| Selective laser melting is one of the highly promising technologies for additive manufacturing of metals.Because of its advantages of high molding accuracy,wide range of available materials,and the ability to mold complex metal parts,it has been widely used in fields such as aerospace,automotive molds,and biomedical.In the process of selective laser melting,the process by-products such as spatter and soot generated by high energy laser melting metal powder can affect the quality of the formed parts.The atmosphere circulation system in SLM equipment is the main way to remove spatter,soot and other process by-products.The duct structure in the build chamber has an important influence on the flow field distribution and the removal probability of spatter,so it is important to optimize the duct structure in the build chamber.In this paper,based on the EOS M290 selective laser melting equipment,a gas-solid two-phase flow model for the build chamber was established,and the motion paths of spatter particles with different diameters and the removal probability of spatter of different materials were analyzed.Secondly,the influences of inlet velocity,inlet diameter,inlet stretch length,outlet grid number,inlet and outlet height on the flow field distribution and removal probability of spatter in the build chamber were investigated.Finally,based on the response surface method,the removal probability of spatter under the interaction of different influencing factors was analyzed,and the relevant optimal process parameters were obtained.The main research contents are as follows:(1)A gas-solid two-phase flow model was established for the build chamber of EOS M290 selective laser melting equipment.The motion paths of spatter particles with different diameters and the removal probability of spatter of different materials were analyzed.It is found that the motion path of spatter particles with different diameters is different.The diameter of spatter particles increases from 60 μm to 240μm,and the length of the motion path of spatter particles in the horizontal direction decreases from 216.85 mm to 28.86 mm.The density of spatter particles has a great influence on the removal probability of spatter.When the inlet speed is 3 m/s,the removal probability of spatter of SS316 L stainless steel,Ti6Al4 V titanium alloy and Al Si10 Mg aluminum alloy are 69.25%,91.6% and 96.96%,respectively.(2)Based on the numerical simulation technique,the influence law of flow field distribution and the removal probability of spatter in the build chamber under different influencing factors was analyzed.It was found that with the increase of the inlet air velocity,the removal probability of spatter increased linearly.Under the condition that the powder bed was not destroyed(the air velocity at 1 mm above the powder bed was less than 3.383 m/s),the maximum inlet air velocity of the original equipment was 4.28m/s.With the increase of the inlet hole diameter,inlet hole stretching length,outlet grille number and inlet and outlet height,the overall trend of the removal probability of spatter increases first and then decreases.(3)The factor levels were selected based on the results of the single factor analysis study,and the process parameters affecting the removal probability of spatter were further optimized based on the response surface method.The study found that the impact of inlet velocity,inlet diameter,and outlet grid number on the removal probability of spatter is significant.The interaction between inlet velocity and inlet diameter,between inlet velocity and outlet grid number,and between inlet diameter and outlet grid is significant.The optimal process parameters obtained from the response surface method are inlet velocity 4 m/s,inlet diameter 3.91 mm,and outlet grid number 8.The simulation calculation shows that the removal probability of spatter under the optimal process parameters is 85.03%,and the relative error with the predicted value of the response surface model is only 0.83%. |
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