Study on the numerical simulation of laying powder for the selective laser melting process

Because the selective laser melting (SLM) formation process involves rapid melting and solidification of slices, the SLM process places high demands on the tightness, uniformity, and flatness of the powder layer. Based on the discrete element method (particle contact force model, particle collision judgment algorithm, and particle motion equation) and the SLM laying powder process, a numerical simulation of the SLM laying powder process was carried out. For the performance measurement experiment of the TC4 titanium alloy powder, the powder bulk density, tap density, and angle of repose were calculated and analyzed. It was found that the tap density increased by 7.5% compared to the bulk density, and the calculated average angle of repose (32.6 degrees) was in good agreement with the experimental data (33.2 degrees), thus verifying the accuracy of the calculation model used for the SLM laying powder. The influences of different scraping methods and scraping speeds on the quality of the laying powder were calculated and analyzed. It was found that the scraping method using a roller (not rotating) obtained the highest tightness and most uniform powder distribution, and, as the scraping speed increased, the laying tightness tended to decrease linearly. The results of the numerical simulation study of the SLM laying powder process can be used to guide the actual SLM laying powder process and, alternatively, provide basic data for the numerical simulation of SLM molten pool dynamics based on the particle scale.