Coaxial Monitoring of AISI 316L Thin Walls Fabricated by Direct Metal Laser Deposition

Errico, Vito; Campanelli, Sabina Luisa; Angelastro, Andrea; Dassisti, Michele; Mazzarisi, Marco; Bonserio, C.

doi:10.3390/ma14030673

Cited by 26 publications

(6 citation statements)

References 31 publications

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“…The described attributes distinguish the method presented in this work from other coaxial monitoring systems of laser welding processes. It has been described that coaxial camera monitoring can be used to assess melt pool expansion within the process [23]. However, a topography of the final weld bead cannot be extracted using this method, which means that defects such as pores or similar phenomena can remain hidden from the measurements, which makes the coaxial integration of a camera for melt pool control another indirect process monitoring solution.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Inline Optical Coherence Tomography for Multidirectional Process Monitoring in a Coaxial LMD-w Process

et al. 2022

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Within additive manufacturing, process stability is still an unsolved challenge. Process instabilities result from the complexity of laser deposition processes and the dependence of the quality of the workpiece on a variety of factors in the process. Because a stable process is dependent on many different factors, permanent precise inline monitoring is required. The suitability of the optical coherence tomography (OCT) measuring system integrated into a wire-based laser metal deposition (LMD-w) process for the task of process control results from its high resolution and high measuring speed, and from coaxial integration into the laser process, which allows for a spatially and temporally resolved representation of the weld bead topography during the process. To realize this, a spectral domain OCT (SD-OCT) system was developed and integrated into the beam path of the process laser. With the aid of suitable optics, circular scanning was realized, which allows for the 3D depth information to be displayed independently of the direction of movement of the processing head and the centrally running wire. OCT makes it possible to detect the process-typical topography deviations caused by process variations and thus paves the way for adaptive process control that could make additive laser processes more reproducible and precise in the future.

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Section: Conclusion and Discussionmentioning

confidence: 99%

Inline Optical Coherence Tomography for Multidirectional Process Monitoring in a Coaxial LMD-w Process

et al. 2022

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“…As the laser beam moves, the molten material cools rapidly due to the heat transfer towards the substrate. The solidification front rapidly advances leaving a semi-circular section track of solidified material [15,16]. The quality of the final parts produced by DLMD, in terms of dimensional accuracy and surface regularity, is strongly affected by many process parameters.…”

Section: Introductionmentioning

confidence: 99%

“…Fig 16. Comparison between calculated (solid line) and measured (dotted line) values of the clad width…”

mentioning

confidence: 96%

Influence of standoff distance and laser defocusing distance on direct laser metal deposition of a nickel-based superalloy

Mazzarisi

Errico

Angelastro

et al. 2022

Int J Adv Manuf Technol

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The direct laser metal deposition (DLMD) is an additive manufacturing technology, based on laser cladding, which focuses mainly on 3D manufacturing applications. DLMD allows the production of thin-walled components by overlaying single-track depositions. Several issues can affect the deposition process and compromise the flatness of the surface on which subsequent tracks will be deposited. This work focused on deposition troubles simulated by means of a designed variation of the standoff distance and the laser defocusing distance. The effects of these two important process parameters on the deposition process were investigated. The experimental tests were performed by depositing a nickel-based superalloy powder on AISI 304 stainless steel plates through a coaxial nozzle. The work was carried out using an ytterbium fiber laser source and a deposition head equipped with an advanced and innovative motorized optics system. This allows the decoupled variation of the laser defocusing distance and consequently the laser spot size on the substrate surface with respect to the standoff distance. Results showed an influence of standoff distance and laser defocusing distance on the geometrical characteristics of the clad, such as clad width, clad height, penetration depth, and dilution. An experimental setup consisting of a light coaxial to the powder flow and a laterally positioned camera was designed to investigate the spatial powder distribution. Moreover, an analytical model for the powder distribution and clad width were proposed and validated. The analysis of variance (ANOVA) with a general linear model was also employed to describe the results.

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“…Sörn Ocylok et al [24] monitored the effect of main process parameters (laser power, feed rate, powder mass flow) with camera based co axial monitoring system and reported laser power to be the most influential characteristic in defining melt pool size. Vito Errico et al [25] monitored the melt pool geometry via coaxial monitoring system and used image algorithm to depict the melt pool geometry for fabrication of thin walls using different scan strategies. The literature describes the feasibility of using various monitoring systems for fabrication of thin walls via DED.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Thin Walls with and without Close Loop Control as a Function of Scan Strategy Via Direct Energy Deposition

Ali

Tomesani

Ascari

et al. 2022

Lasers Manuf. Mater. Process.

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Direct Energy Deposition (DED) is a technique used to fabricate metallic parts and is a subcategory of metal additive manufacturing. Despite of its vast advantages over traditional manufacturing the deployment at industrial level is still limited due to underlaying concerns of process stability and repeatability. In-situ monitoring, therefore, is indispensable while depositing via DED. The present experiment is a step towards enhancing our current understanding of the DED when coupled with a closed loop control system to control melt pool width for deposition of thin-walled structures, and as a function of scan strategy. 316L stainless steel powder was deposited on S235JR substrate. A total of 6 iterations are reported, out of many performed, of which 3 were without the closed loop control. Also, to understand the effect of scan strategy as a function of laser power. Two different scan strategies were employed for understanding of the issue i.e., unidirectional, and bidirectional. Apart from the geometrical consistency of the wall, microhardness, density calculations and microstructure were investigated. The geometric consistency was found to be almost perfect with the bidirectional scan strategy. In case of unidirectional scan strategy, the wall shows a negative slope along the other extreme regardless of the closed loop control system. Dilution zone shows the hardness greater than both the substrate and the wall. The specimens fabricated without the use of closed loop control were found to be denser than their counterparts. This was found to be true also in case of manual reduction of power during each layer.

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Coaxial Monitoring of AISI 316L Thin Walls Fabricated by Direct Metal Laser Deposition

Cited by 26 publications

References 31 publications

Inline Optical Coherence Tomography for Multidirectional Process Monitoring in a Coaxial LMD-w Process

Inline Optical Coherence Tomography for Multidirectional Process Monitoring in a Coaxial LMD-w Process

Influence of standoff distance and laser defocusing distance on direct laser metal deposition of a nickel-based superalloy

Fabrication of Thin Walls with and without Close Loop Control as a Function of Scan Strategy Via Direct Energy Deposition

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