Numerical Simulation of Balling Phenomenon in Metallic Laser Melting Process

2016 ◽  
Author(s):  
Xin Liu ◽  
Mhamed Boutaous ◽  
Shihe Xin ◽  
Dennis Siginer
Keyword(s):  
Numerical Simulation ◽  
Selective Laser Sintering ◽  
Contact Process ◽  
Melting Process ◽  
Complex Model ◽  
Laser Melting ◽  
Powder Bed ◽  
Experimental Works ◽  
3D Numerical Model ◽  
Manufacturing Technologies

As well known, the selective laser Sintering (SLS) is one of the most modern and innovative additive manufacturing technologies with general advantages and wide applications, as a non-contact process, which is flexible, and easily controlled. The choice of process parameters is quite important for laser melting in metallic powder bed. When these parameters are not correctly chosen, particles are either not sintering at all or joining into rather large droplets. This process is named as balling phenomenon, which is extremely unfavorable. In this paper, a 3D numerical model based on discrete element method is proposed in order to study the effect of parameters on the generation of balling droplets in laser melting process. A complex model is developed which couples all phenomena of full SLS process and results of simulations are compared with experimental works of other researchers taken from the literature.

Fundamental Study on Laser Interactions With Nanoparticles-Reinforced Metals—Part II: Effect of Nanoparticles on Surface Tension, Viscosity, and Laser Melting

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Chao Ma ◽  
Jingzhou Zhao ◽  
Chezheng Cao ◽  
Ting-Chiang Lin ◽  
Xiaochun Li
Keyword(s):  
Surface Tension ◽  
Surface Roughness ◽  
Thermophysical Properties ◽  
Melting Process ◽  
Laser Melting ◽  
Fundamental Study ◽  
Laser Polishing ◽  
Laser Manufacturing ◽  
Manufacturing Technologies ◽  
Laser Interactions

It is of great scientific and technical interests to conduct fundamental studies on the laser interactions with nanoparticles-reinforced metals. This part of the study presents the effects of nanoparticles on surface tension and viscosity, thus the heat transfer and fluid flow, and eventually the laser melting process. In order to determine the surface tension and viscosity of nanoparticles-reinforced metals, an innovative measurement system was developed based on the characteristics of oscillating metal melt drops after laser melting. The surface tensions of Ni/Al2O3 (4.4 vol. %) and Ni/SiC (3.6 vol. %) at ∼1500 °C were 1.39 ± 0.03 N/m and 1.57 ± 0.06 N/m, respectively, slightly lower than that of pure Ni, 1.68 ± 0.04 N/m. The viscosities of these Ni/Al2O3 and Ni/SiC MMNCs at ∼1500 °C were 13.3 ± 0.8 mPa·s and 17.3 ± 3.1 mPa·s, respectively, significantly higher than that of pure Ni, 4.8 ± 0.3 mPa·s. To understand the influences of the nanoparticles-modified thermophysical properties on laser melting, an analytical model was used to theoretically predict the melt pool flows using the newly measured material properties from both Part I and Part II. The theoretical analysis indicated that the thermocapillary flows were tremendously suppressed due to the significantly increased viscosity after the addition of nanoparticles. To test the hypothesis that laser polishing could significantly benefit from this new phenomenon, systematic laser polishing experiments at various laser pulse energies were conducted on Ni/Al2O3 (4.4 vol. %) and pure Ni for comparison. The surface roughness of the Ni/Al2O3 was reduced from 323 nm to 72 nm with optimized laser polishing parameters while that of pure Ni only from 254 nm to 107 nm. The normalized surface roughness reduced by nearly a factor of two with the help of nanoparticles, validating the feasibility to tune thermophysical properties and thus control laser-processing outcomes by nanoparticles. It is expected that the nanoparticle approach can be applied to many laser manufacturing technologies to improve the process capability and broaden the application space.

Fundamentals of radiation heat transfer in AlSi10Mg powder bed during selective laser melting

2019 ◽  
Vol 25 (9) ◽  
pp. 1506-1515 ◽  
Author(s):  
Pei Wei ◽  
Zhengying Wei ◽  
Zhne Chen ◽  
Jun Du ◽  
Yuyang He ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Density ◽  
Negative Impact ◽  
Laser Energy ◽  
Melting Process ◽  
Laser Energy Density ◽  
Granular System ◽  
Laser Melting ◽  
Content Type ◽  
Powder Bed

Purpose This paper aims to study numerically the influence of the applied laser energy density and the porosity of the powder bed on the thermal behavior of the melt and the resultant instability of the liquid track. Design/methodology/approach A three-dimensional model was proposed to predict local powder melting process. The model accounts for heat transfer, melting, solidification and evaporation in granular system at particle scale. The proposed model has been proved to be a good approach for the simulation of the laser melting process. Findings The results shows that the applied laser energy density has a significantly influence on the shape of the molten pool and the local thermal properties. The relative low or high input laser energy density has the main negative impact on the stability of the scan track. Decreasing the porosity of the powder bed lowers the heat dissipation in the downward direction, resulting in a shallower melt pool, whereas pushing results in improvement in liquid track quality. Originality/value The randomly packed powder bed is calculated using discrete element method. The powder particle information including particle size distribution and packing density is taken into account in placement of individual particles. The effect of volumetric shrinkage and evaporation is considered in numerical model.

scholarly journals An Overview of Additive Manufacturing Technologies—A Review to Technical Synthesis in Numerical Study of Selective Laser Melting

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3895 ◽  
Author(s):  
Abbas Razavykia ◽  
Eugenio Brusa ◽  
Cristiana Delprete ◽  
Reza Yavari
Keyword(s):  
Numerical Simulation ◽  
Additive Manufacturing ◽  
Selective Laser Melting ◽  
Powder Bed Fusion ◽  
Laser Melting ◽  
Powder Bed ◽  
Part Quality ◽  
Melt Pool ◽  
Wide Range ◽  
Am Processes

Additive Manufacturing (AM) processes enable their deployment in broad applications from aerospace to art, design, and architecture. Part quality and performance are the main concerns during AM processes execution that the achievement of adequate characteristics can be guaranteed, considering a wide range of influencing factors, such as process parameters, material, environment, measurement, and operators training. Investigating the effects of not only the influential AM processes variables but also their interactions and coupled impacts are essential to process optimization which requires huge efforts to be made. Therefore, numerical simulation can be an effective tool that facilities the evaluation of the AM processes principles. Selective Laser Melting (SLM) is a widespread Powder Bed Fusion (PBF) AM process that due to its superior advantages, such as capability to print complex and highly customized components, which leads to an increasing attention paid by industries and academia. Temperature distribution and melt pool dynamics have paramount importance to be well simulated and correlated by part quality in terms of surface finish, induced residual stress and microstructure evolution during SLM. Summarizing numerical simulations of SLM in this survey is pointed out as one important research perspective as well as exploring the contribution of adopted approaches and practices. This review survey has been organized to give an overview of AM processes such as extrusion, photopolymerization, material jetting, laminated object manufacturing, and powder bed fusion. And in particular is targeted to discuss the conducted numerical simulation of SLM to illustrate a uniform picture of existing nonproprietary approaches to predict the heat transfer, melt pool behavior, microstructure and residual stresses analysis.

Finite Element Thermal Analysis of Melt Pool in Selective Laser Melting Process

2018 ◽  
Author(s):  
Zhibo Luo ◽  
Yaoyao Fiona Zhao
Keyword(s):  
Heat Source ◽  
Selective Laser Melting ◽  
Computational Cost ◽  
Melting Process ◽  
Point Heat Source ◽  
Laser Melting ◽  
Line Heat Source ◽  
Powder Bed ◽  
Melt Pool ◽  
Gaussian Point

Selective laser melting is one of the powder bed fusion processes which fabricates a part through layer-wised method. Due to the ability to build a customized and complex part, selective laser melting process has been broadly studied in academic and applied in industry. However, rapidly changed thermal cycles and extremely high-temperature gradients among the melt pool induce a periodically changed thermal stress in solidified layers and finally result in a distorted part. Therefore, the temperature distribution in the melt pool and the size and shape of the melt pool directly determine the mechanical and geometrical property of final part. As experimental trial-and-error method takes a huge amount of cost, different numerical methods have been adopted to estimate the transient temperature and thermal stress distribution in the melt pool and powder bed. The most existing research utilizes the moving Gaussian point heat source to model the profile of the melt pool, which consumes a significant amount of computational cost and cannot be used to implement the part-level simulation. This research proposes a new line heat source to replace the moving point heat source. Some efforts are applied to reduce the computational cost. Specifically, a relatively large step size is used for the line heat source to reduce the number of time steps. In addition, a mesh refinement scheme is adopted to reduce the number of cells in each time step by refining the mesh close to the heat source and coarsening the mesh far away from it. On the other hand, efforts are implemented to increase the accuracy of the simulation result. Temperature-dependent material properties are considered in this FE framework. In addition, material transition among powder, liquid, and solid are incorporated in the developed FE framework. In this study, temperature simulation of one scanning track based on self-developed FE code is applied for Stainless Steel 316L. The simulation results show that the temperature distribution and history of melt pool within line heat source are comparable to that of the moving Gaussian point heat source. While the simulation time is reduced by more than two times depending on the length of line heat input. Therefore, this FE model can be used to numerically investigate the process parameters and help to control the quality of the final part.

Development of productivity estimation model for mass-customized production by selective laser melting

2018 ◽  
Vol 24 (3) ◽  
pp. 670-676 ◽  
Author(s):  
Urska Kostevsek ◽  
Tomaz Brajlih ◽  
Joze Balic ◽  
Žiga Kadivnik ◽  
Igor Drstvensek
Keyword(s):  
Selective Laser Melting ◽  
Selective Laser Sintering ◽  
Real Life ◽  
Individual Case ◽  
Production Method ◽  
Estimation Model ◽  
Laser Melting ◽  
Content Type ◽  
Manufacturing Technologies ◽  
Dental Applications

Purpose Fixed structures in prosthetic dentistry are highly customized products, manufactured individually for patients who have missing teeth. When choosing the technology for fixed dental structure manufacturing, three viable options are available (precise casting, milling and selective laser melting [SLM]). All these technologies can be used to produce a dental structure from CoCr alloy. Besides materials and availability of technologies, economic efficiency is an important factor when choosing a production method. The purpose of this study is to develop an estimation model for achievable productivity of selective laser melting and compare the results with the productivity of conventional manufacturing. Design/methodology/approach Results presented in this paper are based on manufacturing time analysis of an individual case with each of the technologies mentioned above. Because of the efficiency of SLM is highly dependent on how efficiently the work space of the machine is used, this issue was also included in the research. Data used for research were acquired from practical use of each technology in dental applications. Findings Analysis of achievable SLM manufacturing speeds is based on the previous research into manufacturing speeds of additive manufacturing technologies. The presented results present a model that can be used to estimate the productivity of the SLM technology. Research limitations/implications Research was limited to a specific SLM machine type with a fixed workspace volume. Nevertheless, the results show that any SLM machine has to be used as efficiently as possible to be able to be competitive regarding the conventional manufacturing technologies. Practical implications The presented results show clearly at least a rough estimation of what kind of parts and in what volume will be manufactured with an SLM machine prior to buying one. Social implications Results can help to widen the economically efficient way of running SLM machines, replacing conventional manufacturing for medical applications especially with complicated cases. Originality/value A method is presented to adapt the estimation model to a particular real-life production scenario. This method can be used to establish how efficiently selective laser sintering can be used and if using SLM machine instead of conventional manufacturing would be economically viable.

An Object-Oriented Class Library for Scanning Path Generation in SLS/SLM Process

2010 ◽  
Vol 44-47 ◽  
pp. 3309-3313
Author(s):  
Jie Liu ◽  
Yong Qiang Yang ◽  
Jian Bin Lu ◽  
Xu Bin Su
Keyword(s):  
Parallel Computing ◽  
Selective Laser Melting ◽  
Generation Time ◽  
Selective Laser Sintering ◽  
Object Oriented ◽  
Melting Process ◽  
Path Generation ◽  
Laser Melting ◽  
Class Library ◽  
Scanning Path

This paper presents an Object-Oriented class library for scanning path generation in SLS/SLM (Selective Laser Sintering/Selective Laser Melting) process. The classes in the library meet the minimal requirement for the scanning path generation. Specially, in order to take advantage of the Multiprocessor technology and save the generation time, parallel computing is considered in the class library. At last, an application was developed using the class library and an experiment is provided to verify the feasibility of the parallel computing algorithm in the library.

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