Printing Model Research Articles

An Efficient Self‐supporting Infill Structure for Computational Fabrication

AbstractEfficiently optimizing the internal structure of 3D printing models is a critical focus in the field of industrial manufacturing, particularly when designing self‐supporting structures that offer high stiffness and lightweight characteristics. To tackle this challenge, this research introduces a novel approach featuring a self‐supporting polyhedral structure and an efficient optimization algorithm. Specifically, the internal space of the model is filled with a combination of self‐supporting octahedrons and tetrahedrons, strategically arranged to maximize structural integrity. Our algorithm optimizes the wall thickness of the polyhedron elements to satisfy specific stiffness requirements, while ensuring efficient alignment of the filled structures in finite element calculations. Our approach results in a considerable decrease in optimization time. The optimization process is stable, converges rapidly, and consistently delivers effective results. Through a series of experiments, we have demonstrated the effectiveness and efficiency of our method in achieving the desired design objectives.

Instant trachea reconstruction using 3D-bioprinted C-shape biomimetic trachea based on tissue-specific matrix hydrogels

Currently, 3D-bioprinting technique has emerged as a promising strategy to offer native-like tracheal substitutes for segmental trachea reconstruction. However, there has been very limited breakthrough in tracheal repair using 3D-bioprinted biomimetic trachea owing to the lack of ideal bioinks, the requirement for precise structural biomimicking, and the complexity of multi-step surgical procedures by mean of intramuscular pre-implantation. Herein, we propose a one-step surgical technique, namely direct end-to-end anastomosis using C-shape 3D-bioprinted biomimetic trachea, for segmental trachea defect repair. First, two types of tissue-specific matrix hydrogels were exploited to provide mechanical and biological microenvironment conducive to the specific growth ways of cartilage and fibrous tissue respectively. In contrast to our previous O-shape tracheal design, the tubular structure of alternating C-shape cartilage rings and connecting vascularized-fibrous-tissue rings was meticulously designed for rapid 3D-bioprinting of tracheal constructs with optimal printing paths and models. Furthermore, in vivo trachea regeneration in nude mice showed satisfactory mechanical adaptability and efficient physiological regeneration. Finally, in situ segmental trachea reconstruction by direct end-to-end anastomosis in rabbits was successfully achieved using 3D-bioprinted C-shape biomimetic trachea. This study demonstrates the potential of advanced 3D-bioprinting for instant and efficient repair of segmental trachea defects.

World's First Long-Term Colorectal Cancer Model by 3D Bioprinting as a Mechanism for Screening Oncolytic Viruses.

Long-term modelization of cancer as it changes in the human body is a difficult goal, particularly when designing and testing new therapeutic strategies. This becomes even more difficult with metastasis modeling to show chemotherapeutic molecule delivery directly to tumoral cells. Advanced therapeutics, including oncolytic viruses, antibody-based and cell-based therapies are increasing. The question is, are screening tests also evolving? Next-generation therapeutics need equally advanced screening tests, which whilst difficult to achieve, are the goal of our work here, creating models of micro- and macrotumors using 3D bioprinting. We developed advanced colorectal cancer tumor processing techniques to provide options for cellular expansion, microtumor printing, and long-term models, which allow for the evaluation of the kinetics of penetration testing, therapeutic success, targeted therapies, and personalized medicine. We describe how we tested tumors from a primary colorectal patient and, applying 3D bioprinting, matured long-term models for oncolytic metastatic screening. Three-dimensional microtumors were kept alive for the longest time ever recorded in vitro, allowing longitudinal studies, screening of oncolytic viruses and realistic modelization of colorectal cancer. These 3D bioprinted models were maintained for around 6 months and were able to demonstrate the effective delivery of a product to the tumoral environment and represent a step forward in therapeutic screening.

The sustainable potential of hydrokinetic turbines in the Amazon basin

The Amazon, rich in biodiversity and natural resources, seeks renewable energy sources to minimize environmental impacts and reduce dependence on non-renewable sources. Hydrokinetic turbines emerge as a promising alternative by making it possible to convert the kinetic energy of river currents into electricity, without the need for dams. This study focuses on exploring the sustainable potential of hydrokinetic turbines in the Amazon region. For this, a prototype hydroelectric power plant that uses a hydrokinetic turbine was developed, and the feasibility of this technology as a renewable energy source was examined. The research included 3D modeling and propeller printing for the prototype, using materials such as carbon steel and 3D printing. The electrical components were dimensioned according to current technical standards, including cables, circuit breakers, batteries and converters. The methodology included tests on the real environment of a river in the Amazon region, evaluating the power generation capacity and the adaptability of the system to local conditions. The results demonstrated that the prototype is capable of producing electrical energy efficiently, taking advantage of the strength of river currents. The flexibility of the blades allowed adjustments according to the geometry of the watercourse, increasing the versatility of the system. In addition, the modular approach of turbines has shown promise for scalability and installation in different scenarios. This study contributes to the understanding of the potential of hydrokinetic turbines in the Amazon region, offering a renewable solution for electricity generation. The combination of technologies such as 3D printing, structural and electrical modeling has resulted in a prototype adaptable to local conditions, with the potential to provide clean energy to riverine communities, reducing dependence on non-renewable sources and promoting the sustainable development of the region.

Application effect of head-mounted mixed reality device combined with 3D printing model in neurosurgery ventricular and hematoma puncture training

BackgroundThe purpose of this study was to explore the applicability of application effect of head-mounted mixed reality (MR) equipment combined with a three-dimensional (3D) printed model in neurosurgical ventricular and haematoma puncture training.MethodsDigital Imaging and Communications in Medicine (DICOM) format image data of two patients with common neurosurgical diseases (hydrocephalus and basal ganglia haemorrhage) were imported into 3D Slicer software for 3D reconstruction, saved, and printed using 3D printing to produce a 1:1-sized head model with real person characteristics. The required model (brain ventricle, haematoma, puncture path, etc.) was constructed and imported into the head-mounted MR device, HoloLens, and a risk-free, visual, and repeatable system was designed for the training of junior physicians. A total of 16 junior physicians who studied under this specialty from September 2020 to March 2022 were selected as the research participants, and the applicability of the equipment and model during training was evaluated with assessment score sheets and questionnaires after training.ResultsAccording to results of the assessment and questionnaire, the doctors trained by this system are more familiar with the localization of the lateral anterior ventricle horn puncture and the common endoscopic surgery for basal ganglia haemorrhage, as well as more confident in the mastery of these two operations than the traditional training methods.ConclusionsThe use of head-mounted MR equipment combined with 3D printing models can provide an ideal platform for the operation training of young doctors. Through holographic images created from the combination of virtual and real images, operators can be better immersed in the operation process and deepen their understanding of the operation and related anatomical structures. The 3D printed model can be repeatedly reproduced so that doctors can master the technology, learn from mistakes, better achieve the purpose of teaching and training, and improve the effect of training.

Use of reconstruction plates prebent on three-dimensional models to reduce the complications of mandibular reconstruction

Background/purposeThough the gold standard method for mandible reconstruction of the defect from segmental mandibulectomy is by osseous flap or graft, using reconstruction plates is still indicated in some cases. Traditionally, the plate is bended immediately after the segmental mandibulectomy by freehand. However, it's difficult to fit well to the original position of mandible, which may result in more complications. This study therefore aimed to investigate whether using prebent plates on computer-aided 3D printing models could reduce the complication rate. Materials and methodsPatients who received mandible reconstruction by reconstruction plate from 2018 to 2022 were enrolled and evaluated in this study. The data, including demographics, indications for surgery, pre-existed preoperative and postoperative therapies, classification of defects, and postoperative outcomes were collected and analyzed. ResultsA total of 52 patients were enrolled in our study. The prebent group exhibited a significantly lower complication rate than that of the immediately bent group (P = 0.012). Other risk factors of plate complications included postoperative adjuvant radiotherapy (P = 0.017) and previous surgery (P = 0.047). The complication-free survival rate was also better in the prebent group in a 3-year follow-up period (P = 0.012). ConclusionPrebent plates on computer-aided printing models proved to be an effective approach to reduce the complications for mandibular reconstruction in segmental mandibulectomy.

Comparison of dimensional accuracy of 3D printing model for clear aligner among various orientation types and hollow types

ABSTRACT Purpose The objective of this study was to investigate the effect of printing protocol focusing upon the accuracy of 3D-printed dental models. Materials and Methods In total, 6 groups of 10 identical maxillary dental models (Formlabs dental model resin) were produced with a stereolithography (SLA)-based 3D printer using 6 printing protocols, Group 1: Hollow/Horizontal (HH), Group 2: Hollow/Oblique (HO), Group 3: Hollow/Vertical (HV), Group 4: Non-hollow/Horizontal (NHH), Group 5: Non-hollow/Oblique (NHO) and Group 6: Non-hollow/Vertical (NHV). Deviation analysis (GOM Inspect) using the best-fit algorithm was conducted to assess accuracy. Trueness and precision of 5 tooth types which were further classified by 3 surface points on anterior teeth and 5 surface points on posterior teeth, were calculated. Thereafter, Kruskal–Wallis was conducted to determine if there were any differences in trueness/precision among the 6 printing protocols. Results Accuracy of clear aligner models showed significant differences (p < .05) among the 6 printing protocols. Majority of values were within clinically acceptable limits (<0.2 mm) except for first molars and second molars. HV showed significant worst accuracy while NHH was the best printing protocol. Other groups (HH/NHV/HO/NHO) were ranked in middle. Inaccuracy was varied depending on tooth type and surface points. Second molars showed greatest defects at significant level in all printing groups. Color surface maps of 3D model superimposition demonstrated non-uniform deviations. Conclusions The printing protocols with differences in hollow types and printing orientations can significantly affect the dimensional accuracy of 3D printed models for clear aligner. Overall deviations showed location-specific deviations.

АВТОМАТИЗИРОВАННАЯ СИСТЕМА ПОДГОТОВКИ 3D МОДЕЛЕЙ К ПРОИЗВОДСТВУ ИЗДЕЛИЙ НА АДДИТИВНЫХ УСТАНОВКАХ

The problem of the duration of the preparation of models for 3D printing is considered, in order to reduce the complexity of the process of preparing the model for production at additive plants and the production itself. Connection and data exchange via socket between the server and the CuraEngine engine are described. The results of the duration of preparation of 3D models for printing with and without the proposed system are compared.

Improving physio-mechanical and biological properties of 3D-printed PLA scaffolds via in-situ argon cold plasma treatment

As a bone tissue engineering material, polylactic acid (PLA) has received significant attention and interest due to its ease of processing and biocompatibility. However, its insufficient mechanical properties and poor wettability are two major drawbacks that limit its extensive use. For this purpose, the present study uses in-situ cold argon plasma treatment coupled with a fused deposition modeling printer to enhance the physio-mechanical and biological behavior of 3D-printed PLA scaffolds. Following plasma treatment, field emission scanning electron microscopy images indicated that the surface of the modified scaffold became rough, and the interlayer bonding was enhanced. This resulted in an improvement in the tensile properties of samples printed in the X, Y, and Z directions, with the enhancement being more significant in the Z direction. Additionally, the root mean square value of PLA scaffolds increased (up to 70-fold) after plasma treatment. X-ray photoelectron spectroscopy analysis demonstrated that the plasma technique increased the intensity of oxygen-containing bonds, thereby reducing the water contact angle from 92.5° to 42.1°. The in-vitro degradation study also demonstrated that argon plasma treatment resulted in a 77% increase in PLA scaffold degradation rate. Furthermore, the modified scaffold improved the viability, attachment, and proliferation of human adipose-derived stem cells. These findings suggest that in-situ argon plasma treatment may be a facile and effective method for improving the properties of 3D-printed parts for bone tissue engineering and other applications.

(Digital Presentation) PLA Additive Manufactured Electrode for Non-Enzymatic Electrochemical Detection of Urea in Human Urine

The fourth industrial revolution is currently seeing the emergence of additive manufacturing, also known as 3D printing, which has the potential to transform current manufacturing procedures. In this work we present an electrochemical sensor for detection of urea in human urine by using the 3D-printed electrode. A commercial 3D conductive filament of carbon black and polylactic acid (PLA) is used by the fused deposition modeling (FDM) printer for the manufacturing of the electrode. The mechanical strength of the electrode was analyzed by performing the tensile, flexural, and impact tests using a Universal testing Machine. The fracture failures were studied using the Scanning Electron Microscope. The stability and reproducibility of the electrode is analyzed by performing fifteen repeated cyclic voltammetric responses to 0.1M of uric acid. The 3D printed electrode offered the detection limit of uric acid with 1.18 μM and a sensitivity of 97.9 nA μM-1. Keywords: 3D-Printing, Additive Manufacturing, Polylactic acid, Uric Acid and Electrochemical Sensor

Enhanced mechanical characteristics of polylactic acid/tamarind kernel filler green composite filament for 3D printing

AbstractThe significance and interest of printing green composites in three dimensions have recently grown, especially in light of the possibility of reusing waste to produce green fillers that can reduce the cost of biopolymers without compromising their processability and performance outcomes from a mechanical and environmental perspective. In the current work, the kernel powder obtained from the seeds of Tamarindus indica (TI) was added to polylactic acid (PLA) and extruded as a filament in the single screw extruder. It was then printed using an open source Fused Deposition Modeling printer and investigated for its density, mechanical, surface, and morphological characteristics. It was found that the composite performed better when the filler concentration was maintained at 2%, but when it went beyond that, the performance depreciated because of the rapid rise in material voids. When compared with a neat PLA matrix, 2% TI filler offered better overall strength, with increments of 12.64%, 19.87%, and 15.57% in tensile, compression, and flexural strength, respectively. The addition of TI filler was found to promote crystallization within the PLA matrix, leading to a higher degree of crystallinity which have contributed to higher strength. The morphological study demonstrated that the occurrence of uniform filler distribution and inter‐layer randomized bonding at 2% TI/PLA offered superior strength, whereas at higher TI concentrations it led to pullout and delamination. On the other hand, the hardness of the composite increased proportionally to the concentration of the fillers.

Evaporation of Volatile Solvents to Characterize the Aging of Inkjet Inks for Forensic Purposes Studied by Thermal Microdesorption and Gas Chromatography-Mass Spectrometry (GC-MS)

Evaporation of various solvents in inkjet printouts on paper text was studied by thermal microdesorption in combination with gas chromatography-mass spectrometry (GC-MS). Inks from several models of printers and from several manufacturers were studied. The thermal microdesorption at 200 °C as well as the fractionated microdesorption at three temperatures were employed. The following solvents were found in the examined printouts: diethylene glycol, glycerol, 2-pyrrolidinone, 2-ethyl 2-hydroxymethyl 1,3-propanediol, triethylene glycol, butoxyethoxyethanol, and 1,5-pentanediol. On aging, the quantity of these solvents decreased rapidly and generally could be detected in the prints only for several months after the deposition. In prints more than two years old, no or only traces of volatile solvents were found by this method. This is important for forensic analysis of documents produced by inkjet printers. The method can reveal that a document is fresh and not as old as given in the questioned document.

A 2D numerical model of 3D concrete printing including thixotropy

Additive Manufacturing (AM) techniques are increasingly drawing interest in the construction sector since they can offer new architectural possibilities while improving the accuracy and the sustainability of the construction process. Among these techniques, 3D Concrete Printing (3DCP) is probably the most established and its future role in lowering the environmental impact of the building industry is under deep investigation. 3DCP main advantages, which are linked to the capacity of building optimized structural shapes, without the need for formworks and in very short times, are however still limited by the lack of knowledge and regulation. It is therefore necessary to provide designers with more advanced design tools to fully unlock the potential of 3DCP. This work presents a numerical model of 3DCP, which realistically simulates the extrusion and layer deposition phases. The model assumes that fresh concrete can be treated as a homogeneous viscous fluid. The problem is then governed by the Navier-Stokes equations, which are solved in a Lagrangian framework with the Particle Finite Element Method (PFEM). A Bingham law, modified to include thixotropic effects, is employed to accurately reproduce the material rheological behaviour at the early ages. The model is then applied to simulate a simple printing scenario, for which the fundamental experimental data is available in the literature, to assess the role of thixotropy in the printing process. The results show how thixotropy has a crucial effect in limiting the overall shape deformation and in avoiding the early compression failure of the bottom layers. In this view, the developed model can be applied to optimize the printing parameters with respect to the rheological properties and could also suggest how to improve the toolpath and the printing times for a given structure.

Experimental Study on the Influence of Model Parameters on the Dimensional Deviation of Printed Parts

Not being affected by the structural complexity of the print model is one of the outstanding features of 3D printing, but model parameters have an important influence on the dimensional accuracy of the printed parts. In order to explore the influence of model parameters on dimensional deviation, on the basis of designing experimental models and carrying out printing experiments, we have studied the effect of three model parameters (placement method, two-dimensional contour components, and model inclination) on printing accuracy through the dimensional deviation rate. It has been found that the inclination angle of the model mainly affects the dimensional error in the height direction; different models can change the filling method of the cross-section contour from a curve to a straight line by changing the placement method, which can reduce the dimensional error of the two-dimensional contour of the model; the contour composed of linear elements has a lower deviation rate than the contour composed of curved elements.

Anomalous venoatrial connections – CT and MRI assessment

Abnormal venous atrial (VA) connections present a congenital heart disease (CHD) challenge for pediatric cardiologists. Fully anatomical evaluation is very difficult in prenatal and perinatal follow-up, but it has a profound impact on surgical correction and outcome. The echocardiogram is first-line imaging and represents the gold standard tool for simple abnormal VA connection. CT and MRI are mandatory for more complex heart disease and “nightmare cases”. 3D post-processing of volumetric CT and MRI acquisition helps to clarify anatomical relationships and allows for the creation of 3D printing models that can become crucial in customizing surgical strategy.Our article describes a ten-year (2013–2022) tertiary referral CHD center of abnormal AV connections investigated with CT and MRI, illustrating most of these complex diseases with the help of volume rendering (VR) or multiplanar reconstructions (MPR). The nightmarish cases will also be addressed due to the complex cardiovascular arrangement that requires a challenging surgical solution for correction along with the post-surgical complications.

A Generalized and Efficient Control-Oriented Modeling Approach for Vibration-Prone Delta 3D Printers Using Receptance Coupling

Delta 3D printers can significantly increase throughput in additive manufacturing by enabling faster and more precise motion compared to conventional serial-axis 3D printers. Further improvements in motion speed and part quality can be realized through model-based feedforward vibration control, as demonstrated on serial-axis 3D printers. However, delta machines have not benefited from model-based controllers because of the difficulty in accurately modeling their position-dependent, coupled nonlinear dynamics. In this paper, we propose an efficient framework to obtain accurate linear parameter-varying models of delta 3D printers at any position within their workspace from a few frequency response measurements. We decompose the dynamics into two sub-models&#x2013;(1) an experimentally-identified sub-model containing decoupled vibration dynamics; and (2) an analytically-derived sub-model containing coupled dynamics&#x2013;which are combined into one using receptance coupling. We generalize the framework by extending the analytical model of (2) to account for differing mass profiles and dynamic models of the printer&#x2019;s end-effector. Experiments demonstrate reasonably accurate predictions of the position-dependent dynamics of a commercial delta printer, augmented with a direct drive extruder, at various positions in its workspace. <i>Note to Practitioners</i>&#x2014;This work aims to equip high-speed 3D printers, like delta machines, with model-based controllers to complement their speed with high-accuracy. Due to the coupled kinematic chains of the delta, complex control methodologies, some of which require real-time state measurements, are often used to achieve satisfactory control performance. Our modeling approach provides an efficient methodology for obtaining accurate linear models without the need for real-time measurements, thus enabling practitioners to design linear model-based feedforward controllers to achieve the high throughput and accuracy desired in additive manufacturing (AM). The models we develop in this paper are intended for use with feedforward vibration compensation methods, which can be beneficial for both industrial-scale AM machines that have high-powered servo motors and feedback controllers, as well as consumer-grade AM machines which use stepper motors in feedforward control.

Prediction model and compensation method for curing shrinkage of inkjet 3D printing parts

Inkjet 3D printing has huge potential for applications in electronics printing, ceramic printing, and other fields, primarily due to the excellent dimensional accuracy of printed products, which is particularly important for device performance. However, in inkjet 3D printing, the fusion and solidification of droplets can cause the samples to shrink in various directions, resulting in a deviation from the designed target size, and subsequently affecting the performance of the part. In this study, the curing shrinkage behavior of parts in inkjet 3D printing is examined. First, a shrinkage model of the droplet element is established using the finite element method in accordance with the material parameters, and the linear shrinkage rates of different droplet groups are obtained. A curing shrinkage prediction model of the printed parts is then established, and the size and shape of the cured parts are predicted accordingly. A height calculation model of the printed parts is established according to the concept of volume conservation, and the height prediction of the printed parts is realized according to the number of printed layers and their resolution. An approach for compensation of the print model graphic layers is developed using the established prediction model. Experiments using two printing materials with different degrees of shrinkage are conducted to verify the feasibility of this method. The results indicate that the proposed curing shrinkage prediction model can seamlessly capture the curing shrinkage behavior of printed parts for materials with different shrinkages. Furthermore, after shrinkage, the model-based print compensation method achieves the measured sizes that are closer to the target size than that without compensation. The dimensions of inkjet 3D printed parts can be accurately controlled using this method.

Design of a 2RRU-RRS Parallel Kinematic Mechanism for an Inner-Cavity Machining Hybrid Robot

Abstract This article presents a hybrid robot for machining the inner cavity of large-scale workpiece, and it is composed of three parts: a mobile device with 1T degree-of-freedom (DoF), a serial module with 1R1T DoFs, and a 2RRU-RRS parallel kinematic mechanism (PKM) with 2R1T DoFs. The 2RRU-RRS PKM has some advantages with a folding structure, only one S joint, two certain rotational axes, and all the fixed actuators. In this article, the conceptual design, theoretical kinematic and dynamic modeling, performance evaluation, and optimization of the parallel system are investigated. A 3D printing model is built to demonstrate the application potential. This article plays an exemplary role in the design of inner-cavity machining hybrid robots.

3D PRINTING AND AUGMENTED REALITY: THE PROJECT FOR THE SECOND COMPETITION FOR THE ITALIAN PARLIAMENT BY ERNESTO BASILE

Abstract. The project for the second competition for the Parliament of the Kingdom of Italy, drawn up between 1888 and 1889 sees Ernesto Basile (Palermo 1857-1932) as winner ex aequo. Basile's project envisages the construction of a large monumental building (182.70 m by 171.40 m), in which the three halls, the Chamber, the Senate and the Royal Sessions Hall, develop around a large central courtyard; it will not be realized due to the fall of the Crispi government in 1891, but presents, in embryo, solutions adopted in the expansion of Palazzo Montecitorio (1903 - 1918), entrusted to Basile, in which the Chamber of Deputies, still existing today, is may consider “a sort of budding, from the organism of his second Parliament Building” (Mauro, Sessa 2000b).The original drawings are kept and cataloged in the Basile Endowment of the Scientific Collections of the Department of Architecture of the University of Palermo, edited by Professor Ettore Sessa (Mauro, Sessa, 2000a; Sessa, 2014, Mauro, Sessa, 2015).In a first phase, the conjectural reconstruction and digital modeling was carried out (Avella, 2020), and in a second phase, a first 3D printing model was created, limited to the main front, which involved the design of the decomposition and assembly according to criteria respectful of architectural parties (Avella, 2021).This work presents the progress of the work, extended to the bodies containing the Chamber of Deputies and that of the Senate and the integration with Augmented Reality systems, in view of the future permanent exhibition at the premises of the Basile Endowment. The integration with Augmented Reality visualization systems stems from the desire to allow the observer to visualize the external envelope of the physical model and the internal spaces of the parliamentary halls.

Research on the printing mechanism of electrohydrodynamic satellite-free droplets in pulsed voltage

Electrohydrodynamic (EHD) drop-on-demand (DOD) printing in pulsed voltage is a very promising technology for additive manufacturing at the micro- and nanoscale. However, jet/meniscus retraction during DOD printing creates additional satellite droplets, which can lead to blurred print patterns and thus reduced print resolution. In this paper, the mechanism of satellite droplet formation in EHD DOD printing in pulsed voltage is investigated in detail for the first time. At first, the numerical model for EHD printing is established and the correctness and credibility of the numerical results are verified experimentally. After that, the three key operating parameters peak voltage, voltage duration, and bias voltage are analyzed in detail on the formation mechanism of satellite droplets. The operating phase diagram without satellite droplets is proposed. Finally, the electric Bond number BoE and Ohnesorge number Oh are proposed for the detailed analysis of the physical parameters of the liquid on the generation of satellite droplets, and the prediction model of satellite droplet size is presented. The mechanism of satellite droplet formation in EHD printing is revealed, which provides a theoretical basis for the stable printing of satellite-free droplets and advances its application in high-resolution additive manufacturing.