Spatter Simulation And Study Of Wave Stripe Partition Strategy During Laser Powder Bed Fusion

Laser Powder Bed Fusion(LPBF)technology uses laser high energy input to melt the powder material layer by layer.With the characteristics of convenience,customization,high processing accuracy,it is suitable for manufacturing a variety of complex parts rapidly.However,the LPBF technology in processing size of part has limitation and its prototyping efficiency is low.With the increasing industrial demand,LPBF has developed a multi-laser LPBF(M-LPBF)technology to overcome its limitations in large parts,and M-LPBF technology will become a trend in the future.However,with the development of M-LPBF processing technology,there are many factors inevitably,such as spatters,overlapping areas,which affect the quality of molded parts.Therefore,studying the spatter deposition law and scanning strategy play a great role in the processing quality and efficiency of M-LPBF processing.Based on the study that the gas flow influencing on spatter removal in LPBF equipment and spatter simulation at home and abroad,a spatter model is constructed and the spatter deposition distribution is analyzed.Besides,the overlap ways of the junction zone in scanning strategy is studied,which affects surface quality and mechanical properties of parts.The main contents of this research are as follows:(1)With different scanning strategies,how gas flow influences on spatters and carry spatter away in LPBF and where spatters deposit are be studied.A reasonable fluid domain in the printed area for Computational Fluid Dynamics Discrete(CFD)simulation is designed to obtain a good gas flow environment.According to the three kinds of spatters including entrainment spatter,metal/ solid spatter and powder agglomeration spatter generated by the molten pool during the single laser LPBF process,a spatter injection model with a certain initial speed and direction is established in EDEM software with the method of Discrete Element Method(DEM).CFD-EDM gas-solid interaction simulation has done to analyze the spatter particle settlement and its regularity with the influence of gas flow.The better distribution of spatter deposition is obtained by the dual-repeating scanning strategy.Spatters deposit closer to the outlet by the negative to gas flow scanning strategy,which are easier to be removed.(2)The ways of lap in different Partition strategies has influence on the quality of LPBF processing.Based on the simulation results of better spatter removal rate by the negative to gas flow scanning strategy and better distribution of the dual-repeating scanning strategy,it has priority to be considered in the new scanning strategy.Besides,the paper analyzes the way of horizontal lap of stripe scanning strategy and the way of horizontal and vertical lap of the checkerboard scanning strategy,and their advantages and disadvantages.Combining with their advantages,a partition scanning strategy is proposed to optimize the lapping ways to improve the surface molding quality of the junction zone.The Visual Studio C# is used to design and realize the proposed partition scanning strategy.Through reading the slice model data,filling the slice outline with paths,visualizing the path planning,and outputting the print file for the device,parts are processed,then are analyzed.Experimental results show that the scanning strategy can improve the void in the lapping area,improve the surface morphology,and improve the mechanical properties of the parts.