scholarly journals Influence of the scanning strategy parameters upon the quality of the SLM parts

2019 ◽  
Vol 41 ◽  
pp. 698-705 ◽  
Author(s):  
Sara Giganto ◽  
Pablo Zapico ◽  
Mª Ángeles Castro-Sastre ◽  
Susana Martínez-Pellitero ◽  
Paola Leo ◽  
...  
Keyword(s):  
Scanning Strategy ◽  
Strategy Parameters

scholarly journals Influence of Scanning Strategy Parameters on Residual Stress in the SLM Process According to the Bridge Curvature Method for AISI 316L Stainless Steel

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1659 ◽  
Author(s):  
Jiri Hajnys ◽  
Marek Pagáč ◽  
Jakub Měsíček ◽  
Jana Petru ◽  
Mariusz Król
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Process Parameters ◽  
316L Stainless Steel ◽  
Stress Generation ◽  
Aisi 316L ◽  
Laser Melting ◽  
Scanning Strategy ◽  
Aisi 316L Stainless Steel ◽  
Strategy Parameters

The present paper deals with the investigation and comparison of the influence of scanning strategy on residual stress in the selective laser melting (SLM) process. For the purpose of the experiment, bridge geometry samples were printed by a 3D metal printer, which exhibited tension after cutting from the substrate, slightly bending the samples toward the laser melting direction. Samples were produced with the variation of process parameters and with a change in scanning strategy which plays a major role in stress generation. It was evaluated using the Bridge Curvature Method (BCM) and optical microscopy. At the end, a recommendation was made.

scholarly journals The Influence of Process Parameters and Scanning Strategy on Lower Surface Quality of TA15 Parts Fabricated by Selective Laser Melting

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1228
Author(s):  
Junjie Jiang ◽  
Jianming Chen ◽  
Zhihao Ren ◽  
Zhongfa Mao ◽  
Xiangyu Ma ◽  
...  
Keyword(s):  
Surface Quality ◽  
Selective Laser Melting ◽  
Process Parameters ◽  
Flexible Manufacturing ◽  
Molten Pool ◽  
Lower Surface ◽  
Laser Melting ◽  
Scanning Strategy ◽  
Influence Of Process Parameters

With superior flexible manufacturing capability, selective laser melting (SLM) has attracted more and more attention in the aerospace, medical, and automotive industries. However, the poor quality of the lower surface in overhanging structures is still one of the factors that limits the wide application of SLM. In this work, the influence of process parameters and scanning strategy on the lower surface quality of SLMed TA15 (Ti-6Al-2Zr-1Mo-1V) titanium alloy parts were studied. The results showed that the laser surface energy density (EF) had a significant influence on the quality of the lower surface. Excessive EF led to obvious sinking of the molten pool and a serious slag hanging phenomenon. However, the too low EF easily contributed to the insufficient powder fusion in the lower surface area, which led to the agglomeration of a molten pool during core processing, resulting in slag hanging, pores, and powder spalling that reduced the quality of the lower surface. Moreover, the cross-remelting strategy and non-remelting strategy gained better surface quality at the low EF and high EF, respectively. In addition, it was found that the quality of the lower surface could be quickly and accurately evaluated by the cooling time of the molten pool during the processing of the lower surface. This research can increase the understanding of the forming mechanism of the lower surface and has certain guiding significance for the process optimization of the lower surface.

A Study on Effect of Different Process Parameters on the Quality of Overhang Surface Produced by Selective Laser Melting

2018 ◽  
Author(s):  
Sagar Sarkar ◽  
Ankit Porwal ◽  
Nuthalapati Yaswanth ◽  
Ashish Kumar Nath
Keyword(s):  
Aspect Ratio ◽  
Selective Laser Melting ◽  
Process Parameters ◽  
Support Structures ◽  
Metal Powders ◽  
Laser Melting ◽  
Scanning Strategy ◽  
Support Structure ◽  
Laser Process

Selective Laser Melting process enables production of geometrically complex parts directly from CAD model by melting metal powders layer by layer. For successful building of parts, some auxiliary structures namely support structures are also built to ensure proper heat conduction from actual parts to be built to the base plate. Support structures are needed if there are overhang surfaces in the design of the part. If the design of the part is very complex and features many overhang surfaces, then too many supports get generated. After building the part, these support structures need to be removed properly to get desired geometrical features and it may deteriorate the surface quality from where supports are removed. Sometimes removal of support structures becomes very difficult specially for parts having internal features. In this study, first effect of inclined angle, aspect ratio and different scanning strategies on the quality of overhang surfaces produced without any support structure under constant laser power and scan speed has been investigated. Scanning Electron Microscopy (SEM) images of overhang surfaces have been analyzed to investigate the presence of warping and uneven fused edges if any. It was found that with increase in inclined angles and aspect ratio, warping and presence of uneven fused edges increases. Rotational scanning strategy found to be better than linear alternate scanning strategy for reduced uneven fused edges formation and warping. Results show an overhang without any support structure can be built successfully with a single laser process parameters upto 25.343 degree which is less than theoretical critical angle of 26.565 degree. Further, it has been shown, using a novel strategy of building overhang with multiple laser process parameters, it is possible to build overhang even upto 24.132 degree.

Enhanced Image Coding Scheme Based on Modified Embedded Zerotree Wavelet Transform (DMEZW)

2017 ◽  
Vol 5 (4) ◽  
pp. 324
Author(s):  
Diyar W.N. Waysi ◽  
Adnan M.A. Brifcani
Keyword(s):  
Wavelet Transform ◽  
Image Coding ◽  
Signal To Noise Ratio ◽  
Low Frequency ◽  
High Compression Ratio ◽  
Lifting Wavelet Transform ◽  
Scanning Strategy ◽  
Coding Scheme ◽  
Encoding Efficiency

In this paper the proposed scheme uses different processing methods by applying Integer Lifting Wavelet Transform (ILWT) on gray scale image generating four subband is presented. The low frequency subbands is compressed losslessly by the Developed Modified Embedded Zerotree Wavelet Transform (DMEZW) directly. The high and middle frequency subbands are compressed lossyly by applying first to single stage Vector Quantization (VQ) then to DMEZW, finally generating two vectors ready for entropy coding and it is presented as Arithmetic Coding (AC) to produce a bit stream to be stored or transmitted. The main improvements of DMEZW is done by modifying the scanning strategy of the wavelet coefficients and the quantization threshold. The high and low frequency subbands are manipulated separately. The experimental results show that the developed method can improve the quality of the recovered image and the encoding efficiency. The proposed scheme programming code has achieved high Compression Ratio (CR) and remarkable Peak Signal to Noise Ratio (PSNR).

scholarly journals Mapping Spatial Distribution of Pores in an Additively Manufactured Gold Alloy Using Neutron Microtomography

2021 ◽  
Vol 11 (4) ◽  
pp. 1512
Author(s):  
Hossein Ghasemi-Tabasi ◽  
Pavel Trtik ◽  
Jamasp Jhabvala ◽  
Michael Meyer ◽  
Chiara Carminati ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Relative Density ◽  
3D Imaging ◽  
Gold Alloy ◽  
X Rays ◽  
Scanning Strategy ◽  
High Relative Density ◽  
Precise Tool ◽  
Non Destructive

A crucial criterion for the quality of the additively manufactured parts is the porosity content for achieving an acceptable final relative density. In addition, for jewelry applications, visible pores are unacceptable at or in the vicinity of the surface. In this study, non-destructive 3D neutron microtomography is applied to map the spatial distribution of pores in additively manufactured red-gold samples. The 3D imaging assessment underlines the high relative density of the printed red-gold sample and indicates residual pore sizes are predominantly below the limit of concern for jewelry applications. The 3D maps of pores within printed samples highlight the effect of the scanning strategy on the final quality and location of pores in the printed samples. These results confirm that neutron microtomography is a novel and precise tool to characterize residual porosity in additively manufactured gold alloys and other higher-Z materials where such investigation using other non-destructive methods (such as X-rays) is challenging due to the limited penetration depth.

A study on the surface quality of the 3D printed parts caused by the scanning strategy

2019 ◽  
Vol 25 (2) ◽  
pp. 247-254 ◽  
Author(s):  
Jitai Han ◽  
Yanan Ge ◽  
Yuxin Mao ◽  
Meiping Wu
Keyword(s):  
Surface Roughness ◽  
Surface Quality ◽  
Scanning Strategy ◽  
Clear Trend ◽  
Content Type ◽  
3D Printed ◽  
Side Face ◽  
Zigzag Shape ◽  
The Relationship

Purpose The purpose of this paper is to mainly focus on the relationship between the scanning strategy and surface quality. Surface quality, including surface roughness and flatness, is important for printed parts. So this paper optimizes the surface quality by changing the scanning strategy. Design/methodology/approach This paper is based on the phenomenon after the printed parts. A clear trend can be seen that the surface roughness on the side face shows a clear zigzag shape, so an optimized scanning strategy is used. Surface roughness in measured in macrostructure first by Mitutoyo and the flatness is measured by Hexagon Metrocogy. After that, microstructure on the side face is seen by RTEC to explain this phenomenon. Findings The surface quality on the side face shows a significant optimize by changing the scanning strategy. The surface quality on the positive face has some optimization to some degree. Originality/value This paper determines the relationship between the surface roughness on the side face and the scanning strategy. Few studies focus on the surface roughness, especially on the side face. Some studies try to optimize the surface roughness on the positive face. However, researchers always neglect the surface roughness on the side face. 2. This paper measures not only the surface roughness, but also the flatness. Surface roughness has a significant impact on the surface quality. However, it still has some limitations. Flatness is also measured to make this paper more representative. 3. This paper explains why scanning strategy can affect the surface quality. These images explain the research better and not just at the theoretical level.

scholarly journals Experiment of Process Strategy of Selective Laser Melting Forming Metal Nonhorizontal Overhanging Structure

Metals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 385 ◽  
Author(s):  
Wentian Shi ◽  
Peng Wang ◽  
Yude Liu ◽  
Guoliang Han
Keyword(s):  
Surface Roughness ◽  
Selective Laser Melting ◽  
Laser Power ◽  
316L Stainless Steel ◽  
Laser Melting ◽  
Scanning Strategy ◽  
Forming Quality ◽  
Forming Angle ◽  
Suspension Structure

To improve the precision of the nonhorizontal suspension structure and the forming quality of the overhanging surface by selective laser melting, the influence of laser power on the upper surface and the overhanging surface forming quality of 316L stainless steel at different forming angles was studied in the experiment. The influence of different scanning strategies, upper surface remelting optimization, and overhang boundary scanning optimization on the formation of overhanging structures was compared and analyzed. The forming effect of chromium–nickel alloy is better than 316L stainless steel below the limit forming angle in the overhanging structure. The better forming effect of chromium–nickel alloy can be obtained by narrowing the hatch space with the boundary optimization process. The experiment results show that the forming of the overhanging structure below the limit forming angle should adopt the chessboard scanning strategy. The smaller laser power remelting is beneficial to both the forming of the overhanging surface and the quality of upper surface forming. The minimum value of surface roughness using the 110 W power laser twice during surface remelting and boundary scanning 75° overhanging surface can reach 11.9 μm and 31.1μm, respectively. The forming accuracy error range above the limit forming angle is controlled within 0.4 mm, and the forming quality is better. A boundary count scanning strategy was applied to this study to obtain lower overhanging surface roughness values. This research proposes a process optimization and improvement method for the nonhorizontal suspension structure formed by selective laser melting, which provides the process support for practical application.

Immunoferritin localization of intracellular antigens in positively stained frozen sections

1978 ◽  
Vol 36 (2) ◽  
pp. 168-169
Author(s):  
K. T. Tokuyasu
Keyword(s):  
Surface Tension ◽  
Water Surface ◽  
Thin Layers ◽  
The Other ◽  
Positive Staining ◽  
Frozen Sections ◽  
The Past ◽  
Ultrathin Frozen Sections ◽  
Definition Of

During the past investigations of immunoferritin localization of intracellular antigens in ultrathin frozen sections, we found that the degree of negative staining required to delineate u1trastructural details was often too dense for the recognition of ferritin particles. The quality of positive staining of ultrathin frozen sections, on the other hand, has generally been far inferior to that attainable in conventional plastic embedded sections, particularly in the definition of membranes. As we discussed before, a main cause of this difficulty seemed to be the vulnerability of frozen sections to the damaging effects of air-water surface tension at the time of drying of the sections.Indeed, we found that the quality of positive staining is greatly improved when positively stained frozen sections are protected against the effects of surface tension by embedding them in thin layers of mechanically stable materials at the time of drying (unpublished).

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