Tolerance Control Using Subvoxel Gray-Scale DLP 3D Printing

2017 ◽  
Author(s):  
Khaled Mostafa ◽  
A. J. Qureshi ◽  
Carlo Montemagno
Keyword(s):  
3D Printing ◽  
Layer Thickness ◽  
Exposure Time ◽  
Uv Light ◽  
Uv Exposure ◽  
Digital Light Processing ◽  
Black And White ◽  
Black Pixel ◽  
Price Range ◽  
Variable Light

3D printing manufacturing technology has been utilized in various applications due to its promising manufacturing advantages. Desktop Digital Light Processing (DLP) printers provide high-resolution products with a moderate price range. DLP uses an array of micromirrors to transmit UV light from the light projector in order to perform selective curing of a prepolymer resin and turn it in to the required geometry. The CAD file is transformed into several slices according to the layer thickness. Each slice is then converted to an image of black and white pixels, in which each white pixel actuates a corresponding micromirror to transmit the UV light to cure a corresponding voxel, while a black pixel corresponds to no actuation, which means no curing for the corresponding voxel. The micromirror’s size determines the resolution of the printer. Although a theoretical voxel size can be determined as a function of the micromirror’s dimensions and layer thickness, the actual voxel volume depends on several parameters such as the layer thickness, UV exposure time, and UV exposure intensity. Controlling these three parameters would result in more accurate 3D printed parts and more control over the dimensional tolerance. In this paper, the effect of variable light intensity in terms of grayscale pixels is studied along with the exposure time and layer thickness to manipulate the voxel horizontal dimensions. This enables printing with voxel dimensions below the size of the micromirrors in the DLP, which improve the geometric dimensioning and tolerance of the printed parts.

scholarly journals Mechanical Properties and Biocompatibility of Urethane Acrylate-Based 3D-Printed Denture Base Resin

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 822
Author(s):  
Jy-Jiunn Tzeng ◽  
Tzu-Sen Yang ◽  
Wei-Fang Lee ◽  
Hsuan Chen ◽  
Hung-Ming Chang
Keyword(s):  
Mechanical Properties ◽  
3D Printing ◽  
Flexural Modulus ◽  
Measurement Data ◽  
Uv Exposure ◽  
Control Group ◽  
Urethane Acrylate ◽  
Shore Hardness ◽  
Digital Light Processing ◽  
Denture Base

In this study, five urethane acrylates (UAs), namely aliphatic urethane hexa-acrylate (87A), aromatic urethane hexa-acrylate (88A), aliphatic UA (588), aliphatic urethane triacrylate diluted in 15% HDD (594), and high-functional aliphatic UA (5812), were selected to formulate five UA-based photopolymer resins for digital light processing (DLP)-based 3D printing. Each UA (40 wt%) was added and blended homogenously with ethoxylated pentaerythritol tetraacrylate (40 wt%), isobornyl acrylate (12 wt%), diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (3 wt%), and a pink acrylic (5 wt%). Each UA-based resin specimen was designed using CAD software and fabricated using a DLP 3D printer to specific dimensions. Characteristics, mechanical properties, and cytotoxicity levels of these designed UA-based resins were investigated and compared with a commercial 3D printing denture base acrylic resin (BB base) control group at different UV exposure times. Shore hardness-measurement data and MTT assays were analyzed using a one-way analysis of variance with Bonferroni’s post hoc test, whereas viscosity, maximum strength, and modulus were analyzed using the Kruskal–Wallis test (α = 0.05). UA-based photopolymer resins with tunable mechanical properties were successfully prepared by replacing the UA materials and the UV exposure times. After 15 min of UV exposure, the 5812 and 594 groups exhibited higher viscosities, whereas the 88A and 87A groups exhibited lower viscosities compared with the BB base group. Maximum flexural strength, flexural modulus, and Shore hardness values also revealed significant differences among materials (p < 0.001). Based on MTT assay results, the UA-based photopolymer resins were nontoxic. In the present study, mechanical properties of the designed photopolymer resins could be adjusted by changing the UA or UV exposure time, suggesting that aliphatic urethane acrylate has good potential for use in the design of printable resins for DLP-type 3D printing in dental applications.

Degradation of PVDF-based composite membrane and its impacts on membrane intrinsic and separation properties

2016 ◽  
Vol 36 (3) ◽  
pp. 261-268 ◽  
Author(s):  
Mei Jiun Lee ◽  
Chi Siang Ong ◽  
Woei Jye Lau ◽  
Be Cheer Ng ◽  
Ahmad Fauzi Ismail ◽  
...  
Keyword(s):  
Uv Irradiation ◽  
Exposure Time ◽  
Composite Membrane ◽  
Polyvinylidene Fluoride ◽  
Uv Light ◽  
Irradiation Time ◽  
Uv Exposure ◽  
Polymeric Membrane ◽  
Permeate Flux ◽  
Wastewater Treatment Process

Abstract In this work, an attempt was made to evaluate the effects of ultraviolet (UV) irradiation period on the intrinsic and separation properties of composite membrane composed of organic polyvinylidene fluoride and inorganic titanium dioxide (TiO2) nanoparticles by exposing the membrane to UV-A light for up to 250 h. The changes on membrane structural morphologies and chemical characteristics upon UV exposure were studied by field-emission scanning electron microscope and Fourier transform infrared, respectively. It was observed that some cracks and fractures were formed on the membrane outer surface when it was exposed to 120-h UV light. Further increase in UV irradiation time to 250 h had caused membrane structure to collapse, turning it into powder form. Filtration experiments showed that the permeate flux of irradiated membrane was significantly increased from 10.89 L/m2 h to 21.84 L/m2 h (>100% flux increment) while oil rejection decreased with increasing UV exposure time from 0 h to 120 h. Furthermore, the mechanical strength and thermal stability of irradiated membrane were also reported to decrease with increasing UV exposure time, suggesting the negative impacts of UV light on the membrane overall stability. This research is of particular importance to evaluate the suitability and sustainability of polymeric membrane, which is widely considered as the host for photocatalyts and used for wastewater treatment process under UV irradiation.

scholarly journals Characterization 0.1 wt.% Nanomaterial/Photopolymer Composites with Poor Nanomaterial Dispersion: Viscosity, Cure Depth and Dielectric Properties

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3948
Author(s):  
Rytis Mitkus ◽  
Marlitt Scharnofske ◽  
Michael Sinapius
Keyword(s):  
Dielectric Properties ◽  
3D Printing ◽  
Uv Light ◽  
Cost Effective ◽  
Digital Light Processing ◽  
Multi Walled Carbon Nanotubes ◽  
The Cost ◽  
Conductive Nanomaterials ◽  
Walled Carbon Nanotubes ◽  
Printing Techniques

Notably, 3D printing techniques such as digital light processing (DLP) have the potential for the cost-effective and flexible production of polymer-based piezoelectric composites. To improve their properties, conductive nanomaterials can be added to the photopolymer to increase their dielectric properties. In this study, the microstructure, viscosity, cure depth, and dielectric properties of ultraviolet (UV) light curable 0.1 wt.% nanomaterial/photopolymer composites are investigated. The composites with multi-walled carbon nanotubes (MWCNTs), graphene nanoplatelets (GNPs), and carbon black (CB) are pre-dispersed in different solvents (acetone, isopropyl alcohol, and ethanol) before adding photopolymer and continuing dispersion. For all prepared suspensions, a reduction in viscosity is observed, which is favorable for 3D printing. In contrast, the addition of 0.1 wt.% nanomaterials, even with poor dispersion, leads to curing depth reduction up to 90% compared to pristine photopolymer, where the nanomaterial dispersion is identified as a contributing factor. The formulation of MWCNTs dispersed in ethanol is found to be the most promising for increasing the dielectric properties. The post-curing of all composites leads to charge immobility, resulting in decreased relative permittivity.

A Benchmark Artifact to Evaluate the Manufacturing of Microfeatures by Digital Light Processing Stereolithography

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Lara Rebaioli ◽  
Irene Fassi
Keyword(s):  
Layer Thickness ◽  
Exposure Time ◽  
Process Parameters ◽  
Dimensional Accuracy ◽  
Main Process ◽  
Process Performance ◽  
Digital Light Processing ◽  
Specific Process ◽  
Experimental Campaign ◽  
Increasing Demand

Abstract Suitable benchmark artifacts are needed for assessing the technological capabilities and limitations of a specific process or for comparing the performances of different processes. Only a few benchmark artifacts have been specifically designed for features with microscale dimensions, even if their manufacturing is becoming very common due to the increasing demand for miniaturized parts or objects with microscale features. In this study, a suitable benchmark part is designed to evaluate the geometrical performance of a digital light processing (DLP) stereolithography (SLA) system for manufacturing microfeatures. The effect of the main process parameters (i.e., layer thickness and exposure time) and the feature position within the building platform on the process performance was assessed by a specifically studied experimental campaign. The results show that both the analyzed process parameters influence the minimum feasible size of protruding features and that the feature position influences the dimensional accuracy.

scholarly journals A Review of Vat Photopolymerization Technology: Materials, Applications, Challenges, and Future Trends of 3D Printing

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 598
Author(s):  
Marek Pagac ◽  
Jiri Hajnys ◽  
Quoc-Phu Ma ◽  
Lukas Jancar ◽  
Jan Jansa ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Additive Manufacturing ◽  
3D Printing ◽  
Uv Light ◽  
Construction Materials ◽  
Future Trend ◽  
Future Trends ◽  
New Materials ◽  
Digital Light Processing ◽  
Printing Techniques

Additive manufacturing (3D printing) has significantly changed the prototyping process in terms of technology, construction, materials, and their multiphysical properties. Among the most popular 3D printing techniques is vat photopolymerization, in which ultraviolet (UV) light is deployed to form chains between molecules of liquid light-curable resin, crosslink them, and as a result, solidify the resin. In this manuscript, three photopolymerization technologies, namely, stereolithography (SLA), digital light processing (DLP), and continuous digital light processing (CDLP), are reviewed. Additionally, the after-cured mechanical properties of light-curable resin materials are listed, along with a number of case studies showing their applications in practice. The manuscript aims at providing an overview and future trend of the photopolymerization technology to inspire the readers to engage in further research in this field, especially regarding developing new materials and mathematical models for microrods and bionic structures.

Development of fabrics by digital light processing three-dimensional printing technology and using a polyurethane acrylate photopolymer

2019 ◽  
Vol 90 (7-8) ◽  
pp. 847-856
Author(s):  
Seul Gi Kim ◽  
Ji Eun Song ◽  
Hye Rim Kim
Keyword(s):  
3D Printing ◽  
Layer Thickness ◽  
Three Dimensional ◽  
Curing Time ◽  
Printing Technology ◽  
Digital Light Processing ◽  
Three Dimensional Printing ◽  
3D Printing Technology ◽  
Polyurethane Acrylate ◽  
3D Printed

This study aimed to produce fabrics by the digital light processing (DLP) three-dimensional (3D) printing technology and using a polyurethane acrylate photopolymer as the printing material. The effect of the acrylate oligomer concentration on printing was evaluated. The DLP 3D printing conditions, such as the curing time and layer thickness, were controlled considering the physical properties, such as the tensile strength, elongation, and crease recovery of the 3D printed material. The optimal printing conditions were as follows: concentration of acrylate oligomer in the photopolymer: 10% (v/v); curing time per layer: 14 s; and layer thickness: 100 µm. These results are expected to guide further studies on the development of fabrics using DLP 3D printing technology.

scholarly journals Printability of External and Internal Structures Based on Digital Light Processing 3D Printing Technique

Pharmaceutics ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 207 ◽  
Author(s):  
Yan Yang ◽  
Yanjun Zhou ◽  
Xiao Lin ◽  
Qingliang Yang ◽  
Gengshen Yang
Keyword(s):  
3D Printing ◽  
Exposure Time ◽  
Drug Loading ◽  
In Vivo Evaluation ◽  
Digital Light Processing ◽  
Layer Height ◽  
Glycol Diacrylate ◽  
Internal Structures ◽  
Printing Technique

The high printing efficiency and easy availability of desktop digital light processing (DLP) printers have made DLP 3D printing a promising technique with increasingly broad application prospects, particularly in personalized medicine. The objective of this study was to fabricate and evaluate medical samples with external and internal structures using the DLP technique. The influence of different additives and printing parameters on the printability and functionality of this technique was thoroughly evaluated. It was observed that the printability and mechanical properties of external structures were affected by the poly(ethylene glycol) diacrylate (PEGDA) concentration, plasticizers, layer height, and exposure time. The optimal printing solutions for 3D external and internal structures were 100% PEGDA and 75% PEGDA with 0.25 mg/mL tartrazine, respectively. And the optimal layer height for 3D external and internal structures were 0.02 mm and 0.05 mm, respectively. The optimal sample with external structures had an adequate drug-loading ability, acceptable sustained-release characteristics, and satisfactory biomechanical properties. In contrast, the printability of internal structures was affected by the photoabsorber, PEGDA concentration, layer height, and exposure time. The optimal samples with internal structures had good morphology, integrity and perfusion behavior. The present study showed that the DLP printing technique was capable of fabricating implants for drug delivery and physiological channels for in vivo evaluation.

Sorbitol enhances the physicochemical stability of B12 vitamers

2020 ◽  
Vol 90 (5-6) ◽  
pp. 439-447 ◽  
Author(s):  
Andrew Hadinata Lie ◽  
Maria V Chandra-Hioe ◽  
Jayashree Arcot
Keyword(s):  
Ascorbic Acid ◽  
Uv Light ◽  
Heat Exposure ◽  
Water Soluble ◽  
Uv Exposure ◽  
Physicochemical Stability ◽  
Before And After ◽  
The Stability

Abstract. The stability of B12 vitamers is affected by interaction with other water-soluble vitamins, UV light, heat, and pH. This study compared the degradation losses in cyanocobalamin, hydroxocobalamin and methylcobalamin due to the physicochemical exposure before and after the addition of sorbitol. The degradation losses of cyanocobalamin in the presence of increasing concentrations of thiamin and niacin ranged between 6%-13% and added sorbitol significantly prevented the loss of cyanocobalamin (p<0.05). Hydroxocobalamin and methylcobalamin exhibited degradation losses ranging from 24%–26% and 48%–76%, respectively; added sorbitol significantly minimised the loss to 10% and 20%, respectively (p < 0.05). Methylcobalamin was the most susceptible to degradation when co-existing with ascorbic acid, followed by hydroxocobalamin and cyanocobalamin. The presence of ascorbic acid caused the greatest degradation loss in methylcobalamin (70%-76%), which was minimised to 16% with added sorbitol (p < 0.05). Heat exposure (100 °C, 60 minutes) caused a greater loss of cyanocobalamin (38%) than UV exposure (4%). However, degradation losses in hydroxocobalamin and methylcobalamin due to UV and heat exposures were comparable (>30%). At pH 3, methylcobalamin was the most unstable showing 79% degradation loss, which was down to 12% after sorbitol was added (p < 0.05). The losses of cyanocobalamin at pH 3 and pH 9 (~15%) were prevented by adding sorbitol. Addition of sorbitol to hydroxocobalamin at pH 3 and pH 9 reduced the loss by only 6%. The results showed that cyanocobalamin was the most stable, followed by hydroxocobalamin and methylcobalamin. Added sorbitol was sufficient to significantly enhance the stability of cobalamins against degradative agents and conditions.

UV Irradiation of Shell Eggs: Effect on Populations of Aerobes, Molds, and Inoculated Salmonella typhimurium

1997 ◽  
Vol 60 (6) ◽  
pp. 639-643 ◽  
Author(s):  
FUENG-LIN KUO ◽  
JOHN B. CAREY ◽  
STEVEN C. RICKE
Keyword(s):  
Salmonella Typhimurium ◽  
Uv Radiation ◽  
Uv Light ◽  
The Other ◽  
Uv Exposure ◽  
Microbial Populations ◽  
Aerobic Bacteria ◽  
Fluorescent Light ◽  
Uv Treatment ◽  
Shell Eggs

The effects were investigated of 254-nm UV radiation on populations of Salmonella typhimurium, aerobes, and molds on the shells of eggs. In the first experiment, the CFU of attached S. typhimurium cells on unwashed clean shell eggs were determined after 0, 1, 3, 5, and 7 min of UV treatment (620 μW/cm2) on both ends of the egg. All UV treatments significantly reduced S. typhimurium CFU (P &lt; .01). UVtreatment (620 μW/cm2) in 1-min alternating light and dark cycles for 5 min (three light and two dark) was compared to 0, 3, and 5 min of UV treatment. No significant differences in microbial populations were observed among light and dark cycles and the other UV treatments. In a subsequent experiment, the same UV treatments were utilized to evaluate photoreactivation. After UV exposure, eggs were exposed to 1 h of fluorescent light or I h of darkness or cultured immediately. S. typhimurium CFU were significantly (P &lt; .01) reduced by the UV treatments. However, no significant differences between microbial populations exposed to UV treatment and UV radiation plus photoreactivation were detected. For studies of aerobic bacteria and molds, different UV treatment times (0, 15, and 30 min) at the intensity of 620 μW/cm2 and different intensities (620, 1350, and 1720 μW/cm2) for 15 min were evaluated. Mold CFU per egg were either 0 or 1 for all UV treatments and a 99% reduction of CFU of aerobic bacteria per egg were observed for all UV treatments. It appears from these studies that UV light can significantly reduce populations of S. typhimurium, aerobes, and molds on shell eggs.

An experimental and theoretical study of the abrasion performance of digital light processing parts

2020 ◽  
pp. 095440542098133
Author(s):  
Mehdi Kazemi ◽  
Abdolreza Rahimi
Keyword(s):  
Layer Thickness ◽  
Normal Load ◽  
Digital Light Processing ◽  
One Step ◽  
Pin On Disk ◽  
The Relationship ◽  
Influential Parameters ◽  
Disk Method ◽  
Normal Angle

Generally, interactions at surface asperities are the cause of wear. Two-Thirds of wear in industry occurs because of the abrasive or adhesive mechanisms. This research presents an analytical model for abrasion of additive manufactured Digital Light Processing products using pin-on-disk method. Particularly, the relationship between abrasion volume, normal load, and surface asperities’ angle is investigated. To verify the proposed mathematical model, the results of this model are verified with the practical experiments. Results show that the most influential parameters on abrasion rate are normal load and surface’s normal angle. Abrasion value increases linearly with increasing normal load. The maximum abrasion value occurs when the surface’s normal angle during fabrication is 45°. After the asperities are worn the abrasion volume is the same for all specimens with different surface’s normal angle. Though layer thickness does not directly affect the wear rate, but surface roughness tests show that layer thickness has a great impact on the quality of the abraded surface. When the thickness of the layers is high, the abraded surface has deeper valleys, and thus has a more negative skewness. This paper presents an original approach in abrasion behavior improvement of DLP parts which no research has been done on it so far; thus, bringing the AM one step closer to maturity.

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