Extrusion Rate Research Articles

Blown film stability for low, medium, and high molecular weight polylactic acid and their tensile properties

Three poly (lactic acid) (PLA) resins with molecular weight (Mw) equal to 55 (3251D), 125 (L105) and 163 (LX175) kg/mol were characterized in terms of capillary viscosity, mechanical and thermal properties and used to produce blown films. The effect of temperature, extrusion rate, stretching (TUR) and blow-up (BUR) ratios were evaluated to determine the optimum processing conditions for blown films based on the bubble stability and to determine their final tensile properties. As expected, the processing temperature was the most critical parameter on the film stability. The lower Mw PLA showed limited processing stability. Stable conditions were found at higher temperature (200°C) for higher Mw. These results correlate with the PLA viscosity (melt strength). Finally, the PLA film tensile strength (TS) strongly depended on their processability. For example, 3251D and L105 required high stretching (TUR = 3.4 and 7) for maximum TS (30 and 64 MPa) with a low blow-up ratio (BUR = 1.02–1.15). However, a moderate increase in BUR (10% at TUR = 3) led to a substantial drop in TS (from 29 MPa to 21 MPa for PLA 3251D and 44 MPa–34 MPa for L105). Overall, LX175 was the most interesting resin with 49 MPa TS which was independent of the BUR and TUR used in this investigation.

Effect of 3D printing conditions and post-printing fermentation on pearl millet fortified idli.

Three-dimensional (3D) printing is an emerging technology with numerous applications in the development of novel foods to meet personalized and special dietary needs. Using 3D printing, foods with modified textures and consistency can be prepared conveniently. In this work, an indigenous rice-black gram batter was fortified with pearl millet flour and 3D printed in the in-house developed extrusion-based food printer, Controlled Additive-manufacturing Robotic Kit (CARK™). The impact of material supply composition was investigated along with optimization of different printing parameters and an in-depth analysis of post-printing fermentation kinetics was undertaken. The shape changes in the 3D printed constructs during fermentation were analyzed using a pixel-count-based image-processing technique that correlates with the change in surface area. The addition of millet flour resulted in accelerated fermentation. At 20% w/w level, better printability with higher precision and layer definition was obtained at 800 mm min-1 of printing speed, 360 rpm extrusion motor speed, and 1.22 mm nozzle diameter with an extrusion rate of 15.57 mm3 s-1 . The constructs of pearl millet flour (PMF) fortified idli batter have shown good structural stability and creep recovery. Fermentation-assisted shape change was found to be significantly influenced by infill levels. Both raw and steamed constructs with 40% infill showed around 37% lower hardness than 100% infill constructs due to a porous inner structure with reduced expansion in the surface area/volume during fermentation. The results of the study provide insights into the scope of printing fermented foods through the food-to-food fortification approach and textural modification of foods using 3D printing by varying the infill levels. © 2022 Society of Chemical Industry.

Rapid pre-explosion increase in dome extrusion rate at La Soufrière, St. Vincent quantified from synthetic aperture radar backscatter

The extrusion rate of a lava dome is a critical parameter for monitoring silicic eruptions and forecasting their development. Satellite radar backscatter can provide unique information about dome growth during a volcanic eruption when other datasets (e.g., optical, thermal, ground-based measurements, etc.) may be limited. Here, we present an approach for estimating volcanic topography from individual backscatter images. Using data from multiple SAR sensors we apply the method to the dome growth during the 2021 eruption at La Soufrière, St. Vincent. We measure an average extrusion rate of 1.8 m3s−1 between December 2020 and March 2021 before an acceleration in extrusion rate to 17.5 m3s−1 in the 2 days prior to the explosive eruption on 9 April 2021. We estimate a final dome volume of 19.4 million m3, extrapolated from the SAR sensors, with approximately 15% of the total extruded volume emplaced in the last 2 days. A possible explanation for the acceleration in extrusion rate could be the combined emptying of a conduit and reservoir of older material before the ascent of gas-rich magma in April 2021.

Comparison of in vitro Maturation Media on Cattle Oocytes after in vitro Embryo Production

The study was conducted to compare differences in vitro maturation media and their effect on subsequent in vitro embryo production. The study procedures were approved by the agricultural research council animal ethics committee (Ref no: APAEC 2020/05) and the Tshwane university of technology animal research ethics committee (Ref no: AREC 2021/08/004). Follicular fluid containing a suspension of oocytes was retrieved from ovaries through aspiration and slicing techniques. The retrieved oocytes were graded and randomly matured into four media (TCM199, Vitromat Protect, and BO IVM®) groups for 22 h, evaluated for polar body extrusion, fertilized through their respective in vitro fertilization media, and evaluated for pronucleus status. Presumptive zygotes were further cultured in vitro in their respective media, incubated for either 18 or 96 h, and evaluated for cleavage rates. The data was subjected to an appropriate analysis of variance. Student's Least Significant Differences (t-LSD) was calculated at a 5% significance level to compare means of significant treatment effects. The BO-IVM® (57.4%), TCM 199 (55.6%), and VitroMat Protect® (54.0%) recorded higher results than EGF (26.9%) for polar body formation on oocytes (P<0.05). Vitrofert® medium recorded a higher percentage (43.3%) of total fertilization rate when compared to the other media (P<0.05). VitroCleave Plus® medium recorded a higher total cleavage rate (43.3%) as compared to the other media (P<0.05). In conclusion, TCM 199, BO-IVM®, and VitroMat Protect® media rendered higher results of oocyte polar body extrusion rates compared to the EGF medium. Vitrofert® medium recorded a higher percentage (43.3%) of total fertilization rate when compared to the other media. Higher embryo development (4-8 cells and total cleavage) rates were observed in VitroCleave Plus® medium. Overall, the introduced media (VitroMat Protect®) and its media suite successfully adapted to the laboratory environment in South Africa (SA) and can therefore be adopted for optimizing the in vitro Embryo Production (IVEP) of cattle oocytes.

OSSICULOPLASTY: AUTOGRAFT VS ALLOGRAFT

Background: Chronic otitis media (COM) is defined as a perforation of the tympanic membrane with persistent drainage of pus from the middle ear lasting at least two weeks. Tympanoplasty is a surgical procedure in ENT practice which aims at removal of diseased pathology from middle ear along with reconstruction of sound conducting mechanism by reconstructing the ossicular chain with various materials. Methods:All the cases of CSOM with ossicular chain deformity were included. Ear examination was done in detail, Preoperative hearing assessment was done and Hearing loss was calculated by average air bone gap on PTA.For Auto graftstragal cartilage or incus was used andfor allograft Teflon TORP/PORP with cartilage cap was used. Results: Comparison forossiculoplasty was done by comparing its advantages and disadvantages in the terms of extrusion rate and hearing restoration in postoperative period. Overall failure rate for autologous material was 8% and for alloplastic material was 12%. Conclusion: the use of autologous graft is more advantageous in terms of surgical outcome, extrusion rate, and postoperative hearing gain.

An ionic/thermal-responsive agar/alginate wet-spun microfiber-shaped hydrogel combined with grooved/wrinkled surface patterns and multi-functions

A dual stimuli-responsive wet-spun microfiber-shaped hydrogel is prepared by injecting a hot blend of two stimuli biopolymers alginate (i.e., ionic-responsive) and agar (i.e., temperature-responsive) into a pre-cooling and metal cation containing coagulation bath. Experimental results indicate the fiber microstructure could be manipulated by the extrusion rate and cooling temperature, achieving an anisotropic shrinkage characteristic and novel grooved/wrinkled surface patterns. Importantly, the integration of metal cations (e.g., Ca2+and/or Zn2+) was confirmed to significantly improve the hydrogel mechanical properties (i.e., double networks) and enhanced blue fluorescent intensity as a typical metal-polymer complexation formed within the agar gel matrix. Moreover, the functionality-independent double networks enabled typical pH-shape memory and sustainable antibacterial properties have also been demonstrated. Therefore, combing the facile fabricating approach and multifunctionality, this study would advance the development of stimuli-responsive hydrogel microfiber for complex biomedical systems.

Combining Digital Twin and Machine Learning for the Fused Filament Fabrication Process

In this work, the feasibility of applying a digital twin combined with machine learning algorithms (convolutional neural network and random forest classifier) to predict the performance of PLA (polylactic acid or polylactide) parts is being investigated. These parts are printed using a low-cost desktop 3D printer based on the principle of fused filament fabrication. A digital twin of the extruder assembly has been created in this work. This is the component responsible for melting the thermoplastic material and depositing it on the print bed. The extruder assembly digital twin has been separated into three simulations, i.e., conjugate convective heat transfer, multiphase material melting, and non-Newtonian microchannel. The functionality of the physical extruder is controlled by a PID/PWM circuit, which has also been modelled within the digital twin to control the virtual extruder’s operation. The digital twin simulations were validated through experimentation and showed a good agreement. After validation, a variety of parts were printed using PLA at four different extrusion temperatures (180 °C, 190 °C, 200 °C, 210 °C) and ten different extrusion rates (ranging from 70% to 160%). Measurements of the surface roughness, hardness, and tensile strength of the printed parts were recorded. To predict the performance of the printed parts using the digital twin, a correlation was established between the temperature profile of the non-Newtonian microchannel simulation and the experimental results using the machine learning algorithms. To achieve this objective, a reduced order model (ROM) of the extruder assembly digital twin was developed to generate a training database. The database generated by the ROM (simulation results) was used as the input for the machine learning algorithms and experimental data were used as target values (classified into three categories) to establish the correlation between the digital twin output and performance of the physically printed parts. The results show that the random forest classifier has a higher accuracy compared to the convolutional neural network in categorising the printed parts based on the numerical simulations and experimental data.

A Case-Control Study of Titanium and Fluoroplastic Ventilation Tubes.

Background Tympanostomy ventilation tube (VT) insertion is one of the most common procedures performed in otorhinolaryngology. VTs have been proven to effectively manage otitis media (OM) with effusion (OME) and to improve the quality of life of children postoperatively. Although there are multiple types of VT shapes, materials, and sizes, few studies have investigated and compared the effects of titanium VT with those of VTs made of other materials. This study aimed to compare titanium VTs and the more commonly used fluoroplastic VTs in a retrospective, age-matched, case-control study. We studied the postoperative outcomes and rates of extrusion, infection, otorrhea, tube obstruction, and residual perforation. Methodology Medical records of patients who underwent myringotomy with VT insertion from January 2018 to December 2020 were reviewed. A total of 34 patients met the inclusion criteria, of whom 17 had undergone titanium VT insertion bilaterally (titanium group) and 17 had undergone fluoroplastic VT insertion bilaterally (control group). Both groups were followed up with regular postoperative examinations for 18 months. Results Postoperative complications were categorized as early and late complications. The most common early postoperative complication was early extrusion of VT(six months or less after insertion) (67.6%); this was documented most often in the titanium group. Other early postoperative complications included transient otorrhea (14.7%), tube blockage (8.8%), and recurrent acute otitis media (AOM) (occurring within one month from completion of therapy of AOM episode) (5.9%); these rates were similar in both groups. Late complications were not significantly variable between groups. Tympanic membrane retraction was the most common late complication (8.8%). Conclusions VT insertion is associated with the risk of complications with varying degrees. Although factors affecting the VT complication rates are multiple and various, these rates were not different between groups in this study. However, further studies including larger population samples are needed to statistically confirm these results and their generalizability.

A voxel-by-voxel method for mixing two filaments during a 3D printing process for soft-tissue replication in an anthropomorphic breast phantom

Objective. In this study, a novel voxel-by-voxel mixing method is presented, according to which two filaments of different material are combined during the three dimensional (3D) printing process. Approach. In our approach, two types of filaments were used for the replication of soft-tissues, a polylactic acid (PLA) filament and a polypropylene (PP) filament. A custom-made software was used, while a series of breast patient CT scan images were directly associated to the 3D printing process. Each phantom´s layer was printed twice, once with the PLA filament and a second time with the PP filament. For each material, the filament extrusion rate was controlled voxel-by-voxel and was based on the Hounsfield units (HU) of the imported CT images. The phantom was scanned at clinical CT, breast tomosynthesis and micro CT facilities, as the major processing was performed on data from the CT. A side by side comparison between patient´s and phantom´s CT slices by means of profile and histogram comparison was accomplished. Further, in case of profile comparison, the Pearson´s coefficients were calculated. Main results. The visual assessment of the distribution of the glandular tissue in the CT slices of the printed breast anatomy showed high degree of radiological similarity to the corresponding patient´s glandular distribution. The profile plots´ comparison showed that the HU of the replicated and original patient soft tissues match adequately. In overall, the Pearson´s coefficients were above 0.91, suggesting a close match of the CT images of the phantom with those of the patient. The overall HU were close in terms of HU ranges. The HU mean, median and standard deviation of the original and the phantom CT slices were −149, −167, ±65 and −121, −130, ±91, respectively. Significance. The results suggest that the proposed methodology is appropriate for manufacturing of anthropomorphic soft tissue phantoms for x-ray imaging and dosimetry purposes, since it may offer an accurate replication of these tissues.

Tracking the evolution of the summit lava dome of Merapi volcano between 2018 and 2019 using DEMs derived from TanDEM-X and Pléiades data

At andesitic volcanoes, effusive lava flows and dome emplacement alternate with explosive, sometimes very destructive events. It is thus crucial to obtain quantitative information on the dome volume emplaced as well as on the extrusion rate. However, steep slopes and continuous activity make it difficult to install field instruments near many volcano summits. In this study, we take advantage of two high resolution remote-sensing datasets, Pléiades (optical acquisitions in tri-stereo mode) and TanDEM-X (radar acquisitions in bistatic mode), to produce twenty Digital Elevation Models (DEMs) over the summit area of Merapi volcano, Indonesia, between July 2018 and December 2019. We calculate the difference in elevation between each DEM and a reference DEM derived from Pléiades images acquired in 2013, in order to track the evolution of the dome in the crater. Uncertainties are quantified for each dataset by a statistical analysis of areas with no change in elevation. We show that the DEMs derived from Pléiades and TanDEM-X data are consistent with each other and provide good spatio-temporal constraints on the evolution of the dome. Furthermore, the remote-sensing estimate of the lava volume is consistent with local drone measurements carried out by BPPTKG at the time of dome growth. From our DEMs, we show that the dome growth was sustained by a relatively small effusion rate of about 0.0336 ± 0.0067 m3.s−1(2900 ± 580 m3/day) from August 2018 to February 2019, when it reached a height of 40 m (± 5 m) and a volume of 0.64 Mm3 (± 0.03 Mm3). The lava dome initially grew radially, and then extended asymmetrically to the northwest and southeast starting in October 2018. From February 2019 onwards, the dome elevation remained constant, but lava was continuously emitted. Lava supply was balanced by destabilization southwards downhill producing an accumulation zone of 400 m long and maximum 15 m (± 5 m) high with a volume of 0.37 Mm3 (± 0.29 Mm3). The measured accumulation rate between February and September 2019 is 0.0094 ± 0.001 m3.s−1(810 ± 90 m3/day). In late 2019, several minor explosions partially destroyed the center of the dome. This study highlights the strong potential of the joint use of TanDEM-X and Pléiades DEMs to quantitatively monitor domes at andesitic stratovolcanoes.

Comparison of a human acellular dermal matrix and a polypropylene mesh for pelvic floor reconstruction: a randomized trial study in a rabbit model

Non-absorbable polypropylene (PP) meshes have been widely used in surgical reconstruction of the pelvic floor disorders. However, they are associated with serious complications. Human acellular dermal matrices (hADM) have demonstrated safety and efficacy in reconstructive medicine, but their suitability and efficacy at vaginal level is not known. This study compares the biological performance of PP mesh and a newly developed hADM. 20 rabbits were randomized to receive the hADM graft or the PP mesh. Grafts were surgically implanted in the abdominal wall and vagina. After 180 days, grafts were explanted and evaluated. The vaginal mesh extrusion rate was higher in the PP group (33% vs. 0%, p = 0.015). Full integration of the vaginal grafts was more frequent in the hADM group, where 35% of the grafts were difficult to recognize. In the PP group, the vaginal mesh was identified in 100% of the animals (p = 0.014). In PP group, the infiltrates had a focal distribution and were mostly located in the internal part of the epithelium, while in the hADM group, the infiltrates had a diffuse distribution. Additionally, the hADM group also presented more B-lymphocytes and less T-lymphocytes. Biomechanical analysis showed that hADM had lower resistance to stress. Moreover, PP mesh stiffness and elasticity were higher. Then, hADM is associated with fewer clinical complications, as well as better tissue integration. However, it shows greater incorporation into the surrounding native tissue, especially in the vaginal location, undergoing a reduction in its biomechanical properties 6 months after implantation.

Three-Dimensional Printing of Ultrasoft Silicone with a Functional Stiffness Gradient.

A methodology for three-dimensionally printing ultrasoft silicone with a functional stiffness gradient is presented. Ultraviolet-cure silicone was deposited via two independently controlled extruders into a thixotropic, gel-like, silicone oil-based support matrix. Each extruder contained a different liquid silicone formulation. The extrusion rates were independently varied during printing such that the combined selectively deposited material contained different ratios of the two silicones, resulting in localized control of material stiffness. Tests to validate the process are reported, including tensile testing of homogeneous cubic specimens to quantify the range of material stiffness that could be printed, indentation testing of cuboid specimens to characterize printed stiffness gradients, and vibratory testing of synthetic multilayer vocal fold (VF) models to demonstrate that the method may be applied to the fabrication of biomechanical models for voice production research. The cubic specimens exhibited linear stress-strain data with tensile elasticity modulus values between 1.11 and 27.1 kPa, more than a factor of 20 in stiffness variation. The cuboid specimens exhibited material variations that were visually recognizable and quantifiable via indentation testing. The VF models withstood rigorous phonatory flow-induced vibration and exhibited vibratory characteristics comparable to those of previous models. Overall, while process refinements are needed, the results of these tests demonstrate the ability to print ultrasoft silicone with stiffness gradients.

Age-related SUMOylation of PLK1 is essential to meiosis progression in mouse oocytes.

Polo like kinase 1 (PLK1) is a protein kinase involved in regulating the spindle assembly and cell cycle control in mammalian oocytes. SUMOylation, one way of post-translational modification, regulates oocyte meiosis by controlling several substrates. However, the relation between PLK1 and SUMOylation in oocytes is still unknown. In this study, we investigated that whether PLK1 was modified by SUMOylation in oocytes and its potential relationship with age-related meiotic abnormalities. We showed that PLK1 had colocalization and protein interaction with Small Ubiquitin-Like Modifier (SUMO)-1 and SUMO-2/3 in mouse oocytes, indicating that PLK1 could be modified by SUMO-1 and SUMO-2/3. Overexpression of PLK1 SUMOylation site mutants PLK1K178R and PLK1K191R caused the increase of the abnormal spindle rate of oocytes and the decline of the first polar body extrusion rate with the abnormal localization of PLK1, suggesting that the SUMOylation modification of PLK1 is essential for normal meiosis in oocytes. Compared with young mice, the expression of PLK1 protein increased and the expression of SUMO-1 and SUMO-2/3 protein decreased in the oocytes of aged mice, indicating that the SUMOylation of PLK1 might be related to the mouse aging. Therefore, our data suggested that PLK1 could be SUMOylated by SUMO-1 and SUMO-2/3 in mouse oocytes and SUMOylation of PLK1 regulated the meiosis progression of oocytes which was related with aging.

Adverse PFAS effects on mouse oocyte in vitro maturation are associated with carbon-chain length and inclusion of a sulfonate group.

Per- and polyfluoroalkyl substances (PFAS) are man-made chemicals that are widely used in various products. PFAS are characterized by their fluorinated carbon chains that make them hard to degrade and bioaccumulate in human and animals. Toxicological studies have shown PFAS toxic effects: cytotoxicity, immunotoxicity, neurotoxicity, and reproductive toxicity. However, it is still unclear how the structures of PFAS, such as carbon-chain length and functional groups, determine their reproductive toxicity. By using a mouse-oocyte-in-vitro-maturation (IVM) system, we found the toxicity of two major categories of PFAS, perfluoroalkyl carboxylic acid (PFCA) and perfluoroalkyl sulfonic acid (PFSA), is elevated with increasing carbon-chain length and the inclusion of the sulfonate group. Specifically, at 600 μM, perfluorohexanesulfonic acid (PFHxS) and perfluorooctanesulfonic acid (PFOS) reduced the rates of both germinal-vesicle breakdown (GVBD) and polar-body extrusion (PBE) as well as enlarged polar bodies. However, the shorter PFSA, perfluorobutanesulfonic acid (PFBS), and all PFCA did not show similar adverse cytotoxicity. Further, we found that 600 μM PFHxS and PFOS exposure induced excess reactive oxygen species (ROS) and decreased mitochondrial membrane potential (MMP). Cytoskeleton analysis revealed that PFHxS and PFOS exposure induced chromosome misalignment, abnormal F-actin organization, elongated spindle formation, and symmetric division in the treated oocytes. These meiotic defects compromised oocyte developmental competence after parthenogenetic activation. Our study provides new information on the structure-toxicity relationship of PFAS.

Peroxiredoxin 4 secreted by cumulus cells ameliorates the maturation of oocytes in vitro

BackgroundPeroxiredoxin 4 (Prdx4) in the endoplasmic reticulum (ER) is the only secretory member of the antioxidant Prdx family. Our previous studies demonstrated that Prdx4 in cumulus cells (CCs) ameliorated the maturation of oocytes in vitro and enhanced oocyte developmental competence by preventing CCs apoptosis caused by oxidative stress (OS) through gap junctions. In this study, we aimed to determine whether Prdx4 released by CCs can repair meiotic defects in mouse oocytes by co-culturing immature (germinal vesicle) oocytes with CCs from mature oocytes in the absence of gap junctions. ResultsThe OS-induced meiotic defects in mouse oocytes were impeded by co-culture with CCs, as evidenced by the increased first polar body (PB1) extrusion rate and decreased ROS level. CCs increased Prdx4 expression and lowered IRE1α, Bip expression in H2O2-treated oocytes. After knockdown of Prdx4 expression in CCs, the rate of PB1 extrusion in the oocytes was significantly reduced to the level detected in H2O2 group, and ER stress was not alleviated. CO-IP and immunofluorescence co-localization experiments demonstrated that Prdx4 interacted with PDIA6 in the oocytes and the Pearson's R value was 0.69 calculated using ImageJ. ConclusionsCumulus cells can promote the maturation of oocytes in vitro by secreting Prdx4 in a paracrine manner and serve as a promising therapeutic antioxidant for improving the quality of oocytes, especially aging oocytes, in clinical in vitro maturation (IVM).

Optimization of methacrylated gelatin /layered double hydroxides nanocomposite cell-laden hydrogel bioinks with high printability for 3D extrusion bioprinting.

Layered double hydroxides (LDHs) offer unique source of inspiration for design of bone mimetic biomaterials due to their superior mechanical properties, drug delivery capability and regulation cellular behaviors, particularly by divalent metal cations in their structure. Three-dimensional (3D) bioprinting of LDHs holds great promise as a novel strategy thanks to highly tunable physiochemical properties and shear-thinning ability of LDHs, which allow shape fidelity after deposition. Herein, we introduce a straightforward strategy for extrusion bioprinting of cell laden nanocomposite hydrogel bioink of gelatin methacryloyl (GelMA) biopolymer and LDHs nanoparticles. First, we synthesized LDHs by co-precipitation process and systematically examined the effect of LDHs addition on printing parameters such as printing pressure, extrusion rate, printing speed, and finally bioink printability in creating grid-like constructs. The developed hydrogel bioinks provided precise control over extrudability, extrusion uniformity, and structural integrity after deposition. Based on the printability and rheological analysis, the printability could be altered by controlling the concentration of LDHs, and printability was found to be ideal with the addition of 3 wt % LDHs. The addition of LDHs resulted in remarkably enhanced compressive strength from 652 kPa (G-LDH0) to 1168 kPa (G-LDH3). It was shown that the printed nanocomposite hydrogel scaffolds were able to support encapsulated osteoblast survival, spreading, and proliferation in the absence of any osteoinductive factors taking advantage of LDHs. In addition, cells encapsulated in G-LDH3 had a larger cell spreading area and higher cell aspect ratio than those encapsulated in G-LDH0. Altogether, the results demonstrated that the developed GelMA/LDHs nanocomposite hydrogel bioink revealed a high potential for extrusion bioprinting with high structural fidelity to fabricate implantable 3D hydrogel constructs for repair of bone defects.

Coupled thermo-mechanical numerical model to minimize risk in large-format additive manufacturing of thermoplastic composite designs

The collapse of deposited thermoplastic composite material under self-weight presents a risk in large-format extrusion-based additive manufacturing. Two critical processing parameters, extrusion temperature and deposition rate, govern whether a deposited layer is stable and bonds properly with the previously deposited layer. Currently, the critical parameters are determined via a trial-and-error approach. This research work uses a simplified physics-based numerical simulation to determine a suitable combination of the parameters that will avoid the collapse of the deposited layer under self-weight. The suitability of the processing parameters is determined based on the maximum plastic viscous strains computed using a sequentially coupled thermo-mechanical numerical model. This computational tool can efficiently check if a combination of temperature and extrusion rate causes layer collapse due to self-weight, and hence minimize the manufacturing risk of large-format 3D-printed parts.

Neural networks and NARXs to replicate extrusion simulation in digital twins for fused filament fabrication

In this work we propose the use of nonlinear autoregressive models with exogenous variables (NARXs), powered by dynamic recurrent neural networks, to replicate the results of a previously developed, complex simulation of the extrusion process in fused filament fabrication. The NARXs predict extrusion rate of the extrudate and compression force acting on the filament with an average discrepancy of 0.12 % with respect to the original simulation, but at a fraction of the computational time (0.1 s of the NARX vs. 600 s needed by the original simulation to process the same one-minute time interval). In addition to illustrating how NARXs can be created to mimic an existing simulation, in this work we show how the NARXs can be physically connected to the sensors of a real FFF machine, thus creating an effective digital twin of the extrusion process, useful to support real-time decision making by an AI machine controller. Finally, we show how the implemented digital twin can be used for in-process monitoring, bringing as example the automated detection of an extrusion clogging event.

A filament 3D printing approach for CT-compatible bone tissues replication

PurposeThe aim of this study is the development of a methodology for manufacturing 3D printed anthropomorphic structures, which mimic the X-ray properties of the human bone tissue. MethodsA mixing approach of two different materials is proposed for the fabrication of a radiologically equivalent hip bone for an anthropomorphic abdominal phantom. The materials employed for the phantom were polylactic acid (PLA) and Stonefil, while a custom-made dual motor filament extrusion setup and a custom-made software associating medical images directly with the 3D printing process were employed. ResultsThree phantoms representing the hip bone were 3D printed utilizing two filaments under three different printing scenarios. The phantoms are based on a patient’s abdominal CT scan images. Histograms of CT scans of the printed hip bone phantoms were calculated and compared to the original patient’s hip bone histogram, demonstrating that a constant mixing composition of 30% Stonefil and 70% PLA with 0.0375 extrusion rate per voxel (93.75% flow for fulfilling a single voxel) for the cancellous bone, and using 100% Stonefil with 0.04 extrusion rate per voxel (100% flow) for the cortical bone results in a realistic anatomy replication of the hip bone. Reproduced HU varied between 700 and 800, which are close to those of the hip bone. ConclusionsThe study demonstrated that it is possible to mix two different filaments in real-time during the printing process to obtain phantoms with realistic and radiographically bone tissue equivalent attenuation. The results will be explored for manufacturing a CT-compatible abdominal phantom.

Printing Parameters of Sugar/Pectin Jelly Candy and Application by Using a Decision Tree in a Hot-Extrusion 3D Printing System

This study aims to obtain a desirable 3D printing product based on the knowledge of the material and suitable printing parameters. This study used high-methoxy pectin (HMP) as the ingredient of pectin jelly candy to understand the effect of different pectin concentrations and printing parameters (nozzle height, extrusion rate, printing layer height, nozzle movement speed, and nozzle diameter). Machine learning was used to learn and analyze the data of different 3D printing parameters to find out a suitable parameter. Rheological analysis revealed that a 16% pectin (w/v) concentration had the height of G′ and G″, and all pectin jelly candy showed the characteristic of shearing thinning. A parameter analysis decision tree revealed that the pectin concentration of 12–14% (w/v), printing layer height below 1.5 mm, extrusion rate below 0.305 mm3/s, nozzle height above 0.5 mm, and printing rate of 5–10 mm were able to allow pectin jelly candy to be printed with an error below 5%. Machine learning helps researchers find appropriate parameters and reach the design of molding height quickly, and it helps them discuss how molecule interaction causes different 3D printing results.