The quality of parts manufactured by laser powder bed fusion is closely related to the uniformity and density of the powder bed. In this work, the discrete element method is used to simulate the powder spreading process by different spreader geometries with rough substrate surfaces. The results indicate that reducing the spreader inclination angle significantly increases the number of force chains, enhances compaction, and consequently improves the quality of the powder bed. Studies also show that optimizing the bottom structure of the spreader can effectively reduce exposed areas. An arc-shaped structure promotes particle packing and filling, improving the powder distribution characteristics. A narrow spreader significantly affects the packing density of the powder bed at low layer gaps, whereas a wide spreader is relatively less constrained. At high spreading speeds, the spreader with an inclination angle of 135° produces the highest quality of the powder bed. R1000 performs excellently at larger layer gaps. The above findings provide valuable guidance for optimizing powder spreading strategies in the laser powder bed fusion process. ... Read more

Controlling the quality of the powder bed is critical for guaranteeing component quality in laser powder bed fusion (LPBF). In this work, the discrete element method is used to examine how substrate surface morphology, including the roughness and texture angle, affects powder bed quality. The results indicate that the bed quality is more sensitive to changes in surface roughness than texture angle. Powder coverage can be improved by increasing the texture angle. The force analysis reveals that on rough surfaces, the contact force acting on the substrate has strong fluctuations. The particle-substrate contact force under the piles has an increasing-decreasing trend with the distance from the scraper increasing. In addition, the in-situ re-coating technique at a proper gap increment can effectively fill the depressions generated from the rough surface, achieving more uniform and dense powder beds. The findings provide a theoretical basis for optimizing powder-spreading strategies in LPBF process. ... Read more