The Effect of Powder Flowability in the Selective Laser Sintering Process
The flowability of powder material has a significant effect on powder paving quality during selective laser sintering (SLS) and the mechanical properties of the sintered components. The flowability depends on several factors, such as particle size distrib
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Abstract The flowability of powder material has a significant effect on powder paving quality during selective laser sintering (SLS) and the mechanical properties of the sintered components. The flowability depends on several factors, such as particle size distribution, particle shape, and environmental temperature, etc. In general, the virgin powder possesses good flowability. The used powder which remained in forming cave after sintering cannot be reused for next SLS processing alone. In order to make full use of powder materials, and meet the mechanical properties requirements of the sintered component, it is very important to understand the flowability of the used powder. To produce a component with uniform density and small porosity, the reasonable mass ratio between virgin powder and the used powder (Rv-u) is required. The index of HR, and angle of repose were applied to character the flowability of powders in the study. The particle size distribution and particle shape of both virgin powder and used powder, and their impact on flowability were measured. The discrete element models of virgin powder and used powder were developed and the paving process was simulated. The surface roughness and mechanical properties of sintering components with different Rv-u were investigated. The surface roughness of component sintered by used powder is the worst. There exist less distinctions of the modular of elasticity and the tensile strengths among the three kinds of Rv-u. The numerical results show that the apparent density and density uniformity of the powder bed has little difference by changing the Rv-u, while the results were confirmed by experiments.
Y. Tan (&) Institute of Manufacturing Engineering, Huaqiao University, Xiamen 361021, China e-mail: [email protected] J. Zheng W. Gao S. Jiang School of Mechanical Engineering, Xiangtan University, Xiangtan 411105, China Y. Feng School of Engineering, Civil and Computational Engineering Centre, University of Wales Swansea, Swansea SA2 8PP, UK © Springer Science+Business Media Singapore 2017 X. Li et al. (eds.), Proceedings of the 7th International Conference on Discrete Element Methods, Springer Proceedings in Physics 188, DOI 10.1007/978-981-10-1926-5_65
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1 Introduction Nylon powder materials, with low melting point and lower surface energy, require lower laser power for sintering. They are the most successful raw materials for selective laser sintering (SLS) [1]. In the process of SLS, powder paving has the important influence on the sintered components. The density uniformity and smoothness of powder bed is the assurance for suitable mechanical properties and accuracy of sintered components. Li [2] described the particles velocity in paving process by mathematical method. Based on the analysis results, the main parameters which have effect on the powder paving had been proposed. The influences of these parameters on the powder paving process were investigated combined with the experiment and the mathematics analysis method. A set of opti
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