Raster Lines Research Articles

Additive Manufacturing of Fiber‐Reinforced Zirconia‐Toughened Alumina Ceramic Matrix Composites by Material Extrusion‐Based Technology

Material extrusion‐based additive manufacturing becomes interesting to fabricate oxide ceramic matrix composites. Herein, 0–30 vol% alumina fibers are added to zirconia‐toughened alumina powder mixture and extruded into filaments. Shrinkage and mechanical properties of filaments and 3D‐printed samples are investigated. Thermomechanical analysis is conducted on filaments with and without fiber content indicating lower shrinkage in the direction of fiber alignment during the sintering process. The flexural strength of the extruded filaments and printed bars is measured through a 4‐point bending test. Filaments containing 15 vol% fiber exhibit the highest flexural strength of 110 MPa, with additional fiber content leading to a reduction in flexural strength. Using Weibull calculation, it is observed that printed bars without fibers result in significantly lower bending strength in comparison to the filaments because of the presence of printing failures. Bars with 10 vol% fibers, printed with 0° infill orientation achieve the same mechanical properties as the filaments, even though in microcomputed tomography gaps between printed lines and voids between raster lines can be observed. These results demonstrate that fiber reinforcement of ceramics offers a great potential to avoid the reduction of mechanical properties by printing defects.

Layer thickness influence on impact properties of FDM printed PLA material

Polylactic Acid (PLA) is a widely used material in Fused Deposition Modeling (FDM) technology. Additive Manufacturing (AM) parameters are known to have an influence on the mechanical properties of final components. In FDM, the layer thickness is an influencing parameter providing overall better mechanical properties with lower layer thickness values. In that case, the air gaps created between layers and raster lines have a lower share in total volume. However, layer over-compression might be an issue when choosing the lowest layer thickness options. This research paper investigates the impact properties of PLA material with variations in layer thickness namely, 0.1, 0.2, and 0.3 mm are considered here. Charpy tests were used for the impact property assessment, and all specimens were prepared with 100% infill percentage and honeycomb infill structure. Worth mentioning is that specimens have AMed notches. The impact tests were carried out on 7 specimens per batch (a total of 21 specimens). Therefore, obtained impact results from an instrumented pendulum were observed between groups to have an insight into the beneficial influence of lower layer thickness on impact properties and lower result scatter that finer layer resolution should produce.

Effect of Bergmeister papilla on disc parameters in spectral domain optical coherence tomography

ObjectivesTo investigate the morphological characteristics of Bergmeister papilla (BMP), a persistent hyaloid remnant tissue, and its effects on the measurements and repeatability of spectral-domain optical coherence tomography (OCT).Subjects/MethodsThe subjects of this prospective cross-sectional study including 83 patients with BMP and 76 unaffected individuals, all had open-angle structures. Images, including a 5-line raster and three consecutive optic disc cube scans centred on the optic disc, were acquired using the Cirrus high-definition OCT. BMP’s structural characteristics were classified based on the raster scan images, and repeatability of acquiring optic nerve head and retinal nerve fibre layer parameters acquisition was analysed by calculating the test-retest standard deviation (Sw), coefficient of variance (CV), and intraclass correlation coefficient.ResultsBMPs (n = 83) were categorised into lifting edge (LE) type (63.9%, n = 53), which partially covers the edge of the optic nerve head, and covering disc (CD) type (36.1%, n = 30), which completely covers the cupping area like a cap. The average cup-to-disc ratio (0.58 ± 0.21), vertical cup-to-disc ratio (0.55 ± 0.21), and cup volume (0.22 ± 0.22) of the CD type were lower than those of the LE type (0.66 ± 0.13, 0.64 ± 0.13, and 0.4 ± 0.27, respectively; all P < 0.05). Tolerability indices for repeatability of cup volume (Sw = 0.40 and CV = 0.36) and inferonasal (4 o’clock) retinal nerve fibre layer (Sw = 0.27 and CV = 0.25) in LE-type BMPs exceeded the cut-off value (0.22) and demonstrated stronger correlation with BMP location than that of the controls.ConclusionCaution should be exercised when interpreting OCT findings in eyes with BMP, as BMP can introduce a pitfall in OCT imaging.

Surface integrity of drilling Ti-6Al-4V micro-holes using the ultrashort pulse laser with different three-dimensional paths planning

The improvement of aero-engine performance posed a challenge to the heat dissipation ability of blades, resulting in a substantial increase in the demand for micron-sized (≤1 mm) film cooling holes. In this paper, an improved three-dimensional path machining method for ultrashort pulse laser drilling of Ti-6Al-4V titanium alloy is studied. The influence of four representative paths that are contour offset path, broken line path, raster path and jagged path on hole quality is described and discussed in detail. By establishing a three-dimensional two-temperature model in cylindrical coordinates, the defocusing control of the machining process is carried out, and the temperature field distribution with different drilling paths is simulated and analyzed. Finally, the experimental study of drilling round holes with a diameter of 800 μm is carried out on the titanium alloy Ti-6Al-4V plate with a thickness of 1 mm, and the wear resistance of the workpieces is tested. The experimental results show that, compared with the other three paths, the temperature field uniformity of laser processing with the contour offset path is the best, the quality of the processed holes is significantly improved, the outlet roundness is increased by 26.54 %–36.59 %, the cone angle is reduced by 12.7° and the wear resistance is increased by >1.3 times. Moreover, there is no obvious recast layer and micro cracks on the pore wall, and dense nano oxide particles are produced on the surface. In summary, the contour offset path controlled by three-dimensional defocusing is an effective hole processing path, which provides the possibility for machining efficient and high-quality film cooling holes.

Bergmeister papilla: A unilateral case report

To described enhanced imaging for visualization of anatomic features and microstructures of Bergmeister papilla within the optic nerve in asymptomatic patient.Primary measure is to see any change in the morphological characteristic in asymptomatic patient with Bergmeister papillae.Secondary outcome measures is to see any effect on parameters of OCT in asymptomatic patient with Bergmeister papillae. Carl Zeiss Cirrus HD 21 Line Raster OCT Model 5000 scanning protocol of the optic nerve and the optic disc cube 200×200 program obtains ONH images through a 3.46-mm diameter circle, and the algorithm automatically detects the circle and positions around the ONH and in the macular region were obtained in the both Eye. Fundus photo performed with Zeiss Fundus visucam 500.Clinical examination was carried out with Carl Zeiss Cirrus HD 21 Line Raster OCT Model 5000 scanning protocol of the optic nerve and the optic disc cube 200×200 program obtains ONH images through a 3.46-mm diameter circle was obtained in the both eye. Zeiss Cirrus HD 21 Line Raster OCT showed hyperreflectivity overlying traction on the right optic nerve with normal Foveal Contour while in the left eye (OS) optic nerve and macula were normal. Fundoscopic examination showed in the right eye(OD), a overlying traction was identified in the optic nerve supero-nasal region, while in the left eye(OS), the fundus was normal. Optical coherence tomography helps in identification of Bergmeister papilla with peripapillary vitreous thickening is beneficial in monitoring vitreo-retinal alterations that may cause future vision impairment.

ANALYSING THE INFLUENCE OF TECHNOLOGICAL PARAMETERS ON THE PROCESS OF LASER MARKING OF SURFACE OF ANODISED ALUMINIUM SAMPLES

The requirements for marking in terms of contrast and durability are constantly increasing. In order to meet all these challenges, it is necessary to carry out research leading to the optimisation and increase in efficiency of the technological process of laser marking. In the case of aluminium, the contrast and durability of the marking depend on the values of the laser marking parameters. In order to determine the optimal laser marking method, experimental studies have been carried out, controlling the power, speed, frequency, pulse duration and line raster step for a specific anodised aluminium. The studies carried out were analysed and subsequently optimized to obtain a contrast marking. A Rofin PowerLine F 20 Varia fiber laser system and aluminium alloy 1050 with anodised surface were used for the research. The surface changes after the laser treatment were analysed using a laser scanning microscope and contrast determination method. The dependence of contrast and roughness on speed, power, frequency and raster step was analysed. Comparative plots of contrast and roughness variations versus laser marking technological parameters were constructed.

Investigation of the change in wettability properties and corrosion behavior of AISI 304 after laser surface texturing

Stainless steel is a widely used material in industry, architecture, and medical instruments. However, after various thermal processing of stainless steels, chromium carbides can be formed, which locally depletes the chromium available to form a passive film and reduces the corrosion performance. Laser surface treatment can change the surface chemistry of the steel and improve some electrochemical characteristics. However, these characteristics are influenced by the laser power, pulse width, distance between the lines, scanning speed, etc., which all change the surface chemistry and characteristics of laser surface texturing. Simultaneously, the ability to repel liquids that cause corrosion actions could combine to enhance corrosion performance. Since the wettability of a solid surface depends both on its topography and chemical nature, the micro structuring of an austenitic steel surface is an effective way of fabricating hydrophobic or super hydrophobic corrosion-resistant surfaces. For this reason, this study discusses the effect of laser power in the impact zone and the distance between raster lines on the microstructure, wettability, and corrosion resistance of austenitic steel (AISI 304) when exposed to nanosecond fiber laser radiation. The results indicate that parameter-controlled micro structuring can be used to form both hydrophilic and hydrophobic surfaces with different electrochemical performances.

Real-time process monitoring and closed-loop control on laser power via a customized laser powder bed fusion platform

Additive manufacturing (AM) is one of the most effective ways to fabricate parts with complex geometries using various materials. However, AM also suffers from printing quality issues resulting from the defects such as over-melt, lack of fusion, swelling, etc. One of the root causes of those issues is that the process parameters remain constant during the entire printing process, regardless of the dynamic heat accumulation and various printing feature sizes. For instance, raster is the most common scanning strategy in the laser powder bed fusion (L-PBF) process. The length of the raster line varies depending on the printing feature size. When scanning small features, the raster line is short, resulting in heat accumulations and over-melt. These variabilities may cause severe quality issues and thus suggest adaptive process parameters be applied. Aiming to address this challenge, this study develops a closed-loop control system to regulate the laser power based on melt pool thermal emission to avoid over-melt, balling, and high surface roughness. The control target is determined by correlating the printing quality (dimensional printing error in this study) with the thermal emission through thin-line printing trials using variable power. A high-speed thermal sensor and controller are designed, tuned, and implemented on a newly developed L-PBF testbed. The system successfully maintains a low dimensional error by regulating the laser power at 2 kHz. A significant improvement in printing quality was achieved, as validated by both microscopic imaging and 3D scanning.

Improvement of line image reproduction in the system of prepress engineer work

In order to optimise the process of prepress engineer work, it is necessary to provide a high-quality display of the line image, which ensures the most accurate transfer of the geometric dimensions of individual elements. The purpose of the article was to determine the degree of influence of the binarization threshold on the resolution value of raster line images. The experiments were based on the use of general scientific methods of analysis, generalisation, classification, deduction. To assess the quality of line image reproduction in this paper, photoforms were employed using a line test object which was designed as an accurate photograph with the use of an optical density distribution profile. The paper examines the influence of various parameters of raster structures on the playback quality of reproductions. The specifics of using a photo output device as the main link, which ensures the reproduction quality of image details, have been determined. The geometry of the raster structure when using rotation angles with rational tangents has been analysed. Features of the Accurate Screening technology have been systematised. The difference between “rational” and “irrational” rasterization methods has been considered. The main aspects of the use of line details in the reproduction process have been considered. The proposed method for assessing the quality of a line image reproduction with an uneven edge has been called the “signal-to-noise ratio” method, and it has been concluded that the scanning stage affects the quality of image reproduction to a greater extent than the photo output. The practical result of the work is the development of recommendations that can find practical application in reproduction processes. The developed binarization algorithms allow processing of images with significant zonal brightness unevenness, with monotonous brightness areas, and highly noisy images

Parallel tool-path generation for Additive Manufacturing: A GPU-based zigzag filling

This paper presents a parallel zigzag (raster) tool-path generation method for Additive Manufacturing (AM). Based on the analysis of some ordinary serial algorithms, it was observed that some compute-intensive operations could be parallelized by using a Graphics Processing Unit (GPU) architecture. However, to achieve this, many challenges were faced and solved by designing a method to work concurrently with individual contour segments on multiple layers while keeping the data organized. The method’s ability to solve the zigzag generation problem was verified, and its performance was measured by running an exhaustive search for optimal raster angles to reduce manufacturing time. The results showed that the method was effective and generated relevant computational gain, being up to 9 times faster than its serial counterpart. In the tool-path optimization, the simulations found configurations yielding an average length of raster lines up to 38% longer, which, in turn, can reduce manufacturing time.

Collaborative Music Creation Method Based on Image Collection of Lattice Code

With the development of science and technology, more and more emerging technologies have been integrated into electronic music, forming a rich and diverse form of interactive electronic music. This research mainly discusses the collaborative music creation method based on bit matrix code image acquisition. In the decoding process, the displacement value of each point should be determined according to the direction and distance from the point to the reference point of the corresponding grid raster. This article marks the position characteristics of image symbols according to the dot matrix code notation defined in the improved coding method. After searching for a pair of dot codes with the shortest distance in the horizontal or vertical direction, starting from the first code point in the vertical direction and following the second code point. Through the above method, it is possible to accurately construct the grid raster lines of the dot matrix position encoding symbol image formed after the improved encoding, so that the decoding of the dot matrix symbol image is more accurate, and the composition translation is reduced. The improved coding method reduces the error of the origin matrix code by about 0.11 mm as a whole. This research will realize the collaborative recording of data in the music creation process, which will bring great convenience to creators.

Parametric Effects of Fused Filament Fabrication Approach on Surface Roughness of Acrylonitrile Butadiene Styrene and Nylon-6 Polymer.

This research objective is to optimize the surface roughness of Nylon-6 (PA-6) and Acrylonitrile Butadiene Styrene (ABS) by analyzing the parametric effects of the Fused Filament Fabrication (FFF) technique of Three-Dimensional Printing (3DP) parameters. This article discusses how to optimize the surface roughness using Taguchi analysis by the S/N ratio, ANOVA, and modeling methods. The effects of ABS parameters (initial line thickness, raster width, bed temperature, build pattern, extrusion temperature, print speed, and layer thickness) and PA-6 parameters (layer thickness, print speed, extrusion temperature, and build pattern) were investigated with the average surface roughness (Ra) and root-mean-square average surface roughness (Rq) as response parameters. Validation tests revealed that Ra and Rq decreased significantly. After the optimization, the Ra-ABS and Rq-PA-6 for the fabricated optimized values were 1.75 µm and 21.37 µm, respectively. Taguchi optimization of Ra-ABS, Rq-ABS, Ra-PA-6, and Rq-PA-6 was performed to make one step forward to use them in further research and prototypes.

Influence of Raster Pattern on Residual Stress and Part Distortion in FDM of Semi-Crystalline Polymers: A Simulation Study.

In fused deposition modelling (FDM) based on the selected raster pattern, the developed internal thermal residual stresses can vary considerably affecting the mechanical properties and leading to distinct part distortions. This phenomenon is more pronounced in semi-crystalline than amorphous polymers due to crystallisation. Hence, this study focuses on the simulation of the FDM process of a semi-crystalline polymer (polypropylene) with raster patterns such as line (90°/90°), line (0°/90°), zigzag (45°/45°), zigzag (45°/−45°), and concentric from Cura (slicing software). The simulation provides visualisation and prediction of the internally developed thermal residual stresses and resulting warpage with printing time and temperature. The sample with a line (90°/90°) raster pattern is considered as the reference sample in order to compare the relative levels of residual stress and warpage in the other printed/simulated samples. Among the considered raster patterns, the concentric pattern displays the lowest amount of warpage (5.5% decrease) along with a significant drop in residual stress of 21%. While the sample with a zigzag (45°/−45°) pattern showed the highest increase of 37% in warpage along with a decrease of 9.8% in residual stresses. The sample with a zigzag (45°/45°) pattern, exhibited a considerable increase of 16.2% in warpage with a significant increase of 31% in residual stresses. Finally, the sample with a line (0°/90°) raster pattern displayed an increase of 24% increase in warpage with an increase of 6.6% in residual stresses.

End-to-End Line Drawing Vectorization

Vector graphics is broadly used in a variety of forms, such as illustrations, logos, posters, billboards, and printed ads. Despite its broad use, many artists still prefer to draw with pen and paper, which leads to a high demand of converting raster designs into the vector form. In particular, line drawing is a primary art and attracts many research efforts in automatically converting raster line drawings to vector form. However, the existing methods generally adopt a two-step approach, stroke segmentation and vectorization. Without vector guidance, the raster-based stroke segmentation frequently obtains unsatisfying segmentation results, such as over-grouped strokes and broken strokes. In this paper, we make an attempt in proposing an end-to-end vectorization method which directly generates vectorized stroke primitives from raster line drawing in one step. We propose a Transformer-based framework to perform stroke tracing like human does in an automatic stroke-by-stroke way with a novel stroke feature representation and multi-modal supervision to achieve vectorization with high quality and fidelity. Qualitative and quantitative evaluations show that our method achieves state of the art performance.

THE RESEARCH OF QUALITY OF THERMOTRANSFER PRINT IMAGES ON COTTON TEXTILE MATERIAL

The article presents thermogravimetric studies of cotton textile material before and after printing by thermal transfer printing. Thermal transfer printing on garments and knitwear, umbrellas, bags, advertising banners, posters, etc. is popular. Transfer printing technology involves the transfer of the image to the textile material using an intermediate medium. First, the desired image is formed on a special paper or film using screen printing. Then, with the help of temperature in special presses, it is transferred to the textile material. If the image is multicolored, the whole process is repeated separately for each color. Heat transfer technology allows to apply high- and multi-color images to finished products or semi-finished products with high accuracy; to carry out personalized printing. Since thermal transfer printing involves the presence of high temperatures to obtain an image on the material, a comprehensive thermal analysis of cotton fabric was performed before and after printing. A test scale with a raster line from 100 to 140 lines / cm was used for research. Densitometric indicators of quality of the formed thermotransfer images by plastezol paints are given. It is established that with the increase of the line of raster images the color indicators of the prints on the textile material decrease slightly, which must be taken into account when fulfilling orders in industrial conditions. Using electron microscopy, the process of interaction of dye with cotton fibers in the fixation of printed images was studied. Significant influence on the quality of prints on textile material of surface structure of cotton fibers, their structure, dye composition and printing modes is confirmed. It is established that cotton fabric with printed image at 140 oC provides high quality color printed thermal transfer images. This is confirmed by such qualimetric indicators as optical density, image contrast, brightness. Modeling the mechanism of fixing the printed image on the fabric during thermal transfer printing can be divided into four stages: diffusion of the dye from the environment to the surface of the fibers; sorption of the dye on the surface; diffusion of dye inside the fiber; sorption of the dye on the inner surface of the fiber, which require more detailed and in-depth studies.

Stereolithographic additive manufacturing of acoustic devices with spatially modulated cavities

AbstractStereolithographic additive manufacturing (STL‐AM) has been developed to create practical components with functional geometries. Nanoparticles are mechanically dispersed into photosensitive resins, and the resulting mixed paste is thinly spread on a flat substrate. One‐dimensional (1D) raster lines were cured via ultraviolet laser scanning. Two‐dimensional (2D) cross‐sections are formed by adjacent joining. Three‐dimensional (3D) solid structures are fabricated via lamination bonding. The composite precursors were dewaxed and sintered under optimized heat treatment conditions. Computer‐aided design, manufacture, and evaluation (CAD/CAM/CAE) processes of acoustic devices with rigid alumina structures will be progressively reviewed. Cylindrical cavities were divided into self‐similar volumes as harmonic instruments to perform overtone sounds. Spherical cavities were connected with steric junctions as noise suppressors to exhibit absorption bands. Qualitative improvements in social and industrial environments by using stereolithographic technologies are discussed and practically demonstrated.

3D-printed polylactide/hydroxyapatite/titania composite filaments

In this study, polylactic acid (PLA) based polymer composite filaments containing titanium dioxide (titania, TiO2), synthetic hydroxyapatite (HA), and natural hydroxyapatite (NHA) have been developed for biomedical applications. By using these composite filaments fabricated, 3D prints were easily printed on the fused deposition modeling (FDM) printer. The chemical and physical properties of PLA/HA/NHA/TiO2 composite prints were investigated. According to the DSC/TGA analysis of the 3D printing samples, the maximum operating temperature of the composites formed in PLA/HA/NHA/TiO2 blends was approximately 300 °C. With the addition of 1% HA/4% TiO2 to PLA, the glass transition temperature was 71 °C and the melting temperature was 167 °C. According to FTIR analysis, HA/NHA/TiO2 additives did not cause a change in the chemical structure of PLA. According to SEM analysis, TiO2 caused raster gaps to decrease and HA caused raster lines to be smoother. In EDX and Mapping analysis, it was seen that HA/NHA/TiO2 was homogeneously distributed in PLA. Stirring the PLA/HA/NHA/TiO2 mixtures at 100 rpm for 12 h was sufficient for homogeneous distribution.

Comparison of Two Spectral-domain Optical Coherence Tomography Scan Modes for Measuring Retinal Vessel Diameter

ABSTRACT Purpose: To assess the agreement between Line 3–5 raster scan mode and circular scan mode for measuring retinal vessel diameter, and to analyze the influence of scanning distance on retinal vessel diameter and agreement. Methods: 79 healthy participants (79 eyes) were scanned with two modes. The scanning distance was defined as the distance from the center of the optic disc to the intersection of the blood vessel and the scan line on the raster image. The large superior temporal vessel was measured, with the distance between vascular wall hyperreflectivities measured to obtain vessel diameters. The degree of agreement between the line 3–5 raster scan and circular scan modes, and the effect of scanning distance on agreement and vascular diameter were assessed. Results: There was good agreement between line 3 subgroup and the circular scan for measuring venous and arterial diameter (venous: intraclass correlation coefficients (ICCs) = 0.87, p < .001; arterial: ICCs = 0.84, p < .001). Unexpectedly, diameters from the fourth raster scan were only comparable to the circular scan in measuring venous diameter (ICCs = 0.86, p < .001), despite the same scanning distance between the fourth raster line and circular scan. Vessels with a scanning distance between 1400 μm – 1799 μm showed good agreement with the circular scan (venous and arterial: all ICCs ≥ 0.84, p < .001). In addition, venous diameter and arterial diameter decreased with increasing distance from the optic disc center, with venous and arterial diameter decreasing by 0.02 μm/μm (p < .001) and 0.007 μm/μm (p = .02), respectively. Conclusion: Arterial and venous diameter measured by the circular mode was comparable to only one scan line and two scan lines of the raster scan mode, respectively. Our study identified a difference between the two scan modes, with the difference not fully attributable to differences in scanning distance. Prospective studies reporting vascular diameter as a primary outcome should report the scan mode used.

Prediction of part distortion in Fused Deposition Modelling (FDM) of semi-crystalline polymers via COMSOL: Effect of printing conditions

Residual stresses and warpage adversely affect the dimensional accuracy and performance of 3D-printed semi-crystalline polymers in Fused Deposition Modelling (FDM). One of the main challenges in FDM is to understand and relate the impact of printing conditions on part distortion for optimizing the 3D-printing process to achieve good print quality. Hence, the effect of various printing parameters, particularly print bed temperature, layer bonding, layer thickness and raster pattern, on built-up residual stresses and warpage is simulated in this work, by building a relationship between the crystallisation kinetics, viscoelastic and thermo-mechanical properties of the polymer in relation to changes in temperature during FDM using element activation in COMSOL. To the best of our knowledge, this is a novel approach for quantitative prediction of part distortion in FDM of semi-crystalline polymers under various printing conditions. Based on the simulation results, it is observed that a decrease in layer thickness from 0.5 mm to 0.1 mm results in an 89% drop in warpage and a reduction in residual stress of 24%. Applying a line raster pattern reduces warpage and residual stresses by 16% and 36%, respectively in comparison with a zigzag raster pattern. Very good agreement is observed between simulation and experimental results for warpage under various printing conditions. The results of this study can be used to predict and/or minimise part distortion in a semi-crystalline, 3D-printed polymer by simulating the effect of printing parameters on residual stresses during FDM.

Analysis of the process of laser ablation of marble surfaces

Over the last decade, laser surface treatment of stones has gained increasing scientific interest. New technologies and processes based on different types of laser sources and processing modes are being studied. This report examines the process of laser ablation of a marble surface using a fiber laser. Three factors influencing the process of laser marking and engraving were studied: laser power, processing speed and step between raster lines. The functional dependencies between these factors and the contrast of the obtained graphic image are established. The optimal operating intervals for this group of technological parameters are analyzed. Thanks to the very-high-definition laser ablation, inscriptions, drawings and images can be re-created and processed with unique accuracy. In addition, the reduction of manufacturing time and resources used in the process makes this technology an environmentally-friendly and extremely cost-efficient solution.