLiBC) and somatic cells were determined in 150 samples of cow's bulk raw milk on 20 farms with three different milking technologies in South Bohemia during 2008-10. FFA were determined using an extraction-titration method. Within the compared technologies, the highest mean values of FFA (3.88 mmol 100 g-1; P<0.001) and PLiBC (696 CFU ml-1) were observed on farms with pipeline milking in stalls. The lowest mean FFA level (1.54 mmol 100 g-1) was determined on farms with an automatic milking system. Medium values were determined on farms with parlour milking.
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Lüchtenborg, Jörg, Felix Burkhardt, Julian Nold, Severin Rothlauf, Christian Wesemann, Stefano Pieralli, Gregor Wemken, Siegbert Witkowski und Benedikt C. Spies. „Implementation of Fused Filament Fabrication in Dentistry“. Applied Sciences 11, Nr. 14 (13.07.2021): 6444. http://dx.doi.org/10.3390/app11146444.
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Additive manufacturing is becoming an increasingly important technique for the production of dental restorations and assistive devices. The most commonly used systems are based on vat polymerization, e.g., stereolithography (SLA) and digital light processing (DLP). In contrast, fused filament fabrication (FFF), also known under the brand name fused deposition modeling (FDM), is rarely applied in the dental field. This might be due to the reduced accuracy and resolution of FFF compared to vat polymerization. However, the use of FFF in the dental sector seems very promising for in-house production since it presents a cost-effective and straight forward method. The manufacturing of nearly ready-to-use parts with only minimal post-processing can be considered highly advantageous. Therefore, the objective was to implement FFF in a digital dental workflow. The present report demonstrates the production of surgical guides for implant insertion by FFF. Furthermore, a novel approach using a temperature-sensitive filament for bite registration plates holds great promise for a simplified workflow. In combination with a medical-grade filament, a multi-material impression tray was printed for optimized impression taking of edentulous patients. Compared to the conventional way, the printed thermoplastic material is pleasant to model and can allow clean and fast work on the patient.
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Rendeki, Szilard, Balint Nagy, Matyas Bene, Attila Pentek, Luca Toth, Zalan Szanto, Roland Told und Peter Maroti. „An Overview on Personal Protective Equipment (PPE) Fabricated with Additive Manufacturing Technologies in the Era of COVID-19 Pandemic“. Polymers 12, Nr. 11 (16.11.2020): 2703. http://dx.doi.org/10.3390/polym12112703.
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Different additive manufacturing technologies have proven effective and useful in remote medicine and emergency or disaster situations. The coronavirus disease 2019 (COVID-19) disease, caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) virus, has had a huge impact on our society, including in relation to the continuous supply of personal protective equipment (PPE). The aim of the study is to give a detailed overview of 3D-printed PPE devices and provide practical information regarding the manufacturing and further design process, as well as describing the potential risks of using them. Open-source models of a half-face mask, safety goggles, and a face-protecting shield are evaluated, considering production time, material usage, and cost. Estimations have been performed with fused filament fabrication (FFF) and selective laser sintering (SLS) technology, highlighting the material characteristics of polylactic acid (PLA), polyamide, and a two-compound silicone. Spectrophotometry measurements of transparent PMMA samples were performed to determine their functionality as goggles or face mask parts. All the tests were carried out before and after the tetra-acetyl-ethylene-diamine (TAED)-based disinfection process. The results show that the disinfection has no significant effect on the mechanical and structural stability of the used polymers; therefore, 3D-printed PPE is reusable. For each device, recommendations and possible means of development are explained. The files of the modified models are provided. SLS and FFF additive manufacturing technology can be useful tools in PPE development and small-series production, but open-source models must be used with special care.
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DOROKHOV, ALEKSEI S., und ALEKSEI S. SVIRIDOV. „APPLICATION OF ADDITIVE TECHNOLOGIES IN THE TECHNICAL SERVICE OF GARDEN EQUIPMENT“. AGRICULTURAL ENGINEERING, Nr. 6 (2020): 39–44. http://dx.doi.org/10.26897/2687-1149-2020-6-39-44.
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The paper considers the analysis of the market for garden equipment. The authors consider some information on garden equipment failures, using an example of Husqvarna trimmers. They also assess a possibility of using additive technologies to manufacture sliding bearings for mechanical drives of garden equipment. For testing the physical and mechanical properties, a batch of samples was prepared by means of 3D printing using FDM (FFF) technology. According to the ASTM D638-14 standard, samples were prepared on a PICASO 3D Desingner X Pro 3D printer. Samples were made of ABS-plastic and PA12 with diff erent degrees of fi lling: 20, 50 and 100%. It is noted that the destruction pattern of samples made of diff erent materials is signifi cantly diff erent. Samples made from ABS plastics are more fragile than samples made from PA12. According to the test results, PA12 with 100% fi lling have shown the best results, which makes them suitable for use in the manufacture of slide bearings by means of 3D printing.
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Costa, José, Elsa Sequeiros, Maria Teresa Vieira und Manuel Vieira. „Additive Manufacturing“. U.Porto Journal of Engineering 7, Nr. 3 (30.04.2021): 53–69. http://dx.doi.org/10.24840/2183-6493_007.003_0005.
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Additive manufacturing (AM) is one of the most trending technologies nowadays, and it has the potential to become one of the most disruptive technologies for manufacturing. Academia and industry pay attention to AM because it enables a wide range of new possibilities for design freedom, complex parts production, components, mass personalization, and process improvement. The material extrusion (ME) AM technology for metallic materials is becoming relevant and equivalent to other AM techniques, like laser powder bed fusion. Although ME cannot overpass some limitations, compared with other AM technologies, it enables smaller overall costs and initial investment, more straightforward equipment parametrization, and production flexibility.This study aims to evaluate components produced by ME, or Fused Filament Fabrication (FFF), with different materials: Inconel 625, H13 SAE, and 17-4PH. The microstructure and mechanical characteristics of manufactured parts were evaluated, confirming the process effectiveness and revealing that this is an alternative for metal-based AM.
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Yasa, Evren, und Kıvılcım Ersoy. „Dimensional Accuracy and Mechanical Properties of Chopped Carbon Reinforced Polymers Produced by Material Extrusion Additive Manufacturing“. Materials 12, Nr. 23 (25.11.2019): 3885. http://dx.doi.org/10.3390/ma12233885.
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Fused Filament Fabrication (FFF), classified under material extrusion additive manufacturing technologies, is a widely used method for fabricating thermoplastic parts with high geometrical complexity. To improve the mechanical properties of pure thermoplastic materials, the polymeric matrix may be reinforced by different materials such as carbon fibers. FFF is an advantageous process for producing polymer matrix composites because of its low cost of investment, high speed and simplicity as well as the possibility to use multiple nozzles with different materials. In this study, the aim was to investigate the dimensional accuracy and mechanical properties of chopped carbon-fiber-reinforced tough nylon produced by the FFF process. The dimensional accuracy and manufacturability limits of the process are evaluated using benchmark geometries as well as process-inherent effects like stair-stepping effect. The hardness and tensile properties of produced specimens in comparison to tough nylon without any reinforcement, as well as continuous carbon-reinforced specimens, were presented by taking different build directions and various infill ratios. The fracture surfaces of tensile specimens were observed using a Scanning Electron Microscope (SEM). The test results showed that there was a severe level of anisotropy in the mechanical properties, especially the modulus of elasticity, due to the insufficient fusion between deposited layers in the build direction. Moreover, continuous carbon-reinforced specimens exhibited very high levels of tensile strength and modulus of elasticity whereas the highest elongation was achieved by tough nylon without reinforcement. The failure mechanisms were found to be inter-layer porosity between successive tracks, as well as fiber pull out.
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Chacón, Jesús Miguel, Miguel Ángel Caminero, Pedro José Núñez, Eustaquio García-Plaza und Jean Paul Bécar. „Effect of nozzle diameter on mechanical and geometric performance of 3D printed carbon fibre-reinforced composites manufactured by fused filament fabrication“. Rapid Prototyping Journal 27, Nr. 4 (17.05.2021): 769–84. http://dx.doi.org/10.1108/rpj-10-2020-0250.
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Purpose Fused filament fabrication (FFF) is one of the most popular additive manufacturing (AM) technologies due to its ability to build thermoplastic parts with complex geometries at low cost. The FFF technique has been mainly used for rapid prototyping owing to the poor mechanical and geometrical properties of pure thermoplastic parts. However, both the development of new fibre-reinforced filaments with improved mechanical properties, and more accurate composite 3D printers have broadened the scope of FFF applications to functional components. FFF is a complex process with a large number of parameters influencing product quality and mechanical properties, and the effects of the combined parameters are usually difficult to evaluate. An array of parameter combinations has been analysed for improving the mechanical performance of thermoplastic parts such as layer thickness, build orientation, raster angle, raster width, air gap, infill density and pattern, fibre volume fraction, fibre layer location, fibre orientation and feed rate. This study aims to assess the effects of nozzle diameter on the mechanical performance and the geometric properties of 3D printed short carbon fibre-reinforced composites processed by the FFF technique. Design methodology approach Tensile and three-point bending tests were performed to characterise the mechanical response of the 3D printed composite samples. The dimensional accuracy, the flatness error and surface roughness of the printed specimens were also evaluated. Moreover, manufacturing costs, which are related to printing time, were evaluated. Finally, scanning electron microscopy images of the printed samples were analysed to estimate the porosity as a function of the nozzle diameter and to justify the effect of nozzle diameter on dimensional accuracy and surface roughness. Findings The effect of nozzle diameter on the mechanical and geometric quality of 3D printed composite samples was significant. In addition, large nozzle diameters tended to increase mechanical performance and enhance surface roughness, with a reduction in manufacturing costs. In contrast, 3D printed composite samples with small nozzle diameter exhibited higher geometric accuracy. However, the effect of nozzle diameter on the flatness error and surface roughness was of slight significance. Finally, some print guidelines are included. Originality value The effect of nozzle diameter, which is directly related to product quality and manufacturing costs, has not been extensively studied. The presented study provides more information regarding the dependence of the mechanical, microstructural and geometric properties of short carbon fibre-reinforced nylon composite components on nozzle diameter.
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Msallem, Bilal, Neha Sharma, Shuaishuai Cao, Florian S. Halbeisen, Hans-Florian Zeilhofer und Florian M. Thieringer. „Evaluation of the Dimensional Accuracy of 3D-Printed Anatomical Mandibular Models Using FFF, SLA, SLS, MJ, and BJ Printing Technology“. Journal of Clinical Medicine 9, Nr. 3 (17.03.2020): 817. http://dx.doi.org/10.3390/jcm9030817.
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With the rapid progression of additive manufacturing and the emergence of new 3D printing technologies, accuracy assessment is mostly being performed on isosymmetric-shaped test bodies. However, the accuracy of anatomic models can vary. The dimensional accuracy of root mean square values in terms of trueness and precision of 50 mandibular replicas, printed with five common printing technologies, were evaluated. The highest trueness was found for the selective laser sintering printer (0.11 ± 0.016 mm), followed by a binder jetting printer (0.14 ± 0.02 mm), and a fused filament fabrication printer (0.16 ± 0.009 mm). However, highest precision was identified for the fused filament fabrication printer (0.05 ± 0.005 mm) whereas other printers had marginally lower values. Despite the statistically significance (p < 0.001), these differences can be considered clinically insignificant. These findings demonstrate that all 3D printing technologies create models with satisfactory dimensional accuracy for surgical use. Since satisfactory results in terms of accuracy can be reached with most technologies, the choice should be more strongly based on the printing materials, the intended use, and the overall budget. The simplest printing technology (fused filament fabrication) always scored high and thus is a reliable choice for most purposes.
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Oehlmann, Paul, Paul Osswald, Juan Camilo Blanco, Martin Friedrich, Dominik Rietzel und Gerd Witt. „Modeling Fused Filament Fabrication using Artificial Neural Networks“. Production Engineering 15, Nr. 3-4 (07.02.2021): 467–78. http://dx.doi.org/10.1007/s11740-021-01020-y.
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AbstractWith industries pushing towards digitalized production, adaption to expectations and increasing requirements for modern applications, has brought additive manufacturing (AM) to the forefront of Industry 4.0. In fact, AM is a main accelerator for digital production with its possibilities in structural design, such as topology optimization, production flexibility, customization, product development, to name a few. Fused Filament Fabrication (FFF) is a widespread and practical tool for rapid prototyping that also demonstrates the importance of AM technologies through its accessibility to the general public by creating cost effective desktop solutions. An increasing integration of systems in an intelligent production environment also enables the generation of large-scale data to be used for process monitoring and process control. Deep learning as a form of artificial intelligence (AI) and more specifically, a method of machine learning (ML) is ideal for handling big data. This study uses a trained artificial neural network (ANN) model as a digital shadow to predict the force within the nozzle of an FFF printer using filament speed and nozzle temperatures as input data. After the ANN model was tested using data from a theoretical model it was implemented to predict the behavior using real-time printer data. For this purpose, an FFF printer was equipped with sensors that collect real time printer data during the printing process. The ANN model reflected the kinematics of melting and flow predicted by models currently available for various speeds of printing. The model allows for a deeper understanding of the influencing process parameters which ultimately results in the determination of the optimum combination of process speed and print quality.
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Xiao, Xinyi, Byeong-Min Roh und Feng Zhu. „Strength Enhancement in Fused Filament Fabrication via the Isotropy Toolpath“. Applied Sciences 11, Nr. 13 (30.06.2021): 6100. http://dx.doi.org/10.3390/app11136100.
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The fused filament fabrication (FFF) process deposits thermoplastic material in a layer-by-layer manner, expanding the design space and manufacturing capability compared with traditional manufacturing. However, the FFF process is inherently directional as the material is deposited in a layer-wise manner. Therefore, the in-plane material cannot reach the isotropy character when performing the tensile test. This would cause the strength of the print components to vary based on the different process planning selections (building orientation, toolpath pattern). The existing toolpaths, primarily used in the FFF process, are linear, zigzag, and contour toolpaths, which always accumulate long filaments and are unidirectional. Thus, this would create difficulties in improving the mechanical strength from the existing toolpath strategies due to the material in-plane anisotropy. In this paper, an in-plane isotropy toolpath pattern is generated to enhance the mechanical strength in the FFF process. The in-plane isotropy can be achieved through continuous deposition while maintaining randomized distribution within a layer. By analyzing the tensile strength on the specimens made by traditional in-plane anisotropy toolpath and the proposed in-plane isotropy toolpath, our results suggest that the mechanical strength can be reinforced by at least 20% using our proposed toolpath strategy in extrusion-based additive manufacturing.
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Mizera, Ales, Martin Bednarik, Martin Mizera, Katarina Tomanova und Martin Mohorko. „Tensile impact behaviour of 3D printed parts on FFF/FDM printer Zortrax M200“. MATEC Web of Conferences 210 (2018): 04049. http://dx.doi.org/10.1051/matecconf/201821004049.
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To obtain the deeper knowledge about the mechanical behaviour of 3D printed polymeric materials it is necessary to study the material properties from the beginning to the end. The commonly processed polymeric materials (via injection moulding etc.) are already deeply studied and evaluated, but 3D printed specimens in the various orientation build are not yet. In this study the tensile impact test specimens were fabricated via a desktop material extrusion 3D printer Zortrax M200 processing ABS and HIPS in build orientation XY. The 3D printed tensile impact test specimens were examined to compare the effect of layer thickness. Impact pendulum Zwick HIT50P was used for tensile impact tests according to ISO 8256 standard. Optical microscopy was utilized to perform fractography on impact test specimens to explore the effect of the layer thickness on the fracture surface morphology of the failed specimens. This study demonstrates the need for material testing for specific processing as additive manufacturing technologies.
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Poole, R., V. McCracken, M. Rhoads und K. Lee. „213 MATURATION OF OOCYTES WITH FOLLICULAR FLUID FROM GILTS CONSUMING HIGH FAT AND FRUCTOSE AFFECTS SUBSEQUENT EMBRYO DEVELOPMENT“. Reproduction, Fertility and Development 28, Nr. 2 (2016): 237. http://dx.doi.org/10.1071/rdv28n2ab213.
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Infertility among women has become a growing issue in the world requiring a significant number to seek treatment by means of assisted reproductive technologies. One suggested reason for the fertility issue, which is known to specifically affect oocyte quality, is the modern diet. Previously, we have demonstrated that feeding a high-fructose diet to gilts led to poor reproductive tract characteristics and infertility. In this study, pre-pubescent gilts were fed either a high-fructose; high-fat diet (HFHF), with 15% beef tallow and 35% fructose; or an industry control diet (IND). Porcine follicular fluid (pFF) collected from these gilts was introduced into in vitro maturation systems to determine whether characteristics of the follicular fluid affect oocyte competence and embryo development. Follicles from ovaries, collected at a local abattoir, were aspirated by an 18 G needle attached to a 10-mL sterile syringe. Then selected cumulus‐oocyte complexes were maturated in vitro in a TCM-199 maturation media with cysteine, glucose, sodium pyruvate, epidermal growth factor (EGF), FSH, LH, and 20% pFF from treatment groups. Additionally, another group of oocytes, labelled follicle fluid free (FFF), were maturated in TCM-199 media without pFF. Three replicate experiments were conducted using a total of 365 oocytes, 124 FFF, 121 IND, and 120 HFHF. Oocytes were denuded by exposure to 0.1% hyaluronidase and oocytes that reached metaphase II (MII) were selected for in vitro fertilisation. After 5 h of co-incubation in modified Tween medium B with milk powder (mTBM)-based IVF media, presumable zygotes were transferred to porcine zygote medium-3 (PZM-3). Blastocyst frequency was recorded on Days 5 and 6. Day 6 blastocysts were stained with Hoechst for total cell number evaluation. The frequencies of blastocyst formation among the treatment groups were compared by a chi-squared test, and total cell numbers were compared by Student's t-test. Statistical significance was defined by P < 0.05. The frequency of oocytes reaching metaphase II (MII) were observed as 77.4% FFF, 72.7% IND, and 71.7% HFHF (P > 0.05), indicating the supplementation of pFF did not affect maturation. Day 5 blastocysts were observed at frequencies of 8.3% FFF, 6.8% IND, and 4.7% HFHF and did not differ. However, frequency of Day 6 blastocysts from HFHF group was tended to be lower compared with that of other groups; 12.5% FFF, 11.4% IND, and 4.7% HFHF (P = 0.06 and P = 0.1). Average total cell number of Day 6 blastocysts observed were 41.0 ± 9.1 FFF, 36.0 ± 8.9 IND, and 48.3 ± 10.6 HFHF. The total cell number from HFHF group tended to be higher than only that of IND group (P = 0.07). Based on these results, we concluded that the follicular fluid of females consuming HFHF diets did not have impact on nuclear maturation of oocytes but might affect oocyte competency, thus resulting in detrimental effects on subsequent development of embryos, especially blastocyst formation. Further studies will help us identify more specific effects of nutrition on oogenesis and subsequent embryo development.
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Sztorch, Bogna, Dariusz Brząkalski, Marek Jałbrzykowski und Robert E. Przekop. „Processing Technologies for Crisis Response on the Example of COVID-19 Pandemic—Injection Molding and FFF Case Study“. Processes 9, Nr. 5 (30.04.2021): 791. http://dx.doi.org/10.3390/pr9050791.
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The paper presents a comparison of two methods of manufacturing utility objects made of plastics, applied to the emerging immediate need in the field of quick provision of personal protective equipment for medical services. The traditional processing method, which is injection molding (IM), and a modern rapid prototyping method, which is fused filament fabrication (FFF) 3D printing, were compared in terms of unit costs and production possibilities at various timeframes. The paper presents the effects of launching two production processes of protective helmets (face shields) using the example of real cases implemented ad hoc during the epidemic development. The implementation of the protective helmet production project based on polyamide-6 processing showed the real possibilities of quickly launching the rapid production of protective equipment with the aid of mold injection technology.
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Tosto, Claudio, Jacopo Tirillò, Fabrizio Sarasini und Gianluca Cicala. „Hybrid Metal/Polymer Filaments for Fused Filament Fabrication (FFF) to Print Metal Parts“. Applied Sciences 11, Nr. 4 (05.02.2021): 1444. http://dx.doi.org/10.3390/app11041444.
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The exploitation of mechanical properties and customization possibilities of 3D printed metal parts usually come at the cost of complex and expensive equipment. To address this issue, hybrid metal/polymer composite filaments have been studied allowing the printing of metal parts by using the standard Fused Filament Fabrication (FFF) approach. The resulting hybrid metal/polymer part, the so called “green”, can then be transformed into a dense metal part using debinding and sintering cycles. In this work, we investigated the manufacturing and characterization of green and sintered parts obtained by FFF of two commercial hybrid metal/polymer filaments, i.e., the Ultrafuse 316L by BASF and the 17-4 PH by Markforged. The Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectrometry (EDS) analyses of the mesostructure highlighted incomplete raster bonding and voids like those observed in conventional FFF-printed polymeric structures despite the sintering cycle. A significant role in the tensile properties was played by the building orientation, with samples printed flatwise featuring the highest mechanical properties, though lower than those achievable with standard metal additive manufacturing techniques.
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Gewelber, O., Y. Rosenthal, D. Ashkenazi und A. Stern. „Mechanical Properties, Structure and Fracture Behavior of Additive Manufactured FFF-ABS Specimens“. Annals of Dunarea de Jos University of Galati Fascicle XII Welding Equipment and Technology 31 (28.12.2020): 71–78. http://dx.doi.org/10.35219/awet.2020.11.
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The Fused Filament Fabrication (FFF) method is one of the most important additive manufacturing (AM) technologies. This technology is used today with various kinds of thermoplastic materials, including ABS. The present study deals with the flexural strength and axial deflection of ABS specimens versus relative density, to observe the influence of build-orientations, build model and microscopic level defects of these properties. In this study, the mechanical and structural characterization of AM-FFF ABS material was studied by CAD modelling of different orientations, three point bending mechanical testing, visual testing, and multifocal light microscopy observation, including fractography analysis. To that end, three different standard building orientations (Flat, On Edge and Upright) were printed, and each was built in two different angle orientations (-45o/+45o and 0°/90o). Based on the three point bending testing results, it was found that the specimen with the highest flexural strength was not necessarily the one with the highest deflection. It was also observed that On Edge 0/+90o orientations showed a relatively larger flexural strength difference in comparison to other building orientations (Flat and Upright). When the mechanical properties achieved from a bending test next to the building platform were compared to the properties far from the building platform, only a slight difference was found, which means that the flexural strength difference results from the building strategy and it is not related to the specific bending surface. Based on fractography observation, there is a major difference in the mechanical properties and fracture surface appearance, when the samples are bent between the layers (Upright orientation) or when the samples are bent through the layers (Flat and On Edge orientation).
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Cardona, Carolina, Abigail H. Curdes und Aaron J. Isaacs. „Effects of Filament Diameter Tolerances in Fused Filament Fabrication“. IU Journal of Undergraduate Research 2, Nr. 1 (31.05.2016): 44–47. http://dx.doi.org/10.14434/iujur.v2i1.20917.
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Fused filament fabrication (FFF) is one of the most popular additive manufacturing (3D printing) technologies due to the growing availability of low-cost desktop 3D printers and the relatively low cost of the thermoplastic filament used in the 3D printing process. Commercial filament suppliers, 3D printer manufacturers, and end-users regard filament diameter tolerance as an important indicator of the 3D printing quality. Irregular filament diameter affects the flow rate during the filament extrusion, which causes poor surface quality, extruder jams, irregular gaps in-between individual extrusions, and/or excessive overlap, which eventually results in failed 3D prints. Despite the important role of the diameter consistency in the FFF process, few studies have addressed the required tolerance level to achieve highest 3D printing quality. The objective of this work is to develop the testing methods to measure the filament tolerance and control the filament fabrication process. A pellet-based extruder is utilized to fabricate acrylonitrile butadiene styrene (ABS) filament using a nozzle of 1.75 mm in diameter. Temperature and extrusion rate are controlled parameters. An optical comparator and an array of digital calipers are used to measure the filament diameter. The results demonstrate that it is possible to achieve high diameter consistency and low tolerances (0.01mm) at low extrusion temperature (180 °C) and low extrusion rate (10 in/min).
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Buj-Corral, Irene, Aitor Tejo-Otero und Felip Fenollosa-Artés. „Development of AM Technologies for Metals in the Sector of Medical Implants“. Metals 10, Nr. 5 (23.05.2020): 686. http://dx.doi.org/10.3390/met10050686.
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Additive manufacturing (AM) processes have undergone significant progress in recent years, having been implemented in sectors as diverse as automotive, aerospace, electrical component manufacturing, etc. In the medical sector, different devices are printed, such as implants, surgical guides, scaffolds, tissue engineering, etc. Although nowadays some implants are made of plastics or ceramics, metals have been traditionally employed in their manufacture. However, metallic implants obtained by traditional methods such as machining have the drawbacks that they are manufactured in standard sizes, and that it is difficult to obtain porous structures that favor fixation of the prostheses by means of osseointegration. The present paper presents an overview of the use of AM technologies to manufacture metallic implants. First, the different technologies used for metals are presented, focusing on the main advantages and drawbacks of each one of them. Considered technologies are binder jetting (BJ), selective laser melting (SLM), electron beam melting (EBM), direct energy deposition (DED), and material extrusion by fused filament fabrication (FFF) with metal filled polymers. Then, different metals used in the medical sector are listed, and their properties are summarized, with the focus on Ti and CoCr alloys. They are divided into two groups, namely ferrous and non-ferrous alloys. Finally, the state-of-art about the manufacture of metallic implants with AM technologies is summarized. The present paper will help to explain the latest progress in the application of AM processes to the manufacture of implants.
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Pranzo, Daniela, Piero Larizza, Daniel Filippini und Gianluca Percoco. „Extrusion-Based 3D Printing of Microfluidic Devices for Chemical and Biomedical Applications: A Topical Review“. Micromachines 9, Nr. 8 (27.07.2018): 374. http://dx.doi.org/10.3390/mi9080374.
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One of the most widespread additive manufacturing (AM) technologies is fused deposition modelling (FDM), also known as fused filament fabrication (FFF) or extrusion-based AM. The main reasons for its success are low costs, very simple machine structure, and a wide variety of available materials. However, one of the main limitations of the process is its accuracy and finishing. In spite of this, FDM is finding more and more applications, including in the world of micro-components. In this world, one of the most interesting topics is represented by microfluidic reactors for chemical and biomedical applications. The present review focusses on this research topic from a process point of view, describing at first the platforms and materials and then deepening the most relevant applications.
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Radkhah, Ali Reza, und Soheil Eagderi. „Fish Protection Technologies and Fish Ways for Downstream MigrationU.Schwevers & B.Adam, Springer, Switzerland, 2020. ISBN: 9783030192426“. Fish and Fisheries 21, Nr. 6 (07.09.2020): 1277–78. http://dx.doi.org/10.1111/faf.12492.
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Kladovasilakis, Nikolaos, Paschalis Charalampous, Konstantinos Tsongas, Ioannis Kostavelis, Dimitrios Tzetzis und Dimitrios Tzovaras. „Experimental and Computational Investigation of Lattice Sandwich Structures Constructed by Additive Manufacturing Technologies“. Journal of Manufacturing and Materials Processing 5, Nr. 3 (31.08.2021): 95. http://dx.doi.org/10.3390/jmmp5030095.
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Additive Manufacturing (AM) technologies offer the ability to construct complex geometrical structures in short manufacturing lead time coupled with a relatively low production cost when compared to traditional manufacturing processes. The next trend in mechanical engineering design is the adaption of design strategies that build products with lightweight lattice geometries like sandwich structures. These structures possess low mass, large surface area to volume ratio, high porosity, and adequate mechanical behavior, which are properties of great importance in scientific fields such as bioengineering, automotive, and aerospace engineering. The present work is focused on producing sandwich structures with complex lattice patterns like the Triply Periodic Minimal Surface (TPMS) Schwarz diamond structure. The specimens were manufactured with two different Additive Manufacturing procedures employing various relative densities. More specifically, Material Jetting Printing (MJP) and Fused Filament Fabrication (FFF) processes were employed to investigate the performance of Acrylonitrile Butadiene Styrene (ABS) lightweight lattice structures. These structures were examined using digital microscopy in order to measure the dimensional accuracy and the surface characteristics of the utilized AM technologies. Furthermore, three-point bending tests and finite elements analyses have been applied to investigate the mechanical performance of the proposed technologies and designs as well as the influence of the relative density on the Schwarz diamond TPMS structure. The experimental results demonstrate that the investigated structure possesses a remarkable performance in respect to its weight due to the specific distribution of its material in space.
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Pellegrino, J., S. Wright, J. Ranvill und G. Amy. „Predicting membrane flux decline from complex mixtures using flow-field flow fractionation measurements and semi-empirical theory“. Water Science and Technology 51, Nr. 6-7 (01.03.2005): 85–92. http://dx.doi.org/10.2166/wst.2005.0625.
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Flow-Field Flow Fractionation (Fl-FFF) is an idealization of the cross flow membrane filtration process in that, (1) the filtration flux and crossflow velocity are constant from beginning to end of the device, (2) the process is a relatively well-defined laminar-flow hydrodynamic condition, and (3) the solutes are introduced as a pulse-input that spreads due to interactions with each other and the membrane in the dilute-solution limit. We have investigated the potential for relating Fl-FFF measurements to membrane fouling. An advection-dispersion transport model was used to provide ‘ideal’ (defined as spherical, non-interacting solutes) solute residence time distributions (RTDs) for comparison with ‘real’ RTDs obtained experimentally at different cross-field velocities and solution ionic strength. An RTD moment analysis based on a particle diameter probability density function was used to extract “effective” characteristic properties, rather than uniquely defined characteristics, of the standard solute mixture. A semi-empirical unsteady-state, flux decline model was developed that uses solute property parameters. Three modes of flux decline are included: (1) concentration polarization, (2) cake buildup, and (3) adsorption on/in pores, We have used this model to test the hypothesis—that an analysis of a residence time distribution using Fl-FFF can describe ‘effective’ solute properties or indices that can be related to membrane flux decline in crossflow membrane filtration. Constant flux filtration studies included the changes of transport hydrodynamics (solvent flux to solute back diffusion (J/k) ratios), solution ionic strength, and feed water composition for filtration using a regenerated cellulose ultrafiltration membrane. Tests of the modeling hypothesis were compared with experimental results from the filtration measurements using several correction parameters based on the mean and variance of the solute RTDs. The corrections used to modify the boundary layer mass transfer coefficient and the specific resistance of cake or adsorption layers demonstrated that RTD analysis is potentially useful technique to describe colloid properties but requires improvements.
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Nafar, Zahra, Rong Wen und Shuliang Jiao. „Visible-light optical coherence tomography-based multimodal system for quantitative fundus autofluorescence imaging“. Experimental Biology and Medicine 243, Nr. 17-18 (24.11.2018): 1265–74. http://dx.doi.org/10.1177/1535370218813529.
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Fundus autofluorescence (FAF) imaging is commonly used in ophthalmic clinics for diagnosis and monitoring of retinal diseases. Lipofuscin in the retinal pigment epithelium (RPE), with A2E as its most abundant component and a visual cycle by-product, is the major fluorophore of FAF. Lipofuscin accumulates with age and is implicated in degenerative retinal diseases. The amount of lipofuscin in RPE can be assessed by quantitative measurement of FAF. However, the currently available FAF imaging technologies are not capable of quantifying the absolute intensity of FAF, which is essential for comparing images from different individuals, and from the same individual over time. One major technical difficulty is to compensate the signal attenuation by ocular media anterior to the RPE (pre-RPE media). FAF intensity is also influenced by fluctuations in imaging conditions such as illumination power and detector sensitivity, all of which need to be compensated. In this review, we present the concept and research progress of using visible-light optical coherence tomography-based simultaneous multimodal retinal imaging to compensate signal attenuation by pre-RPE media and the influence of parameters of the acquisition system for accurate measurement of FAF intensities. Impact statement Quantitative fundus autofluorescence imaging with simultaneous visible-light optical coherence tomography-based multimodal technology has potential significant impact on the diagnosis and monitoring the progression of retinal diseases.
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Podesta, Mark, Sebastiaan M. J. J. G. Nijsten, Lucas C. G. G. Persoon, Stefan G. Scheib, Christof Baltes und Frank Verhaegen. „Time dependent pre-treatment EPID dosimetry for standard and FFF VMAT“. Physics in Medicine and Biology 59, Nr. 16 (04.08.2014): 4749–68. http://dx.doi.org/10.1088/0031-9155/59/16/4749.
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DuBois, Grant E. „Validity of early indirect models of taste active sites and advances in new taste technologies enabled by improved models“. Flavour and Fragrance Journal 26, Nr. 4 (18.02.2011): 239–53. http://dx.doi.org/10.1002/ffj.2042.
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Kakinuma, Yasuhiro, Singo Takezawa, Tojiro Aoyama, Katsutoshi Tanaka und Hidenobu Anzai. „Electric Field-Assisted Glass Polishing Using Electro-Rheological Gel Pad“. Advanced Materials Research 76-78 (Juni 2009): 319–24. http://dx.doi.org/10.4028/www.scientific.net/amr.76-78.319.
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. A polishing process, which is the final process in manufacturing optical elements, takes a long time and often depends on the experience and special skills. Development of a skill-less polishing technology and automation of its process, therefore, has been required. One of the most promising polishing technologies is Field-assisted Fine Finishing (FFF). In this study, an Electro-rheological Gel (ERG) polishing pad with one-sided patterned electrodes is developed to polish insulator materials and, moreover, a novel electric-field-assisted polishing technology for glass polishing is proposed applying this pad. The ERG polishing pad can change the polishing performance according to applied electric field due to “electro-adhesion effect”. Results of several polishing tests show that the performance of polishing a blue glass can be controlled by applying electric field to the ERG pad.
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Hooshmand, Mohammad Javad, Saeed Mansour und Amin Dehghanian. „Optimization of build orientation in FFF using response surface methodology and posterior-based method“. Rapid Prototyping Journal 27, Nr. 5 (18.05.2021): 967–94. http://dx.doi.org/10.1108/rpj-07-2020-0162.
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Purpose The advancement of additive manufacturing technologies has resulted in producing parts of high quality and reduced manufacturing time. This paper aims to achieve a simultaneous optimal solution for build time and surface roughness as the output data and also to find the best values for the input data consisting of build orientation, extrusion width, layer thickness, infill percentage and raster angle. Design/methodology/approach For this purpose, the effects of process parameters on the response variables were investigated by the design of experiments approach to develop empirical models using response surface methodology. The experimental parts of this research were conducted using an inexpensive and locally assembled fused filament fabrication (FFF) machine. A total of 50 runs for 4 different geometries, namely, cylinder, prism, 3DBenchy and twist gear vase, were performed using the rotatable central composite design, and each process parameters were investigated in two levels to develop empirical models. Also, a novel optimization method, namely, the posterior-based method, was accomplished to find the best values for the response variables. Findings The results demonstrated that not only the build orientation and layer thickness have notable effects on both response variables but also build time is dependent on extrusion width and infill percentage. Low infill percentage and high extrusion width resulted in increasing build time. By reducing layer thickness and infill percentage while increasing extrusion width, parts of high-quality surface finish and reduced built time were produced. Optimum process parameters were found to be of build direction of 0°, extrusion width of 0.61 mm, layer thickness of 0.22 mm, infill percentage of 20% and raster angle of 0°. Originality/value Through the developed empirical models and by minimizing build orientation and layer thickness, and also considerations for process parameters, parts of high-quality surface finish and reduced built time could be produced on FFF machines. To compensate for increased build time because of reduction in layer thickness, extrusion width and infill percentage must have their maximum and minimum value, respectively.
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Korotkova, A. „Adolescent Eco-Activism in Crisis“. World Economy and International Relations 65, Nr. 6 (2021): 107–18. http://dx.doi.org/10.20542/0131-2227-2021-65-6-107-118.
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Received 09.12.2020. The article analyzes the activities of the adolescent environmental community “Fridays For Future” in the context of the crisis caused by the COVID-19 pandemic. The school climate activist movement was initiated in 2018 in Sweden by 15-year-old Greta Thunberg. It has actively been gaining momentum during the two years of its existence. Thanks to the attention of the media and leading international organizations, it has acquired worldwide fame. But in 2020, due to the spread of coronavirus infection, the FFF was forced to pass the first serious test of strength. In the context of quarantine, it has lost two of its most important components. First, the increased interest of the media, which focused on covering a new burning topic, has dried up. Secondly, street demonstrations, which were the main method of the activists’ struggle, were banned. The author of the article explores actions and new ways of activity that the members of the “Fridays For Future” have adapted to their goals. As a source base for this research, the Internet resources of the movement are investigated which have been developed quite well during its existence. In addition to this network of information, the materials of the mass media that continued to monitor the activities of young climate fighters were also reviewed. In addition, the works of other researchers studying the FFF movement are involved, unfortunately, not many, since the topic is relatively new. The article concludes about the ability of such type of associations as the “Fridays For Future” to maintain stability in crisis situations. This is facilitated by the features of their network device, as well as the generational identity of their participants. The main core of the movement is young students, whose representatives have mastered the new information technologies perfectly. Thanks to this fact, they are able to quickly adjust their methods and software settings, while generally maintaining a common commitment to their goals. Acknowledgements. The article was prepared within the project “Post-Crisis World Order: Challenges and Technologies, Competition and Cooperation” supported by the grant from Ministry of science and higher education of The Russian Federation program for research projects in priority areas of scientific and technological development (Agreement № 075-15-2020-783).
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RK, Kumar, und Shah P. „‘Fifth Day Fits’ (FDF) – Biotinidase Deficiency is Probably the New Name“. Asploro Journal of Pediatrics and Child Health 2, Nr. 3 (03.01.2021): 58–61. http://dx.doi.org/10.36502/2020/asjpch.6159.
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Neonatal Seizures, the most critical of neonatal neurologic dysfunction, has aetiology of varying prognoses. The diagnosis of underlying aetiology is most critical. With use of genetic studies, better imaging technologies, better cortical electrical activity mapping and biochemical advancement, every attempt in diagnosing a cause is made.
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Budgell, Geoff, Kirstie Brown, Jason Cashmore, Simon Duane, John Frame, Mark Hardy, David Paynter und Russell Thomas. „IPEM topical report 1: guidance on implementing flattening filter free (FFF) radiotherapy“. Physics in Medicine and Biology 61, Nr. 23 (07.11.2016): 8360–94. http://dx.doi.org/10.1088/0031-9155/61/23/8360.
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