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1
Yan, Xiaoling, Xiansheng Xu, and Qinxue Pan. "Study on the Measurement of Stress in the Surface of Selective Laser Melting Forming Parts Based on the Critical Refraction Longitudinal Wave." Coatings 10, no. 1 (December 19, 2019): 5. http://dx.doi.org/10.3390/coatings10010005.
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Measurement and control of stress in the metal forming layer is the basic problem of selective laser melting (SLM) forming parts. The critical refraction longitudinal (LCR) wave method to test stress in metallic materials has been extensively studied. However, when testing of stress in selective laser melting (SLM) forming parts using this method, some deep-seated regularities of this technology are still not clear. In order to reveal the mechanism of the LCR wave method to measure stress in SLM forming parts, specimens made of 316 L stainless steel were manufactured using meander, stripe, and chessboard scanning strategies. Static load tensile test were applied to SLM forming specimens, with the purpose to demonstrate the scanning strategy has important effect on the LCR wave method to test stress in SLM forming parts. The regularity of the LCR wave velocity on stress is obtained in this study. The anisotropic microstructure of SLM forming parts has an unneglectable effect on the LCR wave stress test. The essential principle of anisotropic microstructure effecting the LCR wave velocity in SLM forming parts were revealed in the experiments. The results of the experiment provide a basis for non-destructive and reliable test of stress in SLM forming parts and other inhomogeneous materials.
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Liu, A., Chee Kai Chua, and Kah Fai Leong. "Properties of Test Coupons Fabricated by Selective Laser Melting." Key Engineering Materials 447-448 (September 2010): 780–84. http://dx.doi.org/10.4028/www.scientific.net/kem.447-448.780.
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Selective Laser Melting (SLM) is a popular and promising Additive Manufacturing (AM) technique as it can produce parts with complex internal features with part density close to 100%. However, unprocessed raw SLM fabricated parts have surface roughness issues and the mechanical properties of raw SLM parts without heat treatment are not ideal. The material used to address some of these issues in this research is an Aluminum alloy, AlSi10Mg – a strong and light weight metal. The SLM machine engaged for the test coupons fabrication is M2 Cusing from Concept Laser, Germany, which uses a diode pumped Yb-Fibre laser (Ytterbium-doped fibre lasers) with an effective output power of 200W. It is found that SLM fabricated parts with and without sandblasting shows up to 80% difference in surface roughness values. Also, the tensile test experiments of raw untreated SLM parts carried out at room temperature and at high temperature (200oC) show superior result compared with heat treated casted parts. Other properties such as hardness and density (porosity) are found to be better than heat treated cast parts as well.
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Liu, Jin Hui, Wen Juan Xie, Sheng Bing Xiao, Wei Ling Zhao, and Jia Zhang. "On Formation and Estimation of Pores during Selective Laser Melting of Single-Phase Metal Powders." Advanced Materials Research 338 (September 2011): 94–101. http://dx.doi.org/10.4028/www.scientific.net/amr.338.94.
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Porous metals are applied in many more fields than other porous materials. Pores in porous metal parts manufactured by selective laser melting (SLM) should not be regarded as defects but favorable characters because they are the main composition of porous metal parts. Therefore, fully densification is not the only target in forming metal parts via SLM. The formation mechanism of pores in SLM is studied mathematically in this article, and mathematical model is built to describe the formation mechanism. It is concluded that the shape of pores and the porosity of parts are the function of SLM processing parameters and the diameter of powder particles. Pores can be controlled and estimated by adjusting processing parameters and the nature of forming materials. Porous metal parts produced by SLM can be applied in many more fields owing that SLM technology is flexible to change the shape of these part and the nature of materials.
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Wang, Di, Yang Liu, Yongqiang Yang, and Dongming Xiao. "Theoretical and experimental study on surface roughness of 316L stainless steel metal parts obtained through selective laser melting." Rapid Prototyping Journal 22, no. 4 (June 20, 2016): 706–16. http://dx.doi.org/10.1108/rpj-06-2015-0078.
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Purpose The purpose of this paper is to provide a theoretical foundation for improving the selective laser melting (SLM) surface roughness. To improve the part’s surface quality during SLM process, the upper surface roughness of SLM parts was theoretically studied and the influencing factors were analyzed through experiments. Design/methodology/approach The characteristics of single track were first investigated, and based on the analysis of single track, theoretical value of the upper surface roughness would be calculated. Two groups of cubic sample were fabricated to validate SLM parts’ surface roughness, the Ra and relative density of all the cubic parts was measured, and the difference between theoretical calculation and experiment results was studied. Then, the effect of laser energy density on surface roughness was studied. At last, the SLM part’s surface was improved by laser re-melting method. At the end of this paper, the curved surface roughness was discussed briefly. Findings The SLM upper surface roughness is affected by the width of track, scan space and the thickness of powder layer. Measured surface roughness Ra value was about 50 per cent greater than the theoretical value. The laser energy density has a great influence on the SLM fabrication quality. Different laser energy density corresponds to different fabricating characteristics. This study divided the SLM fabrication into not completely melting zone, balling zone in low energy density, successfully fabricating zone and excessive melting zone. The laser surface re-melting (LSR) process can improve the surface roughness of SLM parts greatly without considering the fabricating time and stress accumulation. Originality/value The upper surface roughness of SLM parts was theoretically studied, and the influencing factors were analyzed together; also, the LSR process was proven to be effective to improve the surface quality. This study provides a theoretical foundation to improve the surface quality of SLM parts to promote the popularization and application of metal additive manufacturing technology.
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Franz, Peter, Aamir Mukhtar, Warwick Downing, Graeme Smith, and Ben Jackson. "Mechanical Behaviour of Gas Nitrided Ti6Al4V Bars Produced by Selective Laser Melting." Key Engineering Materials 704 (August 2016): 225–34. http://dx.doi.org/10.4028/www.scientific.net/kem.704.225.
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Gas atomized Ti-6Al-4V (Ti64) alloy powder was used to prepare distinct designed geometries with different properties by selective laser melting (SLM). Several heat treatments were investigated to find suitable processing parameters to strengthen (specially to harden) these parts for different applications. The results showed significant differences between tabulated results for heat treated billet Ti64 and SLM produced Ti64 parts, while certain mechanical properties of SLM Ti64 parts could be improved by different heat treatments using different processing parameters. Most heat treatments performed followed the trends of a reduction in tensile strength while improving ductility compared with untreated SLM Ti64 parts.Gas nitriding [GN] (diffusion-based thermo-chemical treatment) has been combined with a selected heat treatment for interstitial hardening. Heat treatment was performed below β-transus temperature using minimum flow of nitrogen gas with a controlled low pressure. The surface of the SLM produced Ti64 parts after gas nitriding showed TiN and Ti2N phases (“compound layer”, XRD analysis) and α (N) – Ti diffusion zones as well as high values of micro-hardness as compared to untreated SLM produced Ti64 parts. The microhardness profiles on cross section of the gas nitrided SLM produced samples gave information about the i) microhardness behaviour of the material, and ii) thickness of the nitrided layer, which was investigated using energy dispersive spectroscopy (EDS) and x-ray elemental analysis. Tensile properties of the gas nitrided Ti64 bars produced by SLM under different conditions were also reported.
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Bâlc, Nicolae, Sorin Cosmin Cosma, Julia Kessler, and Voicu Mager. "Research on Improving the Outer Surface Quality of the Parts Made by SLM." Applied Mechanics and Materials 808 (November 2015): 199–204. http://dx.doi.org/10.4028/www.scientific.net/amm.808.199.
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The paper presents an application of the ANOVA method within the Selective Laser Melting (SLM) process. A new mathematical model was developed, to calculate the surface roughness of the SLM parts made from titanium powder, as function of the important SLM parameters: point distance, exposure time and laser power. Preliminary experiments were undertaken according to the Design Experts work plan and the new mathematical formula was tested by further experimental research, to validate the optimized SLM parameters.
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BOJKO, Łukasz, Wojciech RYNIEWICZ, Anna M. RYNIEWICZ, Marcin KOT, and Paweł PAŁKA. "THE INFLUENCE OF ADDITIVE TECHNOLOGY ON THE QUALITY OF THE SURFACE LAYER AND THE STRENGTH STRUCTURE OF PROSTHETIC CROWNS." Tribologia 280, no. 4 (August 1, 2018): 13–22. http://dx.doi.org/10.5604/01.3001.0012.7480.
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Prosthetic crowns reproduce the damaged hard structures of the patient’s own teeth and take over their natural functions, thus securing the correct reconstruction of the stomatognathic system. The aim is to evaluate the crowns for premolars and molars produced by casting, milling, and Selective Laser Melting technologies, in terms of the accuracy of reproducing the degree against the prosthetic pillar, the analysis of the surface layer structure of the step, and the micromechanical parameters of the alloy. The study material included CoCrMo alloy crowns. The conducted study allowed finding that the tightness of prosthetic crowns made using traditional casting technology as well as in SLM milling and technology is comparable and meets clinical requirements. Structural crown analyses confirmed the very good quality of the surface layer obtained with milling technology and SLM technology using the CAD/CAM method. SLM and digital milling allow the formation of precise and durable structures constituting the foundation of crowns in a time much shorter than the casting process.
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Wang, Zhi Gang, Yu Sheng Shi, Rui Di Li, Qing Song Wei, and Jin Hui Liu. "Manufacturing AISI316L Components via Selective Laser Melting Coupled with Hot Isostatic Pressing." Materials Science Forum 675-677 (February 2011): 853–56. http://dx.doi.org/10.4028/www.scientific.net/msf.675-677.853.
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Selective laser melting (SLMing) is a new advanced material processing technology which is used in fabricating parts with complex shape. Hot isostatic pressing (HIPing) is a manufacture technology which forms parts by imposing high heat and pressure on metal powders or semi-manufactured parts. Considering the advantages of both the technologies, they can be combined to produce higher-quality parts free from the limitation of the shape of parts. AISI316L stainless steel is widely used in manufacturing varies of complex metal parts. In this research, three AISI316L stainless steel samples with different relative densities were acquired by controlling the fabricating parameters in SLM. The SEM and optical microscopy analysis were employed to characterize the relative density, microstructure, deformation by comparing the differences between SLM samples and SLM-HIPped samples. In addition, the influence of HIP process on microstructures of samples in different laser fabricating parameters was investigated by analyzing the mechanisms of SLM and HIP. The results show that HIP can close vacuum crack and pore, consequently, the relative density of SLM samples increases after HIP, making the property of the samples improved and microstructure better-distributed. Moreover, the increment of relative density under the same HIP condition is also discussed.
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Lin, Zhenqiang, Yiwen Lai, Taotao Pan, Wang Zhang, Jun Zheng, Xiaohong Ge, and Yuangang Liu. "A New Method for Automatic Detection of Defects in Selective Laser Melting Based on Machine Vision." Materials 14, no. 15 (July 27, 2021): 4175. http://dx.doi.org/10.3390/ma14154175.
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Selective laser melting (SLM) is a forming technology in the field of metal additive manufacturing. In order to improve the quality of formed parts, it is necessary to monitor the selective laser melting forming process. At present, most of the research on the monitoring of the selective laser melting forming process focuses on the monitoring of the melting pool, but the quality of forming parts cannot be controlled in real-time. As an indispensable link in the SLM forming process, the quality of powder spreading directly affects the quality of the formed parts. Therefore, this paper proposes a detection method for SLM powder spreading defects, mainly using industrial cameras to collect SLM powder spreading surfaces, designing corresponding image processing algorithms to extract three common powder spreading defects, and establishing appropriate classifiers to distinguish different types of powder spreading defects. It is determined that the multilayer perceptron (MLP) is the most accurate classifier. This detection method has high recognition rate and fast detection speed, which cannot only meet the SLM forming efficiency, but also improve the quality of the formed parts through feedback control.
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Król, M., J. Mazurkiewicz, and S. Żołnierczyk. "Optimization and analysis of porosity and roughness in selective laser melting 316L parts." Archives of Materials Science and Engineering 1, no. 90 (March 1, 2018): 5–15. http://dx.doi.org/10.5604/01.3001.0012.0607.
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Purpose: The investigations have been carried out on 316L stainless steel parts fabricated by Selective Laser Melting (SLM) technique. The study aimed to determine the effect of SLM parameters on porosity, hardness, and structure of 316L stainless steel. Design/methodology/approach: The analyses were conducted on 316L stainless steel parts by using AM125 SLM machine by Renishaw. The effects of the different manufacturing process parameters as power output, laser distance between the point’s melted metal powder during additive manufacturing as well as the orientation of the model relative to the laser beam and substrate on porosity, hardness, microstructure and roughness were analysed and optimised. Findings: The surface quality parts using 316L steel with the assumed parameters of the experiment depends on the process parameters used during the SLM technique as well as the orientation of formed walls of the model relative to the substrate and thus the laser beam. The lowest roughness of 316L SLM parts oriented perpendicularly to the substrate was found when 100 W and 20 μm the distance point was utilised. The lowest roughness for part oriented at 60° relatives to the substrate was observed when 125 W and the point distance 50 μm was employed. Practical implications: Stainless steel is one of the most popular materials used for selective laser sintering (SLM) processing to produce nearly fully dense components from 3D CAD models. Reduction of porosity is one of the critical research issues within the additive manufacturing technique SLM, since one of the major cost factors is the post-processing. Originality/value: This manuscript can serve as an aid in understanding the importance of technological parameters on quality and porosity of manufactured AM parts made by SLM technique.
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Merkt, Simon, Christian Hinke, Henrich Schleifenbaum, and Holger Voswinckel. "Integrative Technology Evaluation Model (ITEM) for Selective Laser Melting (SLM)." Advanced Materials Research 337 (September 2011): 274–80. http://dx.doi.org/10.4028/www.scientific.net/amr.337.274.
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This paper focuses on the evaluation of manufacturing processes that are competing with Selective Laser Melting (SLM). In 3D-part production of serial parts SLM is starting to be an economic choice for manufacturing. An integrated technology evaluation model (ITEM) is presented that helps decision makers to determine the potential of SLM while comparing with conventional manufacturing technologies. In contrast to conventional evaluation methodologies the ITEM considers interactions between product and process innovations generated by SLM. The paper closes with a technical and economical evaluation of a test part from Festo AG to validate two important parts of the ITEM.
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Ponnusamy, Panneer, Rizwan Abdul Rahman Rashid, Syed Hasan Masood, Dong Ruan, and Suresh Palanisamy. "Mechanical Properties of SLM-Printed Aluminium Alloys: A Review." Materials 13, no. 19 (September 26, 2020): 4301. http://dx.doi.org/10.3390/ma13194301.
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Selective laser melting (SLM) is a powder bed fusion type metal additive manufacturing process which is being applied to manufacture highly customised and value-added parts in biomedical, defence, aerospace, and automotive industries. Aluminium alloy is one of the widely used metals in manufacturing parts in SLM in these sectors due to its light weight, high strength, and corrosion resistance properties. Parts used in such applications can be subjected to severe dynamic loadings and high temperature conditions in service. It is important to understand the mechanical response of such products produced by SLM under different loading and operating conditions. This paper presents a comprehensive review of the latest research carried out in understanding the mechanical properties of aluminium alloys processed by SLM under static, dynamic, different build orientations, and heat treatment conditions with the aim of identifying research gaps and future research directions.
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Chen, Tian, Linzhi Wang, and Sheng Tan. "Effects of vacuum annealing treatment on microstructures and residual stress of AlSi10Mg parts produced by selective laser melting process." Modern Physics Letters B 30, no. 19 (July 20, 2016): 1650255. http://dx.doi.org/10.1142/s0217984916502559.
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Selective laser melting (SLM)-fabricated AlSi10Mg parts were heat-treated under vacuum to eliminate the residual stress. Microstructure evolutions and tensile properties of the SLM-fabricated parts before and after vacuum annealing treatment were studied. The results show that the crystalline structure of SLM-fabricated AlSi10Mg part was not modified after the vacuum annealing treatment. Additionally, the grain refinement had occurred after the vacuum annealing treatment. Moreover, with increasing of the vacuum annealing time, the second phase increased and transformed to spheroidization and coarsening. The SLM-produced parts after vacuum annealing at 300[Formula: see text]C for 2 h had the maximum ultimate tensile strength (UTS), yield strength (YS) and elongation, while the elastic modulus decreased significantly. In addition, the tensile residual stress was found in the as-fabricated AlSi10Mg samples by the microindentation method.
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Uhlmann, E., and V. Kashevko. "Oberflächengüte additiv gefertigter Kupferbauteile*/Surface quality of additive copper alloy parts – Investigations to increase the surface quality of top and side faces of SLM-generated CuCr1Zr copper alloy parts." wt Werkstattstechnik online 108, no. 11-12 (2018): 815–20. http://dx.doi.org/10.37544/1436-4980-2018-11-12-75.
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Das Laserstrahlschmelzen (SLM) als additives Fertigungsverfahren ist prädestiniert für die Herstellung von individuellen Bauteilen oder Werkzeugen mit hoher geometrischer Komplexität durch äußere und innenliegende Features in der Einzelstück- und Kleinserienfertigung. Allerdings ist die Oberflächengüte sowohl der Deck- als auch Seitenflächen von SLM-generierten Bauteilen nach dem Fertigungsprozess noch nicht zufriedenstellend, was für die Anwendung, etwa als Werkzeugeinsatz, von immenser Bedeutung ist. Daher ist die Verbesserung der Oberflächenbeschaffenheit von Kupferbauteilen der Schwerpunkt dieser Untersuchung. Selective Laser Melting (SLM) as an additive manufacturing process is well suited for the production of individual components or tools with high internal and external geometric complexity for individual parts and small batches. However, the quality of top and side surfaces of SLM parts is still unsatisfactory after the process. Therefore, this study focuses on the improvement of the surface quality on copper alloy parts.
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Fieger, Thiemo Valentin, Maximilian Ferdinand Sattler, and Gerd Witt. "Developing laser beam welding parameters for the assembly of steel SLM parts for the automotive industry." Rapid Prototyping Journal 24, no. 8 (November 12, 2018): 1288–95. http://dx.doi.org/10.1108/rpj-12-2016-0204.
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Purpose This paper aims to identify issues with joining selective laser melting (SLM) steels with conventional cold rolled steels through remote laser beam welding. Design/methodology/approach A novel approach for substituting conventional cold rolled metal sheets with SLM metal sheets, made of 316L and 18-Ni 300, is presented. The characteristics of the interaction of wrought and SLM materials are described, and joining benchmark parameters are presented and compared to known existing joining results. Finally, the joints are assessed in line with automotive specifications. This research also addresses the importance of joining technologies for the implementation of SLM as a full-fledged manufacturing technology for the automotive industry. Findings New parameter ranges for laser beam welding of SLM steels are defined. Research limitations/implications This research is limited to the examined steels and the used machines, parameters and equipment. Practical implications The presented benchmark parameters are expected to be useful for designers, product developers and machine operators. Originality/value Little knowledge is available about the behavior of SLM materials and their suitability for assembly processes. Novel information about SLM steels and their interaction with conventionally produced steel sheets is presented.
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Maamoun, Ahmed, Yi Xue, Mohamed Elbestawi, and Stephen Veldhuis. "The Effect of Selective Laser Melting Process Parameters on the Microstructure and Mechanical Properties of Al6061 and AlSi10Mg Alloys." Materials 12, no. 1 (December 20, 2018): 12. http://dx.doi.org/10.3390/ma12010012.
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Additive manufacturing (AM) offers customization of the microstructures and mechanical properties of fabricated components according to the material selected and process parameters applied. Selective laser melting (SLM) is a commonly-used technique for processing high strength aluminum alloys. The selection of SLM process parameters could control the microstructure of parts and their mechanical properties. However, the process parameters limit and defects obtained inside the as-built parts present obstacles to customized part production. This study investigates the influence of SLM process parameters on the quality of as-built Al6061 and AlSi10Mg parts according to the mutual connection between the microstructure characteristics and mechanical properties. The microstructure of both materials was characterized for different parts processed over a wide range of SLM process parameters. The optimized SLM parameters were investigated to eliminate internal microstructure defects. The behavior of the mechanical properties of parts was presented through regression models generated from the design of experiment (DOE) analysis for the results of hardness, ultimate tensile strength, and yield strength. A comparison between the results obtained and those reported in the literature is presented to illustrate the influence of process parameters, build environment, and powder characteristics on the quality of parts produced. The results obtained from this study could help to customize the part’s quality by satisfying their design requirements in addition to reducing as-built defects which, in turn, would reduce the amount of the post-processing needed.
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Yan, Xiaoling, Jincheng Pang, and Yanlong Jing. "Ultrasonic Measurement of Stress in SLM 316L Stainless Steel Forming Parts Manufactured Using Different Scanning Strategies." Materials 12, no. 17 (August 25, 2019): 2719. http://dx.doi.org/10.3390/ma12172719.
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Selective Laser Melting (SLM) technology is a new kind of additive manufacturing technology developed in in the last decade. Measurement and control of stress in metal forming layer is the basic problem of SLM forming parts. Critical Refraction Longitudinal (LCR) wave method was used to measure stress. The acoustic-elastic formulas for measuring stresses in SLM 316L stainless steel forming parts manufactured using meander, stripe, and chess board scanning strategies, respectively, were established based on static load tensile test. The experimental results show that the acoustic time difference of LCR wave in SLM specimen manufactured with 316L stainless steel increases linearly with the increase of stress when the tensile stress is less than critical stress (372 MPa, 465 MPa, and 494 MPa). Due to the inhomogeneous deformation of the anisotropic SLM forming layer and the dimple-micropore aggregation fracture mechanism, the acousto-elastic curve fluctuates up and down along the irregular curve when the tensile stress is larger than critical stress. The results of corroboration experiments show that nondestructive measurement of stress in SLM forming specimen can be realized by using LCR wave method. The scanning strategy can significantly affect the tensile strength and yield strength of SLM forming specimen. The stresses were all in tension stress state at the edge of the specimens, whatever scanning strategy was used. Sub-area scanning and scanning sequence of alternate and intersect were adopted, which can effectively reduce the stress in the SLM forming specimen. The overall stress values of SLM forming specimen manufactured using chess board scanning strategy were smaller than that using meander and stripe strategies. The distribution of stress were more uniform.
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Maamoun, Ahmed, Yi Xue, Mohamed Elbestawi, and Stephen Veldhuis. "Effect of Selective Laser Melting Process Parameters on the Quality of Al Alloy Parts: Powder Characterization, Density, Surface Roughness, and Dimensional Accuracy." Materials 11, no. 12 (November 22, 2018): 2343. http://dx.doi.org/10.3390/ma11122343.
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Additive manufacturing (AM) of high-strength Al alloys promises to enhance the performance of critical components related to various aerospace and automotive applications. The key advantage of AM is its ability to generate lightweight, robust, and complex shapes. However, the characteristics of the as-built parts may represent an obstacle to the satisfaction of the parts’ quality requirements. The current study investigates the influence of selective laser melting (SLM) process parameters on the quality of parts fabricated from different Al alloys. A design of experiment (DOE) was used to analyze relative density, porosity, surface roughness, and dimensional accuracy according to the interaction effect between the SLM process parameters. The results show a range of energy densities and SLM process parameters for AlSi10Mg and Al6061 alloys needed to achieve “optimum” values for each performance characteristic. A process map was developed for each material by combining the optimized range of SLM process parameters for each characteristic to ensure good quality of the as-built parts. This study is also aimed at reducing the amount of post-processing needed according to the optimal processing window detected.
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Konečná, Radomila, and Gianni Nicoletto. "Near-Surface Structure and Fatigue Crack Initiation Mechanisms of As-Built SLM Inconel 718." Defect and Diffusion Forum 405 (November 2020): 306–11. http://dx.doi.org/10.4028/www.scientific.net/ddf.405.306.
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Challenging structural applications such as customized jet engine parts are increasingly fabricated by Selective Laser Melting (SLM) of Inconel 718 powder. The as-built surface quality of SLM parts is however inferior of the machined version and the fatigue behavior is negatively affected. The as-built fatigue response of SLM Inconel 718 was quantified here using three sets of directional specimens. Since the surface quality is influenced by powder characteristics, process parameters and layer-wise fabrication, fatigue results showed a directional contribution that was interpreted using metallography and fractography.
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Bassani, Paola, Carlo Alberto Biffi, Riccardo Casati, Adrianni Zanatta Alarcon, Ausonio Tuissi, and Maurizio Vedani. "Properties of Aluminium Alloys Produced by Selective Laser Melting." Key Engineering Materials 710 (September 2016): 83–88. http://dx.doi.org/10.4028/www.scientific.net/kem.710.83.
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Analysis of peculiar properties offered by Al alloys produced according to additive manufacturing techniques, specifically by Selective Laser Melting (SLM), is carried out. Two alloys are considered, derived by casting (AlSi10Mg) and by wrought (ENAW 2618) applications. The SLM processed samples are investigated considering their microstructural and mechanical properties after SLM and compared to cast and wrought counterparts. A strong microstructural refinement induced by SLM processing is observed for both alloys, resulting in excellent hardness properties. Investigation on integrity of samples revealed that small-size microvoids and unmelted regions could be present in SLM parts.
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Liu, Jin Hui, Wen Juan Xie, Qing Song Wei, and Li Wang. "Progress on Investigation of Pores During Selective Laser Melting of Metal Powders and Future Work Discussion." Advanced Materials Research 291-294 (July 2011): 3088–94. http://dx.doi.org/10.4028/www.scientific.net/amr.291-294.3088.
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Pores are always considered as a kind of defect during manufacturing metal parts via many conventional processes. But porous metals have outstanding physical and mechanical properties which providing them double natures of function and structure, and are applied in many fields of science and technology. Selective laser melting (SLM), developed within current years, has the advantages of producing metal parts with complex structures, and can be used to manufacture complex structures of any kind theoretically. A new method of making porous complicated metal structures via SLM is put forward. Then, the meaning of this method, research advance and future work discussion are presented in this paper, which lays a method foundation for future study and build a new field for both porous metal parts and SLM technology.
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Cloots, Michael, Livia Zumofen, Adriaan Bernardus Spierings, Andreas Kirchheim, and Konrad Wegener. "Approaches to minimize overhang angles of SLM parts." Rapid Prototyping Journal 23, no. 2 (March 20, 2017): 362–69. http://dx.doi.org/10.1108/rpj-05-2015-0061.
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Purpose For geometries exhibiting overhanging surfaces, support structures are needed to dissipate process heat and to minimize geometrical distortions attributed to internal stresses. The use of support structures is often time- and cost-consuming. For this reason, this study aims to propose an approach which minimizes the use of such structures. Design/methodology/approach For minimizing the use of support structures, process parameters in combination with a contour-like exposure strategy are developed to realize support-less overhanging structures of less than 35°. These parameters are implemented in a shell-core strategy, which follows the idea of applying different processing strategies to the critical (overhanging) shell and the uncritical core of the part. Thereby, the core is processed with standard parameters, aiming a dense material. On the critical shell, optimized processing parameters are applied, reaching good results in terms of surface quality, especially at extreme overhang situations. Findings The results show that the selective laser melting (SLM) technology is able to realize support-less overhanging surfaces by choosing suitable scan strategies and process parameters. Particularly good results are always obtained when the exposure direction of the shell is parallel to the contour of the sample. Originality/value The validity of the results is demonstrated through the successful reproduction of the build strategy on two commercial SLM machines, reaching support-free builds of surfaces with an angle to the horizontal of less than or equal to 30°.
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Al-Rubaie, Kassim S., Saulo Melotti, Alexsandro Rabelo, José M. Paiva, Mohamed A. Elbestawi, and Stephen C. Veldhuis. "Machinability of SLM-produced Ti6Al4V titanium alloy parts." Journal of Manufacturing Processes 57 (September 2020): 768–86. http://dx.doi.org/10.1016/j.jmapro.2020.07.035.
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Maksimov, Peter, Oleg Smetannıkov, Aleksandra Dubrovskaya, Konstantin Dongauzer, and Leonid Bushuev. "Numeric simulation of aircraft engine parts additive manufacturing process." MATEC Web of Conferences 224 (2018): 01065. http://dx.doi.org/10.1051/matecconf/201822401065.
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This paper presents the results of software (ANSYS software) improvements specific for modeling the physical process of SLM (Selective Laser Melting). Improvement goal was to create a set of mathematical models and user environment (a set of APDL programs) based on the ANSYS finite element analysis system solver, allowing to perform the technological procedure of physical SLM process numerical modeling to the required degree of precision with an estimate of the final distortion and residual stresses of gas turbine engine parts to optimize the manufacturing process.
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Deng, Yong, Zhongfa Mao, Nan Yang, Xiaodong Niu, and Xiangdong Lu. "Collaborative Optimization of Density and Surface Roughness of 316L Stainless Steel in Selective Laser Melting." Materials 13, no. 7 (April 1, 2020): 1601. http://dx.doi.org/10.3390/ma13071601.
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Although the concept of additive manufacturing has been proposed for several decades, momentum in the area of selective laser melting (SLM) is finally starting to build. In SLM, density and surface roughness, as the important quality indexes of SLMed parts, are dependent on the processing parameters. However, there are few studies on their collaborative optimization during SLM to obtain high relative density and low surface roughness simultaneously in the literature. In this work, the response surface method was adopted to study the influences of different processing parameters (laser power, scanning speed and hatch space) on density and surface roughness of 316L stainless steel parts fabricated by SLM. A statistical relationship model between processing parameters and manufacturing quality is established. A multi-objective collaborative optimization strategy considering both density and surface roughness is proposed. The experimental results show that the main effects of processing parameters on the density and surface roughness are similar. We observed that the laser power and scanning speed significantly affected the above objective quality, but the influence of the hatch spacing was comparatively low. Based on the above optimization, 316L stainless steel parts with excellent surface roughness and relative density can be obtained by SLM with optimized processing parameters.
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Zhang, L. C., and T. B. Sercombe. "Selective Laser Melting of Low-Modulus Biomedical Ti-24Nb-4Zr-8Sn Alloy: Effect of Laser Point Distance." Key Engineering Materials 520 (August 2012): 226–33. http://dx.doi.org/10.4028/www.scientific.net/kem.520.226.
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As many complex processing parameters are involved in Selective Laser Melting (SLM), an understanding of the scientific and technical aspects of the production route on the microstructural evolution during SLM process is required in order to obtain parts with near full density and desirable surface finish. Although the effects of the various processing parameters on the density of parts have been well documented, the effect of laser point distance on density and mechanical properties of the SLM-produced parts has not been widely studied. In this paper, we present the results of using SLM to produce biomedical beta Ti-24Nb-4Zr-8Sn components. Both the density and hardness of the material increases with increasing incident laser energy and reaches a near full density value of >99% without any post-processing. When the laser energy density input is high enough to fully melt powder, the laser point distance has no influence on the density or hardness of the samples. In contrast, at low energy densities, large point distances have been shown to be detrimental.
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Leal, Malena Ley Bun, Barbara Bermudez-Reyes, Patricia del Carmen Zambrano Robledo, and Omar Lopez-Botello. "Parameter optimization of aluminum alloy thin structures obtained by Selective Laser Melting." MRS Advances 4, no. 55-56 (2019): 2997–3005. http://dx.doi.org/10.1557/adv.2019.434.
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ABSTRACTSelective Laser Melting (SLM) involves numerous fabrication parameters, the interaction between those parameters determine the final characteristics of the resulting part and because of the latter, it is considered a complex process. Low-density components is one of the main issues of the SLM process, due to the incorrect selection of process parameters. These defects are undesired in high specialized applications (i.e. aerospace, aeronautic and medical industries). Therefore, the characterization of the defects (pores) found in aluminum parts manufacture by SLM and the relationship with fabrication parameters was performed. A robust orthogonal design of experiments was implemented to determine process parameters, and then parts were manufactured in SLM. Relative density of the samples was then characterized using the Archimedes principle and microscopy; the data was then statistically analyzed in order to determine the optimal process parameters. The main purpose of the present research was to establish the best processing parameters of an in-house SLM system, as well as to characterize the pore geometry in order to fully eliminate pores in a future research.
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Jadhav, Dadbakhsh, Vleugels, Hofkens, Puyvelde, Yang, Kruth, Humbeeck, and Vanmeensel. "Influence of Carbon Nanoparticle Addition (and Impurities) on Selective Laser Melting of Pure Copper." Materials 12, no. 15 (August 2, 2019): 2469. http://dx.doi.org/10.3390/ma12152469.
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The addition of 0.1 wt % carbon nanoparticles significantly improved the optical absorption and flowability of gas-atomized copper powder. This facilitated selective laser melting (SLM) by reducing the required laser energy density to obtain 98% dense parts. Moreover, the carbon addition led to an in situ de-oxidation of the copper parts during the SLM process. The properties of the as-built copper parts were limited to a tensile strength of 125 MPa, a ductility of 3%, and an electrical conductivity of 22.7 × 106 S/m, despite the advantageous effect of carbon on the powder characteristics and SLM behavior. The modest mechanical properties were associated with the segregation of carbon nanoparticles and other impurities, such as phosphorus and oxygen along grain boundaries of epitaxially grown grains. Whereas, the low electrical conductivity was mainly attributed to the phosphorus impurity in solid-solution with copper.
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Gong, Haijun, Venkata Karthik Nadimpalli, Khalid Rafi, Thomas Starr, and Brent Stucker. "Micro-CT Evaluation of Defects in Ti-6Al-4V Parts Fabricated by Metal Additive Manufacturing." Technologies 7, no. 2 (June 12, 2019): 44. http://dx.doi.org/10.3390/technologies7020044.
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In this study, micro-computed tomography (CT) is utilized to detect defects of Ti-6Al-4V specimens fabricated by selective laser melting (SLM) and electron beam melting (EBM), which are two popular metal additive manufacturing methods. SLM and EBM specimens were fabricated with random defects at a specific porosity. The capability of micro-CT to evaluate inclusion defects in the SLM and EBM specimens is discussed. The porosity of EBM specimens was analyzed through image processing of CT single slices. An empirical method is also proposed to estimate the porosity of reconstructed models of the CT scan.
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Li, Zhonghua, Ibrahim Kucukkoc, David Z. Zhang, and Fei Liu. "Optimising the process parameters of selective laser melting for the fabrication of Ti6Al4V alloy." Rapid Prototyping Journal 24, no. 1 (January 2, 2018): 150–59. http://dx.doi.org/10.1108/rpj-03-2016-0045.
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Purpose Surface roughness is an important evaluation index for industrial components, and it strongly depends on the processing parameters for selective laser molten Ti6Al4V parts. This paper aims to obtain an optimum selective laser melting (SLM) parameter set to improve the surface roughness of Ti6Al4V samples. Design/methodology/approach A response surface methodology (RSM)-based approach is proposed to improve the surface quality of selective laser molten Ti6Al4V parts and understand the relationship between the SLM process parameters and the surface roughness. The main SLM parameters (i.e. laser power, scan speed and hatch spacing) are optimized, and Ti6Al4V parts are manufactured by the SLM technology with no post processes. Findings Optimum process parameters were obtained using the RSM method to minimise the roughness of the top and vertical side surfaces. Obtained parameter sets were evaluated based on their productivity and surface quality performance. The validation tests have been performed, and the results verified the effectivity of the proposed technique. It was also shown that the top and vertical sides must be handled together to obtain better top surface quality. Practical implications The obtained optimum SLM parameter set can be used in the manufacturing of Ti6Al4V components with high surface roughness requirement. Originality/value RSM is used to analyse and determine the optimal combination of SLM parameters with the aim of improving the surface roughness quality of Ti6Al4V components, for the first time in the literature. Also, this is the first study which aims to simultaneously optimise the surface quality of top and vertical sides of titanium alloys.
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Pacurar, Razvan, and Petru Berce. "Research on How Lens Position of the Optical System is Influencing the Mechanical Characteristics of the Metallic Parts Made by Selective Laser Melting Equipment." Advanced Engineering Forum 8-9 (June 2013): 285–92. http://dx.doi.org/10.4028/www.scientific.net/aef.8-9.285.
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The Selective Laser Melting (SLM) is one of the most important Additive Manufacturing (AM) technologies that have been developed in the last few years, with applications in different domains, starting with the industrial engineering and ending with biomedical industry, as well. According to the type of the application (industrial or medical), the challenges and requirements related to this modern technology are different, regarding the mechanical properties of the manufactured parts. The article presents the theoretical and experimental research that was made by the authors in order to improve the mechanical characteristics of the metallic parts manufactured by using the Selective Laser Melting (SLM) technology. Finite element analysis method has been successfully used in order to study the connection between the density of the material and the fracture strength of several samples that were manufactured from Stainless Steel 316L material, at the Technical University of Cluj-Napoca, using the MCP Realizer II SLM 250 equipment. The experimental results that have been obtained by the authors have finally proved that there is a very strong connection between the lens position of the optical system and the resulted porosity of the parts manufactured by using the SLM machine.
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Baitimerov, R. M. "Single Track Formation during Selective Laser Melting of Ti-6Al-4V Alloy." Materials Science Forum 946 (February 2019): 978–83. http://dx.doi.org/10.4028/www.scientific.net/msf.946.978.
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Selective laser melting (SLM) is an additive manufacturing technology that allows to produce functional parts with extremely complex shape from metal powder feedstock. 240 single tracks with the length of 10 mm were fabricated using different SLM process parameters: laser power output, powder layer thickness, point distance and exposure time. Obtained single tracks were measured using optical microscopy. An influence of SLM process parameters on geometrical characteristics of obtained single tracks was investigated.
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Zhao, Zhanyong, Liang Li, Le Tan, Peikang Bai, Jing Li, Liyun Wu, Haihong Liao, and Yahui Cheng. "Simulation of Stress Field during the Selective Laser Melting Process of the Nickel-Based Superalloy, GH4169." Materials 11, no. 9 (August 24, 2018): 1525. http://dx.doi.org/10.3390/ma11091525.
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In this paper, GH4169 alloy’s distributions of temperature and stress during the selective laser melting (SLM) process were studied. The SLM process is a dynamic process of rapid melting and solidification, and we found there were larger temperature gradients near the turning of scan direction and at the overlap of the scanning line, which produced thermal strain and stress concentration and gave rise to warping deformations. The stresses increased as the distance became further away from the melt pool. There was tensile stress in the most-forming zones, but compressive stress occurred near the melt pool area. When the parts were cooled to room temperature after the SLM process, tensile stress was concentrated around the parts’ boundaries. Residual stress along the z direction caused the warping deformations, and although there was tensile stress in the parts’ surfaces, but there was compressive stress near the substrate.
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Hötter, Jan Steffen, Miranda Fateri, and Andreas Gebhardt. "Selective Laser Melting of Metals: Desktop Machines Open up New Chances even for Small Companies." Advanced Materials Research 622-623 (December 2012): 461–65. http://dx.doi.org/10.4028/www.scientific.net/amr.622-623.461.
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Additive manufacturing (AM) of metal parts by using Selective Laser Melting (SLM) has become a powerful tool mostly in the area of automotive, aerospace engineering and others. Especially in the field of dentistry, jewelry and related branches that require individualized or even one-of-a-kind products, the direct digital manufacturing process opens up new ways of design and manufacturing. In these fields, mostly small and medium sized businesses (SME) are operating which do not have sufficient human and economic resources to invest in this technology. But to stay competitive, the application of AM can be regarded as a necessity. In this situation a new desktop machine (Realizer SLM 50) was introduced that cost about 1/3 of a shop floor SLM machine and promises small quality parts. To find out whether the machine really is an alternative for SMEs the University of Applied Science, Aachen, Germany, designed, build and optimized typical parts from the dentistry and the jewelry branches using CoCr and silver material, the latter being new with this application. The paper describes the SLM procedure and how to find and optimize the most important parameters. The test is accompanied by digital simulation in order to verify the build parameters and to plan future builds. The procedure is shown as well as the resulting parts made from CoCr and silver material.
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Yadroitsava, Ina, Stephen Grewar, Daniel Hattingh, and Igor Yadroitsev. "Residual Stress in SLM Ti6Al4V Alloy Specimens." Materials Science Forum 828-829 (August 2015): 305–10. http://dx.doi.org/10.4028/www.scientific.net/msf.828-829.305.
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Selective Laser Melting (SLM) presents a modern manufacturing process with an innovative technology which allows the production of full-density objects or fine-structured parts with complex geometry and inner structures. Stability and certification of the properties of SLM parts are important tasks for all producers and end-users. One of the drawbacks of this technology is high residual stress in as-made SLM objects. In this study X-ray diffraction technique was used for investigating the residual stress induced into SLM Ti6Al4V alloy samples. Principal stresses were estimated for the cut rectangular specimen. Two types of the cantilevers were produced and numerical simulation of the stress was performed. The bending of cut cantilevers was measured before and after heat treatment. Next series of the samples had rectangular shapes and different thicknesses from 1 to 46 layers. All as-manufactured specimens attached to the substrate showed the presence of tensile residual stresses near the top surface. Residual stress along the laser scanning direction had magnitudes twice that of the stress in the perpendicular direction. Conclusions regarding directions and values of stresses in SLM objects from Ti6Al4V powder are given.
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Buican, George Răzvan, Gheorghe Oancea, Camil Lancea, and Mihai Alin Pop. "Influence of Layer Thickness on Internal Structure of Parts Manufactured from 316-L Steel Using SLM Technology." Applied Mechanics and Materials 809-810 (November 2015): 369–74. http://dx.doi.org/10.4028/www.scientific.net/amm.809-810.369.
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Nowadays Additive Manufacturing, and in particular Selective Laser Melting (SLM ), is being used more and more. The SLM manufacturing process has been subjects to a lot of studies in order to improve the manufacturing parameters. In this paper are presented some researches on the internal structure of the manufactured parts with two layer thickness: 30[μm] and 50[μm]. The internal structure of parts manufactured on SLM machine is obtained as images with a microscope. On the images each grain of the internal structures is painted in a different color and grouped according to its shape. All data about grains are analyzed by the means of statistical methods. The two manufacturing strategies, 30[μm] and 50[μm] layer thickness, generate parts that have slightly different internal structures. Thus, from the point of views of internal structure and manufacturing time, the strategy with 50[μm] layer thickness can be used because it generates a lowering in manufacturing costs and increases the overall productivity.
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Boschetto, Alberto, Luana Bottini, Luciano Macera, and Francesco Veniali. "Post-Processing of Complex SLM Parts by Barrel Finishing." Applied Sciences 10, no. 4 (February 19, 2020): 1382. http://dx.doi.org/10.3390/app10041382.
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Selective laser melting (SLM) enables the production of metal complex shapes that are difficult or impossible to obtain with conventional production processes. However, the attainable surface quality is insufficient for most applications; thus, a secondary finishing is frequently required. Barrel finishing is an interesting candidate but is often applied without consistent criteria aimed at finding processing parameters. This work presents a methodology based on Bagnold number evaluation and bed behavior diagram, developed on experimental apparatus with different charges and process parameters. The experimentation on an industrial machine and the profilometric analysis allowed the identification of appropriate process parameters and charge media for finishing the investigated materials (Ti6Al4V and Inconel718). Two case studies, characterized by complex shapes, were considered, and consistent surface measures allowed understanding the capability of the technology.
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Li, Rui Di, Yu Sheng Shi, Zhi Gang Wang, and Jin Hui Liu. "Selective Laser Melting of Multi-Component Ni-Based Powder Mixture for Building Metallic Parts." Materials Science Forum 675-677 (February 2011): 723–26. http://dx.doi.org/10.4028/www.scientific.net/msf.675-677.723.
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Selective laser melting (SLM) is an advanced manufacturing technology, which is flexible in building three-dimensional (3D) metallic parts. In this work, SLM experiment of a multicomponent Ni-based composite powder, which consisted of Ni, Cr, Fe, and Al powders, was conducted with favorable forming ability. The SEM, EDX, and XRD analysis were used to characterize the surface morphology, microstructure, and phase structure of as-formed Ni-based alloy. The XRD analysis showed that the as-received phase structure was Ni based solid solution. The SEM analysis of surface morphology revealed that metal agglomerates or balls were very easily formed in SLM surface, between which some pore channels existed. The surface condition and porosity could be improved by increasing laser energy input, because of a higher molten temperature and accordingly better flowing and flatting characteristics. The SEM analysis of microstructure showed that the crystalline grains were in cellular and columnar shape. Moreover, the grains were very fine with average dimensions about 5μm, due to the rapid cooling rate with rapid laser beam moving. The EDX analysis illustrated that the element contents of starting powder were uniformly distributed in as-prepared sample. A case investigation into SLM of this composite powder to form an impeller was also performed.
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Khan, Mushtaq, and Phill Dickens. "Selective laser melting (SLM) of pure gold for manufacturing dental crowns." Rapid Prototyping Journal 20, no. 6 (October 20, 2014): 471–79. http://dx.doi.org/10.1108/rpj-03-2013-0034.
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Purpose – This paper aims to present the application aspect of the work to manufacturing premolar and molar dental crowns by selective laser melting (SLM) of pure gold. Over the years different metals have been processed using laser-based Additive Manufacturing processes, but very little work has been published on the SLM of gold (Au). Previously published work presented suitable processing parameters for SLM of pure gold. Design/methodology/approach – Suitable processing parameters were used to manufacture premolar and molar dental crowns using SLM system. Different layer thickness was used to analyse the effect on surface quality of crowns. Mechanical properties are checked using nanoindentation and micro Computerized Tomography scanning. Findings – Dental crowns were successfully manufacturing using new build platform and suitable processing parameters. Parts were manufacturing using minimal supports which prevented parts from damaging during removal. A bed temperature of 100°C was found suitable for reducing warpage in the layers. Layer thickness of 50μm was found to have better surface quality and structural integrity as compared to 75μm. Porosity was found to be predominantly inter-layer. Small difference in mechanical properties of dental crowns is associated with the laser processing. Originality/value – This research is the first of its kind which presents dental crown manufacturing using SLM of pure gold.
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Yap, Chor Yen, Hongyi Kenneth Tan, Zhenglin Du, Chee Kai Chua, and Zhili Dong. "Selective laser melting of nickel powder." Rapid Prototyping Journal 23, no. 4 (June 20, 2017): 750–57. http://dx.doi.org/10.1108/rpj-01-2016-0006.
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Purpose Selective laser melting (SLM) is an additive manufacturing technology that is gaining industrial and research interest as it can directly fabricate near full density metallic components. The paper aims to identify suitable process parameters for SLM of processing of pure nickel powder and to study the microstructure of such products. The study also aims to characterize the microhardness and tensile properties of pure nickel produced by SLM. Design/methodology/approach A 24 factorial design experiment was carried out to identify the most significant factors on the resultant porosity of nickel parts. A subsequent experiment was carried out with a laser power of 350 W. The scanning speeds and hatch spacings were varied. Findings Scanning speed and hatch spacing have significant effects on the porosity of SLM components. A high relative density of 98.9 per cent was achieved, and microhardness of 140 to 160 Hv was obtained from these samples. A tensile strength 452 MPa was obtained. Research limitations/implications As the energy input levels were made in steps of 20 J/mm3 for the optimization study, the true optimal combination of parameters may have been missed. Therefore, researchers are encouraged to test the parameters with smaller variations in energy levels. Practical implications The paper provides a set of optimized parameters for the SLM of pure nickel. This study enables the three-dimensional (3D) printing of objects with nickel, which has applications in chemical catalyses and in microelectromechanical systems with its magnetostrictive properties. Originality value This research is the first in direct processing of pure nickel using SLM, with the identification of suitable process parameters. The study also provides an understanding of the porosity, microhardness, strength and microstructure of SLM produced nickel parts. This work paves the way for standardization of 3D printed nickel components and enables the applications of pure nickel via SLM.
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Giganto, Sara, Susana Martínez-Pellitero, Eduardo Cuesta, Víctor M. Meana, and Joaquín Barreiro. "Analysis of Modern Optical Inspection Systems for Parts Manufactured by Selective Laser Melting." Sensors 20, no. 11 (June 4, 2020): 3202. http://dx.doi.org/10.3390/s20113202.
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Metal additive manufacturing (AM) allows obtaining functional parts with the possibility of optimizing them topologically without affecting system performance. This is of great interest for sectors such as aerospace, automotive, and medical–surgical. However, from a metrological point of view, the high requirements applied in these sectors constitute a challenge for inspecting these types of parts. Non-contact inspection has gained great relevance due to the rapid verification of AM parts. Optical measurement systems (OMSs) are being increasingly adopted for geometric dimensioning and tolerancing (GD&T) verification within the context of Industry 4.0. In this paper, the suitability (advantages and limitations) of five different OMSs (based on laser triangulation, conoscopic holography, and structured light techniques) for GD&T verification of parts manufactured by selective laser melting (SLM) is analyzed. For this purpose, a specific testing part was designed and SLM-manufactured in 17-4PH stainless steel. Once the part was measured by contact (obtaining the reference GD&T values), it was optically measured. The scanning results allow comparing the OMSs in terms of their inspection speed as well as dimensional and geometrical accuracy. As a result, two portable systems (handheld laser triangulation and structured blue-light scanners) were identified as the most accurate optical techniques for scanning SLM parts.
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Dadbakhsh, Sasan, and Liang Hao. "Effect of Layer Thickness in Selective Laser Melting on Microstructure of Al/5 wt.%Fe2O3Powder Consolidated Parts." Scientific World Journal 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/106129.
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In situreaction was activated in the powder mixture of Al/5 wt.%Fe2O3by using selective laser melting (SLM) to directly fabricate aluminium metal matrix composite parts. The microstructural characteristics of thesein situconsolidated parts through SLM were investigated under the influence of thick powder bed, 75 μm layer thickness, and 50 μm layer thickness in various laser powers and scanning speeds. It was found that the layer thickness has a strong influence on microstructural outcome, mainly attributed to its impact on oxygen content of the matrix. Various microstructural features (such as granular, coralline-like, and particulate appearance) were observed depending on the layer thickness, laser power, and scanning speed. This was associated with various material combinations such as pure Al, Al-Fe intermetallics, and Al(-Fe) oxide phases formed afterin situreaction and laser rapid solidification. Uniformly distributed very fine particles could be consolidated in net-shape Al composite parts by using lower layer thickness, higher laser power, and lower scanning speed. The findings contribute to the new development of advanced net-shape manufacture of Al composites by combining SLM andin situreaction process.
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Hao, Xinxin, Xiaoxue Li, and Jingchen Zheng. "Screening China Emergency Medical Team (CEMT) Members: A Self-Leadership Perspective." Prehospital and Disaster Medicine 33, no. 6 (October 31, 2018): 596–601. http://dx.doi.org/10.1017/s1049023x18000961.
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AbstractObjectiveThis study aims at establishing the self-leadership development model (SLM) of China Emergency Medical Team (CEMT) members as a supplement to current selection standards of CEMT members.MethodsRaw dataset was obtained through two ways: in-depth interviews and documentary materials (memoirs and articles). The in-depth interviews were conducted with a purposive sample of 12 CEMT members, all of whom have participated in multiple disaster relief activities and have been CEMT members for more than two years. This paper followed a grounded theory methodology dealing with all data.ResultsBased on tasks, the SLM-CEMT consists of three basic parts: (1) making plans; (2) action; and (3) outcomes. Different parts involve various self-leadership strategies, of which five are the original dimensions of previous research (goal-setting, visualizing successful performance, self-talk, self-reward, and self-correcting feedback) and three are new dimensions (role clarity, self-initiative, and self-vigilance).Conclusions:The SLM-CEMT, with the three new parts, provides a new look at screening CEMT members as well as pondering on future research. Based on the SLM-CEMT, administrators could screen more qualified CEMT members. For the limitations, future work will be on the generalization and confirmation of this model.HaoX,LiX,ZhengJ.Screening China Emergency Medical Team (CEMT) members: a self-leadership perspective.Prehosp Disaster Med.2018;33(6):596–601.
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Buican, George Răzvan, Gheorghe Oancea, and Alexandru Manolescu. "Remanufacturing of Damaged Parts Using Selective Laser Melting Technology." Applied Mechanics and Materials 693 (December 2014): 285–90. http://dx.doi.org/10.4028/www.scientific.net/amm.693.285.
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This paper presents the stages taken to remanufacture a damaged part, for which no documentation is available, using the SLM additive technologies. A damaged part is scanned using the COMET L3D scanner and the points cloud is used to redesign and reconstruct the part as a 3D CAD model. Using the generated 3D CAD model the build job for the SLM is created by designing and adding the construction supports, the material type and the type of hatching strategy for each slice. The slices are used by the SLM250HL equipment and the new metallic part is manufactured. The manufactured part was scanned with the same 3D scanner and the data from the original part was compared with the new reading. The results can be used to reconstruct more complex parts, to redesign the broken parts and to improve the manufacturing process.
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Gudushauri, �. G., and G. Ya Panovko. "Assembly of parts with guaranteed tightness under vibrational conditions." Strength of Materials 18, no. 2 (February 1986): 221–24. http://dx.doi.org/10.1007/bf01522560.
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Hassanin, Hany, Khamis Essa, Chunlei Qiu, Ali M. Abdelhafeez, Nicholas J. E. Adkins, and Moataz M. Attallah. "Net-shape manufacturing using hybrid selective laser melting/hot isostatic pressing." Rapid Prototyping Journal 23, no. 4 (June 20, 2017): 720–26. http://dx.doi.org/10.1108/rpj-02-2016-0019.
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Purpose The purpose of this study is to develop a manufacturing technology using hybrid selective laser melting/hot isostatic pressing (SLM/HIP) process to produce full density net-shape components more rapidly and at lower cost than processing by SLM alone. Design/methodology/approach Ti-6Al-4V powder was encapsulated in situ by the production of as-SLMed shell prior to the HIP process. After HIPping, the SLM shell is an integral part of the final component. Finite element (FE) modelling based on pure plasticity theory of porous metal coupled with an iterative procedure has been adopted to simulate HIPping of the encapsulated Ti-6Al-4V powder and SLMed shell. Two demonstrator parts have been modelled, designed, produced and experimentally validated. Geometrical analysis and microstructural characterisation have been carried out to demonstrate the efficiency of the process. Findings The FE model is in agreement with the measured data obtained and confirms that the design of the shell affects the resulting deformed parts. In addition, the scanning electron microscope (SEM) and Electron backscatter diffraction EBSD (EBSD) of the interior and exterior parts reveal a considerably different grain structure and crystallographic orientation with a good bonding between the SLMed shell and HIPped powder. Originality/value An approach to improve SLM productivity by combining it with HIP is developed to further innovate the advanced manufacturing field. The possibility of the hybrid SLS/HIP supported by FEA simulation as a net shape manufacturing process for fabrication of high performance parts has been demonstrated.
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He, Ketai, and Xue Zhao. "3D Thermal Finite Element Analysis of the SLM 316L Parts with Microstructural Correlations." Complexity 2018 (October 3, 2018): 1–13. http://dx.doi.org/10.1155/2018/6910187.
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In this study, a multitrack and multilayer finite element model was developed to simulate the temperature field and molten pool contours during selective laser melting (SLM) of 316L stainless steel powder under different scanning strategies. The simulated temperature field and its evolution over time were compared with experimental measurement results. Furthermore, a correlation was established by the presented results between the predicted thermal behavior and the microstructure of SLM specimens. It was found that the maximum temperature of the molten pool rose slightly with the increase of scanning tracks, but when laser scanned multilayer, the maximum temperature rose first and then decreased. There are large columnar crystals in molten pools, growing in the direction of the maximum temperature gradient. The microstructure defects are more likely to occur at the bonding regions between adjacent layers and islands, where the heat and stress are concentrated. Moreover, the results also showed that the scanning strategy affects the microstructure and microhardness. Also, the SLM 316L parts under the S-shaped strategy had finer grains and a higher Vicker hardness than that formed under the island strategy.
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Santos, Luis, Joel de Jesus, José Ferreira, José Costa, and Carlos Capela. "Fracture Toughness of Hybrid Components with Selective Laser Melting 18Ni300 Steel Parts." Applied Sciences 8, no. 10 (October 11, 2018): 1879. http://dx.doi.org/10.3390/app8101879.
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Selective Laser Melting (SLM) is currently one of the more advanced manufacturing and prototyping processes, allowing the 3D-printing of complex parts through the layer-by-layer deposition of powder materials melted by laser. This work concerns the study of the fracture toughness of maraging AISI 18Ni300 steel implants by SLM built over two different conventional steels, AISI H13 and AISI 420, ranging the scan rate between 200 mm/s and 400 mm/s. The SLM process creates an interface zone between the conventional steel and the laser melted implant in the final form of compact tension (CT) samples, where the hardness is higher than the 3D-printed material but lower than the conventional steel. Both fully 3D-printed series and 3D-printed implants series produced at 200 mm/s of scan rate showed higher fracture toughness than the other series built at 400 mm/s of scan rate due to a lower level of internal defects. An inexpressive variation of fracture toughness was observed between the implanted series with the same parameters. The crack growth path for all samples occurred in the limit of interface/3D-printed material zone and occurred between laser melted layers.
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Ravichander, Bharath Bhushan, Amirhesam Amerinatanzi, and Narges Shayesteh Moghaddam. "Study on the Effect of Powder-Bed Fusion Process Parameters on the Quality of as-Built IN718 Parts Using Response Surface Methodology." Metals 10, no. 9 (September 2, 2020): 1180. http://dx.doi.org/10.3390/met10091180.
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Inconel 718 (IN718) is a nickel-based superalloy which is widely used in aerospace, oil, and gas industries due to its outstanding mechanical properties at high temperatures, corrosion, fatigue resistance, and excellent weldability. Selective laser melting (SLM), one of the most used powder-bed based methods, is being extensively used to fabricate functional IN718 components with high accuracy. The accuracy and the properties of the SLM fabricated IN718 parts highly depend on the process parameters employed during fabrication. Thus, depending on the desired properties, the process parameters for a given material need to be optimized for improving the overall reliability of the SLM devices. In this study, design of experiment (DOE) was used to evaluate the dimensional accuracy, composition, and hardness corresponding to the interaction between the SLM process parameters such as laser power (P), scan speed (v), and hatch spacing (h). Contour plots were generated by co-relating the determined values for each characteristic and the process parameters to improve the as-built characteristics of the fabricated IN718 parts and reduce the post-processing time. The outcome of this study shows a range of energy density values for the IN718 superalloy needed to attain optimal values for each of the analyzed characteristics. Finally, an optimal processing region for SLM IN718 fabrication was identified which is in accordance with the values for each characteristic mentioned in literature.
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Zhang, Zhixiong, Chunbing Wu, Tang Li, Keshan Liang, and Yujun Cao. "Design of internal branch support structures for selective laser melting." Rapid Prototyping Journal 24, no. 4 (May 14, 2018): 764–73. http://dx.doi.org/10.1108/rpj-11-2016-0186.
Full textAbstract:
Purpose Selective laser melting (SLM) enables the fabrication of lightweight and complex metallic structures. Support structures are required in the SLM process to successfully produce parts. Supports are typically lattice structures, which cost much time and material to manufacture. Besides, the manufacturability of these supports is undesirable, which may impact the quality of parts or even fail the process. The purpose of this paper is to investigate the efficiency and mechanical properties of advanced internal branch support structures for SLM. Design/methodology/approach The theoretic weight of a branch support and a lattice support of the same plane were calculated and compared. A group of standard candidates of branch support structures were manufactured by SLM. The weight and scanning time of specimens with different design parameters were compared. Then, these samples were tested using an MTS Insight 30 compression testing machine to study the influence of different support parameters on mechanical strength of the support structures. Findings The results show that branch type supports can save material, energy and time used needed for their construction. The yield strength of the branch increases with the branch diameter and inclined branch angle in general. Furthermore, branch supports have a higher strength than traditional lattice supports. Originality/value To the best of the authors’ knowledge, this is the first work investigating production efficiency and mechanical properties of branch support structures for SLM. The findings in this work are valuable for development of advanced optimal designs of efficient support structures for SLM process.