SLA 3D Printer Research Articles

Introduction of the lowest printable (channel) characteristic length (LPCL) as a geometrical metric for the SLA 3D printing of embedded negative micro-structures

Introduction of the lowest printable (channel) characteristic length (LPCL) as a geometrical metric for the SLA 3D printing of embedded negative micro-structures

Dimensional Accuracy in 3D Printed Medical Models: A Follow-Up Study on SLA and SLS Technology

Background: With the rise of new 3D printers, assessing accuracy is crucial for obtaining the best results in patient care. Previous studies have shown that the highest accuracy is achieved with SLS printing technology; however, SLA printing technology has made significant improvements in recent years. Methods: In this study, a realistic anatomical model of a mandible and skull, a cutting guide for mandibular osteotomy, and a splint for orthognathic surgery were replicated five times each using two different 3D printing technologies: SLA and SLS. Results: The SLA group had a median trueness RMS value of 0.148 mm and a precision RMS value of 0.117 mm. The SLS group had a median trueness RMS value of 0.144 mm and a precision RMS value of 0.096 mm. There was no statistically significant difference in RMS values between SLS and SLA technologies regarding trueness. Regarding precision, however, the RMS values for SLS technology were significantly lower in the splint and cutting guide applications than those printed with SLA technology. Conclusions: Both 3D printing technologies produce modern models and applications with equally high dimensional accuracy. Considering current cost pressures experienced by hospitals, the lower-cost SLA 3D printer is a reliable choice for point-of-care 3D printing.

Compressive Strength Analysis of Additively Manufactured Zirconia Honeycomb Sandwich Ceramic Parts with Different Cellular Structures

In this study, ZrO2 honeycomb sandwich structures with different cellular geometry were manufactured by SLA 3D-printing technology to analyze the compressive strength behaviour. After the printing procedure, the samples were sintered at 1450 °C for 2h. Among the samples with different cellular geometry, ZrO2 parts with circular cells were superior to that of square and triangular honeycomb structures and 1867±320 MPa compressive strength was obtained for this structure. The stress distributions in honeycomb structures were investigated using the COMSOL Multiphysics® for exposing the effect of cellular geometry on compressive strength. While more uniform stress distributions were seen on the inner wall of the circular honeycomb sample, the cellular structure of the square and triangle honeycomb samples mostly displayed compressive stress concentration on the joints of the honeycomb structure. Also, according to Rankine failure criterion, the parts with square cellular geometries were found to be more prone to failure. The highest specific compressive strength was obtained for the ZrO2 parts with circular cellular geometry. These findings demonstrated that the ZrO2 honeycomb sandwich structures with circular cellular geometry produced using SLA ceramic 3D-printing technology may be a suitable material to utilize in lightweight structural designs.

Analytical model of friction at low shear rates for soft materials in 3D printing.

The biological properties of silicone elastomers such as polydimethylsiloxane (PDMS) have widespread use in biomedicine for soft tissue implants, contact lenses, soft robots, and many other small medical devices, due to its exceptional biocompatibility. Additive manufacturing of soft materials still has significant challenges even with major advancements that have occurred in development of these technologies for customized medical devices and tissue engineering. The aim of this study was to develop a mathematical model of tangential stress in relation to shear stress, shear rate, 3D printing pressure and velocity, for non-Newtonian gels and fluids that are used as materials for 3D printing. This study used FENE (finitely extensible nonlinear elastic model) model, for non-Newtonian gels and fluids to define the dependences between tangential stress, velocity, and pressure, considering viscosity, shear stress and shear rates as governing factors in soft materials friction and adhesion. Experimental samples were fabricated as showcases, by SLA and FDM 3D printing technologies: elastic polymer samples with properties resembling elastic properties of PDMS and thermoplastic polyurethane (TPU) samples. Experimental 3D printing parameters were used in the developed analytical solution to analyse the relationships between governing influential factors (tangential stress, printing pressure, printing speed, shear rate and friction coefficient). Maple software was used for numerical modelling. Analytical model applied on a printed elastic polymer, at low shear rates, exhibited numerical values of tangential stress of 0.208-0.216 N m - 2 at printing velocities of 0.9 to 1.2 mm s - 1, while the coefficient of friction was as low as 0.09-0.16. These values were in accordance with experimental data in literature. Printing pressure did not significantly influence tangential stress, whereas it was slightly influenced by shear rate changes. Friction coefficient linearly increased with tangential stress. Simple analytical model of friction for elastic polymer in SLA 3D printing showed good correspondence with experimental literature data for low shear rates, thus indicating possibility to use it for prediction of printing parameters towards desired dimensional accuracy of printed objects. Further development of this analytical model should enable other shear rate regimes, as well as additional soft materials and printing parameters.

Measuring the effects of faults for the rotational characteristics of small plastic gears

Abstract The measurement of the recirculation torque on the input side of the gearbox is a commonly used method for gear drives. This can also be suitable for detecting the effects of periodically occurring faults on small plastic gears, for example the faults of the tooth thickness or pitch. In this article, we investigate the tooth thickness faults of small plastic gears manufactured with an SLA 3D printer. In our work, we first determine the fluctuation of chordal tooth thickness by microscopic examination. Then, using a special device, we measure the same fluctuation in the recirculation torque curve. In addition, we also examine some cases where the tooth thickness is decreased or increased with a great extent.

Mechanical Behavior of 3D-Printed Thickness Gradient Honeycomb Structures.

In order to obtain a lightweight, high-strength, and customizable cellular structure to meet the needs of modern production and life, the mechanical properties of four thickness gradient honeycomb structures were studied. In this paper, four types of honeycomb structure specimens with the same porosity and different Poisson's ratios were designed and manufactured by using SLA 3D-printing technology, including the honeycomb, square honeycomb, quasi-square honeycomb, and re-entrant honeycomb structures. Based on the plane compression mechanical properties and failure mode analysis of these specimens, the thickness gradient is applied to the honeycomb structure, and four structural forms of the thickness gradient honeycomb structure are formed. The experimental results show that the thickness gradient honeycomb structure exhibits better mechanical properties than the honeycomb structure with a uniform cellular wall thickness. In the studied thickness gradient honeycomb structure, the mechanical properties of the whole structure can be significantly improved by increasing the thickness of cell walls at the upper and lower ends of the structure. The wall thickness, arrangement order, shape, and Poisson's ratio of the cell all have a significant impact on the mechanical properties of the specimens. These results provide an effective basis for the design and application of cellular structures in the future.

Masked stereolithography 3D printing of a brain tissue from an MRI data set

3D printing technology holds tremendous promise for applications in the medical field, particularly in the creation of anatomical models. The accuracy of 3D-printed anatomical models is of utmost importance, especially for surgeons engaged in complex surgical planning. The goal of this study was to create an anatomically precise model of brain tissue using data obtained from an MRI scan, with a resin-based Masked Stereolithography 3D printer, and to assess the model's potential uses. The process of creating an anatomical brain model with an SLA 3D printer was divided into six fundamental stages. The 3D printing process for this project necessitated 55.4 g of resin, and the total printing time was 4 h and 56 min. Any liquid resin residues on the brain structure eliminated through cleaning have been conducted using 99.6 % pure isopropyl alcohol. Following the printing phase, the produced model underwent a curing process in a chamber illuminated with ultraviolet light at a wavelength of 405 nm to ensure complete solidification. Once solidification is completed, the dimensions of the brain are measured with a micrometer and compared with those digitally generated from the MRI scan data. The results showed that the overall dimensional error was less than 1 %.

ОБЗОР И СРАВНЕНИЕ СОВРЕМЕННЫХ ТЕХНОЛОГИЙ ДЛЯ 3D-ПЕЧАТИ В СТОМАТОЛОГИИ И ЧЕЛЮСТНО-ЛИЦЕВОМ ПРОТЕЗИРОВАНИИ, ДОСТУПНЫХ НА ТЕРРИТОРИИ РФ

Subject. SLA and LCD 3D-printing technologies used in dentistry and maxillofacial prosthetics. Objectives. To compare and systematize SLA and LCD 3D printing devices and technologies available in the Russian Federation. To Print a prototype of the ear epithesis. Methodology. collection and analysis of available literature sources, systematization of the information received. Comparison of various 3D printers, recommendations for usage depending on the required tasks. 3D-Print of epithesis of the ear by using LCD technology. Results. SLA and LCD printing technologies are similar in a number of parameters we studied. LCD technology showed higher printing speed compared to SLA technology. At the same time, the accuracy of the product for all SLA printers turned out to be higher in comparison with the most accurate LCD technology printer. The cost of SLA printers is on average higher than LCD printers. The prototype of the epithesis of the auricle can be reproduced using LCD technology. Conclusion. Photopolymer 3D printers with SLA technology produce more detailed and sharper end products than LCD printers. Photopolymer 3D printers with SLA technology are slower than LCD technology. SLA and LCD technologies are quite close in certain parameters. LCD technology can be used at the stages of rehabilitation of patients with ear defects.

DESIGN AND PRINTING OF HELICAL GEAR WITH RESIN 3D PRINTING MACHINE

Stereolithography 3D printing (SLA) has evolved into a leading additive manufacturing technology, revolutionizing various industries with its precision and versatility. This paper provides a comprehensive overview of the advances and challenges in SLA 3D printing technology. This overview begins with an overview of the principles of SLA printing, including the photopolymerization process and the role of digital slicing software in creating printable 3D models. Next, recent advances in materials such as photopolymer resins have improved mechanical, biocompatibility, and functional properties, expanding the applications of his SLA printing in areas such as aerospace, healthcare, and consumer products. This section explains. Additionally, this review addresses improvements to hardware components such as light sources, build platforms, and optical systems, resulting in increased print speed, resolution, and reliability. Additionally, the impact of advances in post-processing techniques such as UV curing, rinsing, and surface finishing on the final print quality will be investigated. Key Words: Stereolithography, photopolymerization, 3D printing, hardware, UV curing, rinsing.

Suitability of novel 3D-printed and coated vessels for water calorimetry.

In water calorimetry, absolute dose to water is determined by measuring radiation-induced temperature rises. In conventional water calorimeters, temperature detectors are housed in handmade glass vessels that are filled with high-purity water, thus mitigating radiation-induced exo/endothermic chemical reactions of impurities that would otherwise introduce additional heat gain/loss, known as heat defect. Being hand-crafted, these glass vessels may suffer from imperfections, have shape and design constraints, are often backordered, and can be prohibitively expensive. The purpose of this work is to determine suitability of 3D-printed plastic vessels that are further coated for use in water calorimetry applications, and to study their stability and characterize their associated heat defect correction factor ( . This novel vessel production technique would allow for cost-effective rapid construction of vessels that can be produced with high accuracy and designs that are simply not practical with current glass vessel construction techniques. This in turn enables water calorimetry applications in many novel radiation delivery modalities, which may include spherical vessels in GammaKnife ICON water calorimetry as an example. Eight vessels were 3D-printed using Accura ClearVue in an SLA 3D-printer. Two vessels were coated with Parylene C and four were coated with Parylene N. The water calorimetry preparation procedures followed for these vessels was identical to that of our traditional glass-vessels (i.e., same cleaning procedures, same high purity water, and same saturation procedures with high purity hydrogen gas). The performance of each vessel was characterized using our in-house built water calorimeter in an Elekta Versa using both 6MV flattening filter-free (FFF) and 18MV beams. The stability of the coating as function of time and accumulated dose was evaluated through repeated measurements. of each vessel was determined through cross-comparisons against an Exradin A1SL ionization chamber with direction calibration link to Canada's primary standard laboratory. of the two uncoated vessels differed by 2.8% under a 6MV FFF beam. Vessels coated with Parylenes resulted in a stable and reproducible heat defect for both energies. An overall of 1.001±0.010 and 1.005±0.010 were obtained for Parylene N and Parylene C coated vessels respectively. All Parylene coated vessels showed agreement, within the established uncertainties, to the zero-heat defect observed in a hydrogen-saturated glass vessel system. An additional long-term study (17 days) of a Parylene N vessel showed no change in response with accumulated dose and time. Electron microscopy images of a Parylene N coated vessel showed a uniform intact coating after repeated irradiations. An uncoated 3D-printed vessel is not viable for water calorimetry because it exhibits an unstable vessel-dependent heat defect. However, applying a Parylene coating stabilizes the heat defect, suggesting that coated 3D-printed vessels may be suitable for use in water calorimetry. This method facilitates the creation of intricate vessel shapes, which can be efficiently manufactured using 3D printing.

Assessment of mechanical performance of Al2O3 ceramic honeycomb sandwich structures produced with SLA 3D-printing regarding unpolymerized slurry removal strategy

Al2O3 ceramic honeycomb sandwich bars with a hexagonal core were manufactured through SLA 3D-printing to analyze the impact of hole placement, designed for the removal of uncured slurry, on the bending strength of the samples. Several holes were placed specifically on the samples in the design in two different ways. In the initial design, the holes were placed on the honeycomb sandwich structure’s upper and lower face-sheets. In the second design, the holes were positioned in the direction of the sample thickness, in the lateral walls. The moment of inertia values for the honeycomb structures were calculated with the help of experimental elastic modulus results, and true bending strength was determined according to these results. Nominal strength values were found using the common three-point bending formula. The true bending strength value of Al2O3 with lateral holes was 73% higher than Al2O3 with holes on face-sheets, while the nominal bending strength was 79% higher. Al2O3 samples with holes on face-sheets exhibited a significantly higher failure index compared with both the bulk samples and the Al2O3 samples with lateral holes. The holes on the face-sheets reduced the cross-sectional area of the tensile surface and contributed to an increase in stresses due to the stress concentration effect. The Al2O3 samples with lateral holes provided a great advantage of specific strength, reaching an average value of 65% above the specific strength of the bulk samples.

3D printing of PEGDA/bioceramic for guiding cell adhesion and migration

The adhesion and migration characteristics of osteocytes on the surface of bone materials are crucial for bone tissue regeneration, which is conducive to the directional repair of bone defects. Herein, the adhesion and migration characteristics of MC3T3-E1 cells on the surface of SLA-3D printed PEGDA/bioceramic materials were analyzed in detail. The results indicated that, in comparison to the cured PEGDA matrix, the pseudopods of cells preferred to adhere to ceramic particles, demonstrating the characteristics of hard drive migration. Furthermore, on a wavy surface with a surface roughness (Ra=2 μm) fabricated by the laser of the SLA-3D printer, MC3T3-E1 cells could grow directionally along the rough channel via contact guidance. Therefore, by controlling the distribution of ceramic particles and adjusting the surface morphology of the printed PEGDA/bioceramic materials, the migration direction of cells can be dominated, which is of great significance for the targeted repair of bone tissue.

Experimental and numerical investigation of the elliptical cyclone separator manufactured by 3D printing

Whether the cyclone separators have a high-efficient body shape is a problem that has been ignored for a long time. A series of cyclones with elliptical bodies were designed and manufactured by SLA 3D-printing. The separation performance and flow field of the cyclones were investigated using the experimental and CFD methods, respectively. The detailed flow features, such as streamlines, pressure and velocity profile distribution, and special flow phenomena of the circumferential acceleration/deceleration of the swirling gas, are analyzed. The experimental results reveal that the elliptical cyclones with a/b = 1.2 and 0.83 have about 2% increment of separation efficiency and 43% reduction of pressure drop, as well as satisfactory robustness to the particle properties and operating conditions. The circumferential acceleration/deceleration of the swirling gas creates an additional inertial force for the particles, thereby improving the elliptical cyclones' performance. The results provide innovation ideas for designing and manufacturing the better-performance cyclones.

Photopolymerization of Limonene Dioxide and Vegetable Oils as Biobased 3D-Printing Stereolithographic Formulation.

Epoxidized vegetable oils and limonene dioxide, a bis-epoxide derived from the terpene limonene, are photo-copolymerized to yield highly crosslinked networks with high conversion of all epoxide groups at ambient temperature. However, the slow polymerization of such biobased formulation polymerizes is not compatible for a use in a commercial SLA 3D printer. Adding an acrylated epoxidized vegetable oil to the bis-epoxide leads to a decrease of curing time and an increase in LDO conversion to polymer. For example, in a 60:40 wt:wt mixture of LDO and epoxidized soybean oil, the conversions of both exocyclic and endocyclic epoxide groups of LDO are ≥95%. These formulations were successfully used in SLA 3D printers, leading to generation of hard and dry complex objects using biobased formulations.

Biomechanical and Biological Properties of Stereolithography-Based 3D-Printed Zirconia Interference Screws for Anterior Cruciate Ligament Reconstruction

For effective anterior cruciate ligament (ACL) reconstruction, an interference screw (IFS) is employed to force transplantation of the ligament into the bone tunnel. In this study, IFSs were successfully designed and prepared, and the top tooth width, thread depth, and drive structure were parameterized with a forming accuracy of 80.0 ± 21.1 µm using SLA–3D printing technology. To improve the initial stability of ACL reconstruction, a biomechanical model was established, and the results were optimized through insertion torque and tensile testing. Consequently, the IFS with the top tooth width of 0.4 mm, thread depth of 0.8 mm, and hexagon drive, matching with the Φ8 mm bone tunnel, exhibits the best mechanical properties (maximum insertion torque of 1.064 ± 0.117 N m, ultimate load of 446.126 ± 37.632 N, stiffness of 66.33 ± 27.48 N/mm). Additionally, the ZrO2/PDA/RGD/Zn2+ bioactive coating was found to significantly improve the surface bioactivity of zirconia IFS. In conclusion, this study has significant implications for ACL reconstruction.

Rapid prototyping of a modular optical flow cell for image-based droplet size measurements in emulsification processes

Emulsification processes are often found in the process industry and their evaluation is crucial for product quality and safety. Numerous methods exist to analyze critical quality attributes (CQA) such as the droplet sizes and droplet size distribution (DSD) of an emulsification process. During the emulsification process, the optical process accessibility may be limited due to high disperse phase content of liquid-liquid systems. To overcome this challenge, a modular, optical measurement flow cell is presented to widen the application window of optical methods in emulsification processes. In this contribution, the channel geometry is subject of optimization to modify the flow characteristics and produce high optical quality. In terms of rapid prototyping, an iterative optimization procedure via SLA-3D printing was used to increase operability. The results demonstrated that the flow cell resulting from the optimization procedure provides a broad observation window for droplet detection.Graphical abstract

Ultimate flexural strength and Young’s modulus analysis of denture base resins for masked stereolithography 3D printing technology

of the study is to investigate the ultimate flexural strength and Young’s modulus of some materials, which can be used for complete denture fabrication by Masked stereolithography 3D printing technology.Three groups of five specimens each were fabricated. Two of the groups are 3D printed by Masked SLA 3D printer of two commonly used denture base resins. The third group is set to be a control as the specimens were fabricated of a heat-curing acrylic resin. A three-point flexural test tested the objects, and the data collected was used to determine ultimate flexural strength and Young’s modulus calculation. All the results are compared to the ISO Standard 20795-1.The data shows that the mean ultimate flexural strength of the 3D printed specimens is 87 MPa - 89 MPa. Their results are very similar to those for the heat-curing acrylic resin, which means the ultimate flexural strength is 93 MPa. The mean Young’s modulus obtained for the first group of 3D printed specimens is 2263.21 MPa and 2377.44 MPa for the second one. As for the control group, 2396.06 MPa is achieved. When ISO Standard 20795-1 is inspected, all the data obtained covers the minimum requirements.The limitations of the study concern to some additional factors that should be observed for more detailed evaluation. For example, the level of the final polymerization of light-curing resins for 3D printing, their ability to washstand to different defect and denture-bearing area characteristics (the notch for the labial and buccal frenulum, chambers for torus release, etc.), the ability of the materials to withstand to cyclic load, etc.3D printing is faster and cheaper than conventional methods for complete denture fabrication. The knowledge about the mechanical properties of the different materials for 3D printing is very valuable for properly selecting a material and approach for complete denture fabrication.Nowadays, 3D printing is essential in dentistry. For this reason, observation and knowledge of the raw materials properties is very important for the proper choice of a material and/or technology for each clinical case.

Branched Silicone Acrylates Enhanced Photocurable Epoxy Resins with High Strength, Toughness, and Low Dielectric Constant for SLA 3D Printing

Branched Silicone Acrylates Enhanced Photocurable Epoxy Resins with High Strength, Toughness, and Low Dielectric Constant for SLA 3D Printing

PresTo: A liquid-filled camera for low-cost imaging in the deep sea

Deep-sea imaging systems are traditionally expensive to manufacture and are physically scaled depending on the operating depth of their housing and the internal camera/lens components. Liquid and epoxy filled instrument designs are increasing in popularity as a way to reduce the cost and size of deep-sea housings. Recent advances in 3D printing have facilitated rapid prototyping of these pressure tolerant deep-sea designs. This study presents the design of PresTo, a liquid-filled pressure tolerant camera manufactured using SLA 3D printing methods. This is a compact and low-cost imaging system filled with deionized water and coated in epoxy to remove all implodable air volumes in the camera. The lens design for PresTo can be easily customized to any focal length and with zoom capabilities using a magnetically driven focus mechanism. Images taken with PresTo likely have minimal image distortions compared to other underwater cameras with flat viewports because, due to the elimination of a flat viewport solely for the reason of pressure isolation, there is an inherent reduction in the refractive indices of the surrounding environment and internal medium. The presented system has been field-tested to depths exceeding 1700 m and has been hydrostatically tested to function beyond 2600 m.

Polyelectrolyte Multilayer Coating on 3D Printed PEGDA/TCP Scaffold with Improved Cell Proliferation

Bioactive coating of ceramic scaffolds is an effective way to ameliorate osseointegration and attenuate implant-induced inflammatory responses, which should be biocompatible and possess suitable mechanical properties to regulate cell adhesion and migration. In this study, a poly (ethylene glycol) diacrylate/tricalcium phosphate (PEGDA/TCP) ceramic scaffold was prepared using SLA-3D printing, and its compressive strength was 8.9 ± 1.0 MPa. Chitosan (Chi) and chondroitin sulfate (CS) were assembled on the surface of the PEGDA/TCP scaffolds and crosslinked with 1-ethyl-3-(3-dimethylaminopropyl) -carbodiimide/ N-hydroxysuccinimide (EDC/NHS). Scanning electron microscope (SEM), Fourier transform infrared (FTIR), and laser scanning microscope were used to evaluate the surface modification of the PEGDA/TCP scaffolds. Cellular tests showed that polyelectrolyte multilayers (PEMs) promoted cell adhesion and proliferation of osteoblasts relative to unmodified scaffolds. Furthermore, it can be demonstrated that the SLA-3D printed TCP scaffolds could meet the compressive requirements of trabecular bones, and the bioactivity of the bone scaffolds could be effectively improved by combining them with Chi/CS PEM.