Discrete Element Simulations of Powder Spreading in Additive Manufacturing

Powder spreading plays a critical role in the quality of parts produced with selective laser sintering (SLS). Some of the important parameters that influence the quality of the powder bed are the powder particle size and distribution, blade speed, blade - bed gap. In this work, the discrete element method is used to study the effect of these parameters on the quality of the powder bed. The interaction between the particles is modelled using Hertz-Mindlin with JKR contact model. The powder bed quality is quantified in the terms of mass flow rate (MFR) and packing density (PD) of powder. It is widely reported in the literature that increasing the packing density has the effect of reducing defects in the finished product. With the help of these quantities various factors affecting the powdered bed quality have been studied: cohesiveness of the particles, coefficient of restitution (COR), powder particle size and distribution, blade speed and gap. The results obtained from this study indicate that the powder particle size distribution is one of the major factor affecting the bed quality and as the blade - bed gap increases and blade speed decreases packing density increases. The blade - bed gap has no impact on MFR of the powder and cohesiveness has a wider impact on PD with smaller particle diameter.