scholarly journals The effects of locations on the build tray on the quality of specimens in powder bed additive manufacturing

2021 ◽  
Author(s):  
Snehashis Pal ◽  
Nenad Gubeljak ◽  
Tonica Bončina ◽  
Radovan Hudák ◽  
Teodor Toth ◽  
...  
Keyword(s):  
Main Role ◽  
Particle Sizes ◽  
Additional Experiment ◽  
Powder Bed ◽  
Melt Pool ◽  
Start Line ◽  
Sample Density ◽  
Powder Layering ◽  
Pool Formation

AbstractIn this study, the effect of powder spreading direction was investigated on selectively laser-melted specimens. The results showed that the metallurgical properties of the specimens varied during fabrication with respect to their position on the build tray. The density, porosity, and tensile properties of the Co–Cr–W–Mo alloy were investigated on cuboid and tensile specimens fabricated at different locations. Two different significant positions on the tray were selected along the powder spreading direction. One set of specimens was located near the start line of powder spreading, and the other set was located near the end of the building tray. The main role in the consequences of powder layering was played by the distribution of powder particle sizes and the packing density of the layers. As a result, laser penetration, melt pool formation, and fusion characteristics varied. To confirm the occurrence of variations in sample density, an additional experiment was performed with a Ti–6Al–4V alloy. Furthermore, the powders were collected at two different fabricating locations and their size distribution for both materials was investigated.

Discrete Element Modeling of Scraping Process and Quantification of Powder Bed Quality for SLM

2020 ◽  
Author(s):  
Kuldeep Mandloi ◽  
Parth Amrapurkar ◽  
Harish P. Cherukuri
Keyword(s):  
Particle Size ◽  
Volume Fraction ◽  
Numerical Models ◽  
Discrete Element ◽  
Contact Model ◽  
Powder Particle Size ◽  
Particle Sizes ◽  
Powder Bed ◽  
Size And Shape

Abstract In selective laser melting (SLM) and selective laser sintering (SLS) additive manufacturing techniques, the powder spreading process plays a key role in the quality of the manufactured parts. Some of the important parameters that influence the quality of the powder bed are the powder particle size distribution, spreader-type (roller or blade), spreader speed, size and shape of the particles. In this work, we use the discrete element method to study the effect of these parameters on the quality of the powder bed. The interactions between the particles is modeled using Hertz-Mindlin contact model as well as Hertz-Mindlin with JKR contact model with the latter being used for studies of the effect of cohesiveness of particles on powder bed quality. The Dynamic Repose Angle (DRA) is used for validating the numerical models. Our studies differ from the previous studies in that we have introduced quantitative measures for powder bed quality in the form of Discretized Volume Fraction (DVF) and Particle Flow Rate (PFR) for the layering process. With the help of these quantities, we studied various factors that affect powder bed quality: cohesiveness of the particles, spreader shape, particle size and shape, and the distribution of particle sizes. Our results indicate that as DVF and PFR decrease and DRA increases, the potential for cavities and shifting defects increases due to increase in cohesiveness. Use of fixed particle size in the simulations leads to higher DRA than when a normal distribution of particle sizes is considered. Our results show that the roller geometry provides better bed quality as compared to the blade type geometry.

scholarly journals Evaluation of spatter particles, metal vapour jets, and depressions considering influence of laser incident angle on melt pool behaviour

2021 ◽  
Author(s):  
Kotaro Tsubouchi ◽  
Tatsuaki Furumoto ◽  
Mitsugu Yamaguchi ◽  
Atsushi Ezura ◽  
Shinnosuke Yamada ◽  
...  
Keyword(s):  
Laser Beam ◽  
High Speed ◽  
Incident Angle ◽  
Three Dimensional ◽  
Burial Depth ◽  
Metal Vapour ◽  
Building Conditions ◽  
Powder Bed ◽  
Melt Pool ◽  
Pool Formation

Abstract Building of practical parts involves the application of metal-based laser powder bed fusion using a laser beam (PBF-LB/M) owing to its high-precision manufacturing. However, the quality of the built parts obtained via the PBF-LB/M processes varies with the building conditions, and a thorough understanding of the building mechanism has not been achieved owing to the complex and interrelated process parameters involved. The incident angle of the laser beam, which changes on the platform during the laser beam scan owing to the designed three-dimensional data, is among the principal parameters that affects the building aspects. In this study, the melt pool in the singletrack formation during the PBF-LB/M processes was visualised using a high-speed camera, and the influence of the laser incident angle on the ejection characteristics of spatter particles formed around the laser-irradiated area was investigated. Consequently, the spatter particles and metal vapour jet behaviour varied with the laser incident angle. There was a reduction in number of spatter particles owing to the origin of the incident direction being from behind the laser irradiation area. In addition, the laser incident angle also affected the melt pool morphology because of the depression in the melting. Furthermore, the burial depth of the pores varied with the laser incident angle, and is related to the depth of the depression during the melt pool formation.

scholarly journals Formation processes for large ejecta and interactions with melt pool formation in powder bed fusion additive manufacturing

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Abdalla R. Nassar ◽  
Molly A. Gundermann ◽  
Edward W. Reutzel ◽  
Paul Guerrier ◽  
Michael H. Krane ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Formation Processes ◽  
Powder Bed Fusion ◽  
Powder Bed ◽  
Melt Pool ◽  
Pool Formation

scholarly journals Finite Element Modeling of Melt Pool Dynamics in Laser Powder Bed Fusion of 316L Stainless Steel

2021 ◽  
Author(s):  
Juan Trejos-Taborda ◽  
Luis Reyes-Osorio ◽  
Carlos Garza ◽  
Patricia del Carmen Zambrano-Robledo ◽  
Omar Eduardo Lopez-Botello
Keyword(s):  
Numerical Model ◽  
Relative Error ◽  
Laser Scanning ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Melt Pool ◽  
History Of ◽  
Dynamics Stability

Abstract In Laser Powder Bed Fusion (LPBF), melt pool dynamics stability determines the overall quality of a manufactured component. In this work, a numerical model of the LPBF process was developed in order to study and fully understand the behavior of the melt pool dynamics. The numerical model takes into account most of the manufacturing parameters, thermophysical properties, an enhanced thermal conductivity approach and a volumetric heat source in order to precisely mimic LPBF. This research assumes that the energy emitted by the laser interacts with the metal powder with an absorptivity gradient through the layer thickness in order to calculate the thermal history of the process and the evolution of the melt pool dimensions. The obtained results determined that melt pool dimensions follow a thermal pattern, which is caused by the laser scanning strategy of the LPBF process. A new effective width criterion was proposed in the present research in order to accurately relate both calculated and measured dimensions of the melt pool, reducing the relative error of the model and obtaining data scattering with a standard deviation of ±7.21 µm and a relative error of 2.92%.

scholarly journals Process characterization and analysis of ceramic powder bed fusion

2021 ◽  
Author(s):  
Kevin Florio ◽  
Dario Puccio ◽  
Giorgio Viganò ◽  
Stefan Pfeiffer ◽  
Fabrizio Verga ◽  
...  
Keyword(s):  
High Speed ◽  
Ceramic Powder ◽  
Integrating Sphere ◽  
Alumina Powder ◽  
Powder Bed Fusion ◽  
Single Track ◽  
Ceramic Powders ◽  
Pure Alumina ◽  
Powder Bed ◽  
Melt Pool

AbstractPowder bed fusion (PBF) of ceramics is often limited because of the low absorptance of ceramic powders and lack of process understanding. These challenges have been addressed through a co-development of customized ceramic powders and laser process capabilities. The starting powder is made of a mix of pure alumina powder and alumina granules, to which a metal oxide dopant is added to increase absorptance. The performance of different granules and process parameters depends on a large number of influencing factors. In this study, two methods for characterizing and analyzing the PBF process are presented and used to assess which dopant is the most suitable for the process. The first method allows one to analyze the absorptance of the laser during the melting of a single track using an integrating sphere. The second one relies on in-situ video imaging using a high-speed camera and an external laser illumination. The absorption behavior of the laser power during the melting of both single tracks and full layers is proven to be a non-linear and extremely dynamic process. While for a single track, the manganese oxide doped powder delivers higher and more stable absorptance. When a full layer is analyzed, iron oxide-doped powder is leading to higher absorptance and a larger melt pool. Both dopants allow the generation of a stable melt-pool, which would be impossible with granules made of pure alumina. In addition, the present study sheds light on several phenomena related to powder and melt-pool dynamics, such as the change of melt-pool shape and dimension over time and powder denudation effects.

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