Printing Accuracy Research Articles

Impact of internal design on the accuracy of 3-dimensionally printed casts fabricated by stereolithography and digital light processing technology

Statement of problemAltering the internal design of 3-dimensionally (3D) printed dental casts may help to reduce material and time consumption. However, it remains unclear whether such changes would compromise the accuracy of the casts. Further research is also needed to determine the optimal internal design that would maximize printing accuracy. PurposeThe purpose of this in vitro study was to evaluate the impact of internal design on the accuracy (trueness and precision) of 3D printed dental casts fabricated by stereolithography (SLA) and digital light processing (DLP) technology. Material and methodsA reference digital cast was obtained by scanning a maxillary typodont with an intraoral scanner to create 4 types of internal designs, including hollow interior with perforated base (HWB), hollow interior without base (HB), all solid (S), and internal support structure with perforated base (SWB). Digital casts with different internal designs were printed by two 3D printers with different technologies (SLA and DLP). The printed casts were scanned by a desktop scanner to obtain standard tessellation language (STL) format research digital casts. All reference and research digital casts were imported into a software program for comparison and analysis of accuracy. Differences between the reference and research digital casts were quantitatively indicated by the root mean square (RMS) value. The Kruskal-Wallis 1-way ANOVA was used to test significant differences between the different internal design types and the Mann-Whitney U test was used to test significant differences between the two 3D printers (α=.05). ResultsThe Kruskal-Wallis 1-way ANOVA revealed significant differences in the trueness and precision of different internal design types (all P<.001) for casts printed by both 3D printers. The trueness and precision were significantly worse for the HB design than for the other design types for casts printed by both 3D printers (all P<.05). Regardless of the design type, the trueness was significantly better for casts printed by the SLA-based printer than for casts printed by the DLP-based printer (all P<.05). The precision was significantly worse for casts printed by the SLA-based printer than for casts printed by the DLP-based printer (all P<.05). ConclusionsThe internal design may affect the accuracy of 3D printing. The base is necessary to ensure the accuracy of 3D printed dental casts, whereas the internal support structure did not affect the accuracy of 3D printed dental casts. An all-solid design led to higher precision, but not higher trueness. Dental casts printed with SLA technology have higher trueness and lower precision than those printed with DLP technology.

Direct Ink Writing of Alginate–Gelatin Hydrogel: An Optimization of Ink Property Design and Printing Process Efficacy

Direct Ink Writing (DIW), which is widely used for developing functional 3D scaffolds that have robust structural integrity for the growth of target tissues/cells, has emerged as an appealing method for biomedical applications. The production of 3D structures involves three separate but interconnected stages (material development, printing process, and post-printing treatment), whose effectiveness is influenced by several factors that therefore make it challenging to optimize the entire procedure. By studying the material processability and leveling the printing settings, this study proposes a three-step method to enhance the ink property design and the printer’s performance. The recommended approach is focused on the thorough study of alginate–gelatin hydrogel properties, which is a commonly used ink in biomedical applications, due to its natural origin through marine flora, as well as the development process parameters and their intercorrelations. Principal Component Analysis in comparison with K-means clustering was applied to reveal material properties that are highly correlated with additive manufacturing (AM) processability, and Taguchi’s Design of Experiments (DOE) determined the printing settings (primary and secondary) for achieving optimum printing accuracy. PCA results were affirmed by K-means clustering and showed that viscosity, m, G′ and G″ govern blends’ printing behavior while application of DOE led to 85% pore area printability.

3D printable vegan plant-based meat analogue: Fortification with three different mushrooms, investigation of printability, and characterization

In this study, a meat analogue formulation prepared using different protein sources as a printable ink for 3D printers and fortified with three different mushroom cultivars (reishi, Ganoderma lucidum (GL); saffron milk-cap, Lactarius deliciosus (LD); and oyster, Pleurotus ostreatus (PO)). 3D printing performance of the prepared inks was evaluated by factorial design in terms of nozzle height, printing speed, and flow compensation. New methods of maximum layer height and reprintability of plant-based meat analogues were conducted for the first time. Inks were characterized by analyzing rheological properties, microstructure, color characteristics, texture profile, cooking loss, amino acid content, and sensory evaluation. Results showed that the nozzle height and printing speed were found to be most effective on accuracy of prints and smoothness of layers. All inks (C, GL, LD and PO) represented shear-thinning and gel-like viscoelastic behavior (G′ > G″) with predominant elasticity (tan δ < 1). Therefore they were suited for 3D printing and possessed supporting the following layers for additive manufacturing as well as meeting the criteria for a stable structure. Meat analogue was printed successfully without perceived defects in all formulations, except the GL was looking linty. LD and PO inks brought the advantage of recycling as a result of their re-printability whereas GL could not. Moreover, mushroom fortification reduced hardness, stiffness, springiness, and chewiness properties of the meat analogues whereas it increased the juiciness with reasonable overall acceptance. Mushroom fortification also enhanced the nutritional value and improved release of umami amino acids. The findings of the study demonstrated that mushrooms could be a functional and nutritious candidate for 3D printable plant-based meat analogues.

3D-Printed Bioceramic Scaffolds with High Strength and High Precision

Due to the increasing cases of bone damage and bone graft demand, bone-repair technology has great social and economic benefits and the manufacturing of artificial bone implants has become a focus in the domain of regenerative therapy. Considering that the traditional manufacturing process cannot effectively control the overall size of the scaffold, the diameter and shape of micropores, and the interoperability of micropores, 3D printing technology has emerged as a focal point of research within the realm of bone tissue engineering. However, the printing accuracy of extrusion-based biological 3D printing techniques is low. In this research, we utilized three-dimensional printing technology to develop high-precision magnesium-containing silicate (CSi-Mg) scaffolds. The precision of this innovative method was scrutinized and the influence of pore size on scaffold strength was systematically analyzed. Furthermore, the influence of the pore architecture on the sidewalls of these 3D-printed scaffolds was evaluated in terms of mechanical properties. The CSi-Mg scaffold, post a 3-week immersion in a simulated body of fluid, demonstrated a high modulus of elasticity (exceeding 404 MPa) and significant compressive strength (beyond 47 MPa). Furthermore, it exhibited commendable bioactivity and biodegradability. These results suggest that the high-precision 3D-printed CSi-Mg scaffolds hold great promise for addressing challenging bone defect cases.

Study on the structure and preservation mechanism of 3D-Printed surimi with Ca2+ and Xylo-oligosaccharides

The viscosity and plasticity of surimi is remarkable, which is a suitable 3D printing material. But low printing accuracy limit its wide application. Adding xylo-oligosaccharide (XOS) can enhance printing accuracy of surimi printing ink and improve the self-supporting ability and anti-deformation ability of the printed object. At the same time, XOS can impart antioxidant properties to 3D printed surimi. Additionally, adding 20 mM kg−1 of Ca2+ to the surimi can significantly improve the printing accuracy. With the addition of Ca2+, the gel strength and texture of surimi are enhanced, as well as the surimi protein became denser. Moreover, the Ca2+ in the “ink” can activate the activity of digestive enzymes which increase the contact of enzymes and surimi. The process of enzymatic hydrolysis is promoted, which improving the release rate and antioxidant properties of XOS. Functional surimi with Ca2+ can be used to deliver functional components and enhance the printing effects.

Hot melt extrusion with low-temperature deposition-coupling control improves the 3D printing accuracy of gelatin/fish pulp recombinant products

The flow properties of original materials directly affect the shape customization of 3D printing. In order to improve the molding quality, the 3D printing equipment was developed, which was characterized by a variable pressure and temperature extrusion unit, a numerical control transmission unit, an extrusion refrigeration unit, and a control box. The optimal pretreatment condition of sturgeon skin was 0.015 M phosphoric acid with higher gel strength (739.27 g), which could be a good substitute for commercial gelatin. The 7% gelatin/fish pulp reconstituted system could exhibit optimum printing properties through an improved 3D printer. The reconstituted system displayed a smoother printing process and superior accuracy during the process of 3D printing, and showed higher apparent viscosity and modulus during the process of cooling and molding. Additionally, the network structure of 3D printing products of reconstituted the gelatin/fish pulp was denser, which showed higher water holding capacity (89.03%), higher hardness (775.64 g), and constant elasticity (0.9853).

LESSONS LEARNT ON 3D PRINTING MICHELANGELO’S DAVID REPLICA

Abstract. This paper reports and discusses the results of some experimental investigations carried out with the aim to identify the best conditions for a safe exposure of the 3D printed large-scale replica of Michelangelo’s David during its exhibition in the Italian Pavilion of the Expo 2020 Dubai.The whole project posed numerous challenges due to the dimension of the Michelangelo’s David (which is over seven metres high and weighs more than five ton). As a matter of fact, on the one hand, no standardized procedures have been still established to define accuracy and quality of 3D printing. On the other hand, the large-scale printing opens up new issues concerning the mechanical properties requested of the printing material and the printing set-up that is necessary to ensure the stability and durability of the printed replica.After a general picture of the whole project, thermal characterization of the material used to print the replica and mechanical tests of samples obtained form the replica are reported and discussed. Thermal characterisation showed that the stiffness of the material was strongly influenced by temperature and that it decreased continuously as this parameter increased. Mechanical tests showed a brittle behaviour, with a collapse load approximately 10 times higher than the internal loads resulting from the self-weight alone.The analyses here presented constitute some of the groundwork carried out for the realisation and installation of the 3D printed replica of Michelangelo’s David. This conceptualisation, considering both the extreme environmental conditions and the large-size of the replica, has been particularly challenging and the adopted procedure was useful to verify the different phases of the realisation of the replica.

Effect of oil content and protein particles concentration on non-dairy whip topping based on Pickering emulsion system and their 3D printing properties

Non-dairy whip topping is a typical food emulsion system that is popular among consumers. In this study, a novel non-dairy whip topping without hydrogenated vegetable oil was fabricated based on Pickering emulsion system. The results of particle size and stability of the pre-whipping emulsion showed that the initial emulsion particle size increased to 472.00 ± 1.73 nm as the oil content increased to 30%, and the particle size of the aged emulsion increased to 974.00 ± 9.54 nm,and the stability decreased. The particle size tended to decrease and stability gradually increased with increasing protein particles concentration. Based on the observation of bubbles in the cream system after whipping, it was found that the increase of oil content and protein particles concentration was helpful to the cream structure. Furthermore, the results of rheological and textural properties showed that all the creams presented shear thinning characteristics, and with the increase of oil content and protein particles concentration, the viscosity and energy storage modulus (G′) increased, indicating good printability. Additionally, the 3D printing of the creams displayed that the viscosity was too large to reduce the accuracy of printing, while the accuracy and stability of the printed shapes reached 99.27% and 99.72% at 25% oil content and 1.6% protein particles concentration, respectively. This study will be important for Pickering emulsion system to solve health problems in food and expand food 3D printing applications.

Curing performance and print accuracy of oxidized SiC ceramic via vat photopolymerization

To improve the print quality of SiC ceramic, an amorphous SiO2 layer is prepared on the surface of SiC by oxidation (SiC@SiO2). The changes in curing depth and width direction of SiC@SiO2 curing sheets with different degrees of oxidation were investigated. The results showed that curing depth increased while curing width decreased with an increasing degree of oxidation. The edge morphologies of SiC@SiO2 curing sheets changed from serration to flat shape with increasing degree of oxidation, and uneven overcuring regions appear in the width direction. Additionally, 12% SiC@SiO2 ceramic was fabricated via vat photopolymerization combined with reaction sintering. The dimensional deviation ratio of printed green bodies increased with decreasing printed line width and pore diameter. The minimum printed line width of 329 μm and pore diameter of 483 μm with good print quality were obtained. Furthermore, the flexural strength of 225.4 MPa and bulk density of 2.77 g cm−3 for sintered 12% SiC@SiO2 parts were obtained.

3D printed twin block: A feasibility study

AimsTwin blocks are appliances used for Class II skeletal discrepancies, where the lower jaw is positioned more posteriorly compared to the upper. The conventional method of fabrication of this appliance is tedious and labour-intensive; hence this study intends to explore the feasibility of a digital workflow to three-dimensionally (3D) print them. MethodsThree sets of twin blocks, identical except for amount of offset (0.0 mm, 0.1 mm and 0.2 mm), were designed and 3D printed for 5 anonymized scans of patients with Class II skeletal discrepancies. The intaglio surfaces of the 0.0 mm offset twin blocks were scanned and superimposed onto their original computer-aided-design files. The resultant colour maps, root mean square (RMS) deviations, and percentage in-tolerance values at thresholds of 0.1 mm and 0.2 mm were assessed. The fit and retention of all twin blocks were assessed on their 3D printed models via a fit and retention score (FRS). ResultsThe median RMS deviation was 0.10 mm; percentage in-tolerance values at thresholds of 0.1 mm and 0.2 mm were 79.90%, and 94.51%. Printing deviations occurred most often at labial and incisal edges anteriorly, and buccal and occlusal surfaces posteriorly. There was no significant difference between the total FRS for the three groups (p = 0.076). However, the frequency of satisfactory scores for upper fit (p = 0.049), lower fit (p = 0.018), upper retention (p = 0.038) and lower retention (p = 0.015) differed significantly between the three groups. ConclusionThis study demonstrated the viability of a digital workflow to 3D print twin blocks. Print accuracy was satisfactory, with 0.1 mm offset providing the best fit and retention.

Designable thermal conductivity and mechanical property of polydimethylsiloxane-based composite prepared by thermoset 3D printing

Three-dimensional (3D) printing is a layered additive manufacturing technology. In common 3D printing methods, direct ink writing (DIW) and fused deposition modeling (FDM) are new extrusion-based technologies. FDM works by melting a hot-melt material and squeezing it out through a tiny nozzle. Conversely, DIW, accurately deposit accurate amount of paste at different distances through the conveying system (extruder). As a unique approach, this technology introduces design freedom, versatility and stability into the printing structure at the same time. In addition, DIW technology is suitable for thermoset 3D printing. The influences of filler orientation in polymer matrix and printing paths on the thermal conductivity (λ) of thermoset 3D printing products are worth studying. Therefore, we built a thermoset 3D printer, and optimized the structure of the nozzle device, effectively improved the printing accuracy. Polydimethylsiloxane (PDMS) and hexagonal boron nitride (hBN) are selected as polymer matrix and thermally conductive filler, respectively. Compared with pure PDMS, the λ value of hBN/PDMS composites increases obviously with increasing hBN content. Meanwhile, the mechanical properties of composites with different printing paths are systematically studied. This designable orientation provides opportunities and challenges for other functional structure design such as hollow structure.

Research on Properties of Silicone-Modified Epoxy Resin and 3D Printing Materials.

A kind of organosilicon intermediate was prepared using isophorone diisocyanate (IPDI), hydroxyl silicone oil (HSO), and hydroxyethyl acrylate (HEA). The organosilicon modification of epoxy resin was realized by introducing a -Si-O- group into the side chain of epoxy resin by chemical grafting. The effects of organosilicon modification of epoxy resin on the mechanical properties systematically discuss its heat resistance and micromorphology. The results indicate that the curing shrinkage of the resin was decreased and the printing accuracy was improved. At the same time, the mechanical properties of the material are enhanced; the IS and elongation at break (EAB) are enhanced by 32.8 and 8.65%, respectively. The brittle fracture is changed to a ductile fracture, and the tensile strength (TS) of the material is decreased. The glass transition temperature (GTT) of the modified epoxy resin increased by 8.46 °C, and T50% and Tmax increased by 1.9 and 6 °C, respectively, indicating that the heat resistance of the modified epoxy resin was improved.

RESEARCH INTO THE ACCURACY OF HOLES IN 3D PRINTING USING TAGUCHI METHOD

The article discusses the impact of two factors on the accuracy of the hole sizes - print speed and layer thickness in 3D printing. Nine samples of the ABS polymer were printed by using a 3D printer, then the impact of both of the factors on the accuracy of 3D printing of the holes was evaluated. Taguchi's method was applied with the help of DOE in Minitab to evaluate the impact of the two factors.

Effect of Ca2+ on 3D printing accuracy and antioxidant efficacy of nano starch-lutein surimi: mechanical properties, chemical bonds and release rate.

Nano starch-lutein (NS-L) can be used in 3D printed functional surimi. However, the lutein release and printing effect are not ideal. The purpose of this study was to facilitate the function and printing properties of surimi by adding the combination of Ca2+ and NS-L. Printing properties, lutein release and anti-oxidation of printed Ca2+ -NS-L-surimi were determined. The NS-L-surimi with 20 mM·kg-1 Ca2+ had the best printing effects (fine accuracy, 99 ± 1%). Compared to NS-L-surimi, the structure became denser after adding Ca2+ , the gel strength, hardness, elasticity, yield stress (τ), water holding capacity of Ca2+ -NS-L-surimi increased by about 17 ± 4%, 3 ± 1%, 9 ± 2%, 20 ± 4%, 40 ± 5% respectively. These enhanced mechanical strength and self-supporting ability to resist binding deformation and improve printing accuracy. Moreover, salt dissolution and increased hydrophobic force by Ca2+ stimulated protein stretching and aggregation, leading to enhancement of gel formation. Decreased printing effects of NS-L-surimi with excessive Ca2+ (> 20 mM·kg-1 ) caused by excessive gel strength and τ, leading to strong extrusion force and low extrudability. Additionally, Ca2+ -NS-L-surimi had higher digestibility and lutein release rate (increased from 55 ± 2% to 73 ± 3%), because Ca2+ made NS-L-surimi structure porous, which promoted contact of enzyme-protein. Furthermore, weakened ionic bonds reduced electron binding bondage that combined with released lutein to provide more electrons for enhancing anti-oxidation. Collectively, 20 mM·kg-1 Ca2+ could better promote printing process and function exertion of NS-L-surimi, facilitating the application of 3D printed functional surimi. This article is protected by copyright. All rights reserved.

Use of compression test to determine the Young's modulus of the titanium alloy Ti6Al4V manufactured via direct metal laser sintering

AbstractThe research is dedicated to determine one of the most important mechanical properties which is the Young's modulus. Its value is crucial for clearly explaining and understanding the results of any mechanical loading experiment. Three cylindrical samples of 15 mm height and 7.5 mm diameter were designed using SpaceClaim application in the ANSYS Software and then 3D printed using Direct Metal Laser Sintering via EOS M 290 3D printer. The specimens were then tested under compression in order to determine the value of the Young's modulus for titanium alloy of grade 23 (Ti, Al, V, O, N, C, H, Fe, Y). The finite element method was executed using ANSYS mechanical to run a comparison between laboratory results with nominal results of the Young's modulus. Young's modulus value is affected by the 3D printing accuracy and quality, the material's quality as well; however, the deviation is within 10%.

Effects of pressure and height on printability for soft materials

Extrusion-based printing with soft materials is an additive manufacturing technology, which is widely used in biomedical fields such as skin reconstruction, muscle repair, and cartilage regeneration, etc. Constructing high-precision printed structures and maintaining high cellular bioactivity are key issues in the in vitro construction of tissues and organs using extrusion bioprinting. There are some printing paraments such as pressure, height, nozzle type (eg, length and inner diameter), translational speed, etc. can have a huge influence on the structural fidelity. In this work, we put forward a quantitative test method to evaluate the printing accuracy is influenced by pressure and height. The results show that higher pressure can benefit uniformity (the filament width is equal everywhere), and higher height leads to higher uniformity only in low pressure for paste. This study can provide researchers with the tunning suggestions of printing paraments, which may promote the development of printing accuracy in the future.

Rheological properties, gel properties and 3D printing performance of soy protein isolate gel inks added with different types of apricot polysaccharides

A soybean protein isolate (SPI)-apricot polysaccharide gel with hypolipidemic activity that can be used for 3D printing was prepared and the mechanism of its gel formation was studied in this work. The results demonstrated that adding apricot polysaccharide to SPI could effectively improve the bound water content, viscoelastic properties and rheological properties of the gels. Low-field NMR, FT-IR spectroscopy and surface hydrophobicity confirmed that the interactions between SPI and apricot polysaccharide were mainly realized by electrostatic interactions, hydrophobic and hydrogen bonding. Furthermore, adding modified polysaccharide treated by ultrasonic-assisted Fenton method to SPI on the basis of low-concentration apricot polysaccharide contributed to improving the 3D printing accuracy and stability of the gel. Consequently, the gel formed by adding apricot polysaccharide (0.5 %, m/v) and modified polysaccharide (0.1 %, m/v) to SPI had the best hypolipidemic activity (the binding rate of sodium taurocholate and sodium glycocholate were 75.33 % and 72.86 %, respectively) and 3D printing characteristics.

Machine learning boosts three-dimensional bioprinting.

Three-dimensional (3D) bioprinting is a computer-controlled technology that combines biological factors and bioinks to print an accurate 3D structure in a layer- by-layer fashion. 3D bioprinting is a new tissue engineering technology based on rapid prototyping and additive manufacturing technology, combined with various disciplines. In addition to the problems in in vitro culture process, the bioprinting procedure is also afflicted with a few issues: (1) difficulty in looking for the appropriate bioink to match the printing parameters to reduce cell damage and mortality; and (2) difficulty in improving the printing accuracy in the printing process. Data- driven machine learning algorithms with powerful predictive capabilities have natural advantages in behavior prediction and new model exploration. Combining machine learning algorithms with 3D bioprinting helps to find more efficient bioinks, determine printing parameters, and detect defects in the printing process. This paper introduces several machine learning algorithms in detail, summarizes the role of machine learning in additive manufacturing applications, and reviews the research progress of the combination of 3D bioprinting and machine learning in recent years, especially the improvement of bioink generation, the optimization of printing parameter, and the detection of printing defect.

Steering Potential for Printing Highly Aligned Discontinuous Fibre Composite Filament.

DcAFF (discontinuous aligned fibre filament) is a novel material for fused filament fabrication (FFF) 3D printing made of highly aligned discontinuous fibres produced using high performance discontinuous fibre (HiPerDiF) technology. It reinforces a thermoplastic matrix to provide high mechanical performance and formability. Accurate printing of DcAFF poses a challenge, especially for complex geometries, because: (i) there is a discrepancy between the path where the filament experiences the adhering pressure from the filleted nozzle and the nozzle path; and (ii) the rasters display poor adhesion to the build platform immediately after deposition, which causes the filament to be dragged when the printing direction changes. This paper explains the implication of these phenomena on steering capabilities and examines the techniques for improving DcAFF printing accuracy. In the first approach, the machine parameters were adjusted to improve the quality of the sharp turning angle without changing the desired path, but this showed insignificant effects in terms of precision improvements. In the second approach, a printing path modification with a compensation algorithm was introduced. The nature of the inaccuracy of the printing at the turning point was studied with a first-order lag relationship. Then the equation to describe the deposition raster inaccuracy was determined. A proportional-integral (PI) controller was added to the equation to calculate the nozzle movement in order to bring the raster back to the desired path. The applied compensation path is shown to give an accuracy improvement in curvilinear printing paths. This is particularly beneficial when printing larger circular diameter curvilinear printed parts. The developed printing approach can be applied with other fibre reinforced filaments to achieve complex geometries.

Application of lignocellulosic composite (Taiwan incense-cedar) for digital light processing (DLP) in 3D printing

ABSTRACT Adding wood fiber to the 3D printing material can make the 3D-printed product have the characteristics of natural dyeing and material. Because wood fiber is mostly waste and cheap, it can reduce material cost. For environmental sustainability, it is a very promising filling material. Currently, there are 3D printing consumables using wood fiber on the market, most of which are made by drawing wires with polylactic acid (PLA). Due to the low accuracy and yield of frequency-division multiplexing (FDM) printing using filaments, it cannot be extended to mass production industrial use, and natural pellets cause the problem of nozzle clogging. In contrast, if fiber is mixed with polyurethane acrylate (PUA), it can be printed by DLP and cured through the photocuring reaction. This method has no clogging problem and has high printing accuracy, enabling industrialized mass production that requires high yield and accuracy. Therefore, in this study, Taiwan incense-cedar (high economic and ecological value tree species) was applied to commercial PUA materials for DLP 3D printing. Mix wood fiber with different ratios and commercial PUA, conduct printing and performance tests, and then compare the mechanical properties and finished product effects with commercial PLA printed products that add wood fiber.