On the measurement of effective powder layer thickness in laser powder-bed fusion additive manufacturing of metals

2018 ◽  
Vol 4 (2) ◽  
pp. 109-116 ◽  
Author(s):  
Yahya Mahmoodkhani ◽  
Usman Ali ◽  
Shahriar Imani Shahabad ◽  
Adhitan Rani Kasinathan ◽  
Reza Esmaeilizadeh ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Layer Thickness ◽  
Powder Layer ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed

Camera signal dependencies within coaxial melt pool monitoring in laser powder bed fusion

2020 ◽  
Vol 26 (1) ◽  
pp. 100-106 ◽  
Author(s):  
Tobias Kolb ◽  
Reza Elahi ◽  
Jan Seeger ◽  
Mathews Soris ◽  
Christian Scheitler ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Layer Thickness ◽  
Powder Layer ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Content Type ◽  
Powder Bed ◽  
Sensory Signals ◽  
Melt Pool ◽  
Research Activities

Purpose The purpose of this paper is to analyse the signal dependency of the camera-based coaxial monitoring system QMMeltpool 3D (Concept Laser GmbH, Lichtenfels, Germany) for laser powder bed fusion (LPBF) under the variation of process parameters, position, direction and layer thickness to determine the capability of the system. Because such and similar monitoring systems are designed and presented for quality assurance in series production, it is important to present the dominant signal influences and limitations. Design/methodology/approach Hardware of the commercially available coaxial monitoring QMMeltpool 3D is used to investigate the thermal emission of the interaction zone during LPBF. The raw images of the camera are analysed by means of image processing to bypass the software of QMMeltpool 3D and to gain a high level of signal understanding. Laser power, scan speed, laser spot diameter and powder layer thickness were varied for single-melt tracks to determine the influence of a parameter variation on the measured sensory signals. The effects of the scan direction and position were also analysed in detail. The influence of surface roughness on the detected sensory signals was simulated by a machined substrate plate. Findings Parameter variations are confirmed to be detectable. Because of strong directional and positional dependencies of the melt-pool monitoring signal a calibration algorithm is necessary. A decreasing signal is detected for increasing layer thickness. Surface roughness is identified as a dominating factor with major influence on the melt-pool monitoring signal exceeding other process flaws. Research limitations/implications This work was performed with the hardware of a commercially available QMMeltpool 3D system of an LPBF machine M2 of the company Concept Laser GmbH. The results are relevant for all melt-pool monitoring research activities connected to LPBF, as well as for end users and serial production. Originality/value Surface roughness has not yet been revealed as being one of the most important origins for signal deviations in coaxial melt-pool monitoring. To the best of the authors’ knowledge, the direct comparison of influences because of parameters and environment has not been published to this extent. The detection, evaluation and remelting of surface roughness constitute a plausible workflow for closed-loop control in LPBF.

scholarly journals Increasing the Productivity of Laser Powder Bed Fusion for Stainless Steel 316L through Increased Layer Thickness

2020 ◽  
Author(s):  
Alexander Leicht ◽  
Marie Fischer ◽  
Uta Klement ◽  
Lars Nyborg ◽  
Eduard Hryha
Keyword(s):  
Stainless Steel ◽  
Layer Thickness ◽  
Electron Backscatter Diffraction ◽  
Powder Layer ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Stainless Steel 316L ◽  
Powder Bed ◽  
Backscatter Diffraction ◽  
Am Processes

AbstractAdditive manufacturing (AM) is able to generate parts of a quality comparable to those produced through conventional manufacturing, but most of the AM processes are associated with low build speeds, which reduce the overall productivity. This paper evaluates how increasing the powder layer thickness from 20 µm to 80 µm affects the build speed, microstructure and mechanical properties of stainless steel 316L parts that are produced using laser powder bed fusion. A detailed microstructure characterization was performed using scanning electron microscopy, electron backscatter diffraction, and x-ray powder diffraction in conjunction with tensile testing. The results suggest that parts can be fabricated four times faster with tensile strengths comparable to those obtained using standard process parameters. In either case, nominal relative density of > 99.9% is obtained but with the 80 µm layer thickness presenting some lack of fusion defects, which resulted in a reduced elongation to fracture. Still, acceptable yield strength and ultimate tensile strength values of 464 MPa and 605 MPa were obtained, and the average elongation to fracture was 44%, indicating that desirable properties can be achieved.

scholarly journals Simulation Study of Hatch Spacing and Layer Thickness Effects on Microstructure in Laser Powder Bed Fusion Additive Manufacturing using a Texture-Aware Solidification Potts Model

2021 ◽  
Author(s):  
Joseph Pauza ◽  
Anthony Rollett
Keyword(s):  
Additive Manufacturing ◽  
Layer Thickness ◽  
Potts Model ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Microstructure Control ◽  
Powder Bed ◽  
Laser Parameters ◽  
Link Type ◽  
Hatch Spacing

AbstractMicrostructure control in the laser powder bed fusion additive manufacturing processes is a topic of major interest because of the submillimeter length scale at which the manufacturing process occurs. The ability to control the process at the melt pool scale allows for microstructure control that few other manufacturing techniques can match. The majority of work on microstructure control has focused on altering laser parameters to control solidification conditions (Ref (R.R. Dehoff, M.M. Kirka, W.J. Sames, H. Bilheux, A.S. Tremsin, L.E. Lowe, and S.S. Babu, Site Specific Control of Crystallographic Grain Orientation through Electron Beam Additive Manufacturing, Mater. Sci. Technol., 2014, 31(8), p 931–938. R. Shi, S.A. Khairallah, T.T. Roehling, T.W. Heo, J.T. McKeown, and M.J. Matthews, Microstructural Control in Metal Laser Powder Bed Fusion Additive Manufacturing Using Laser Beam Shaping Strategy, Acta Mater., 2020, 184, p 284–305, https://doi.org/10.1016/j.actamat.2019.11.053.)). Other machine parameters, besides the laser parameters, have also been shown to affect the microstructure of AM parts (Ref (N. Nadammal, S. Cabeza, T. Mishurova, T. Thiede, A. Kromm, C. Seyfert, L. Farahbod, C. Haberland, J.A. Schneider, P.D. Portella, and G. Bruno, Effect of Hatch Length on the Development of Microstructure, Texture and Residual Stresses in Selective Laser Melted Superalloy Inconel 718, Mater. Des., 2017, 134, p 139–150, https://doi.org/10.1016/j.matdes.2017.08.049. F. Geiger, K. Kunze, and T. Etter, Tailoring the Texture of IN738LC Processed by Selective Laser Melting (SLM) by Specific Scanning Strategies, Mater. Sci. Eng. A, 2016, 661, p 240–246, https://doi.org/10.1016/j.msea.2016.03.036.)). We propose an investigation of the effects of hatch spacing and layer thickness on microstructure development in laser powder bed fusion additive manufacturing. A Monte Carlo Potts model with textured solidification capabilities is used to study the effects of these parameters on a unidirectional scan strategy. The simulation results reveal substantial changes in grain morphology as well as texture. Additionally, EVP-FFT crystal plasticity simulations were performed to evaluate the effect of the microstructural shifts on mechanical response. The conclusions from this work elucidate the effects of these parameters on part microstructure as predicted by the texture-aware solidification Potts model and inform understanding of how bulk texture is predicted by the simulation approach.

Effect of higher layer thickness on laser powder bed fusion built single tracks of Ni-Cr-Fe-Nb-Mo alloy

2021 ◽  
pp. 251659842110368
Author(s):  
S. K. Nayak ◽  
S. K. Mishra ◽  
C. P. Paul ◽  
K. S. Bindra
Keyword(s):  
Aspect Ratio ◽  
Layer Thickness ◽  
Process Parameters ◽  
Powder Layer ◽  
Beam Diameter ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Track Width ◽  
Powder Bed ◽  
Building Engineering

Laser Powder Bed Fusion (LPBF) is one of the revolutionary technologies that can fabricate complex-shaped components by selective melting of the pre-placed powder layer, using high-power laser as directed by the input digital files. Generally, research on the LPBF process is called out for layer thickness (LT) up to 50 µm and smaller beam diameter (≤100 µm), but it has lower productivity. In LPBF, higher productivity can be achieved with higher LT (>50 µm), but it consists of various process instabilities. In the present work, parametric studies are performed by laying Ni-Cr-Fe-Nb-Mo single tracks, using LPBF at higher LT. The process parameters such as laser power ( P), scan speed ( v), and LT are varied among 150–450 W, 0.04–0.1 m s−1, and 80–160 µm, respectively, at three levels each. For the range of parameters under investigation, the maximum track width of 610 µm and aspect ratio of 7.63 are achieved at a P of 450 W and v of 0.04 m s−1 at 80 µm LT. It is observed that an increase in the energy density and layer thickness resulted in the reduction of track width and aspect ratio due to material vaporization occurring from poor heat conductivity due to unconventionally high powder layer thickness. It is also observed that the build rate increases with an increase in P, v, and LT. As single tracks are basic building blocks, the obtained results can provide an insight into the effect of process parameters on LPBF-built single tracks at higher LT for building engineering components of required width with higher build rate. Furthermore, the track dilution is also found to increase with the increase in P and decrease in v.

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