Forced Convection in a Polymeric Powders

In a Selective Laser Sintering (SLS) powder bed, thermal transfer occurs through multiple modes. Forced convection through the powder, or downdraft, has recently been implemented in SLS machines in an effort to enhance thermal transfer within the powder bed. In this paper, forced convection is analytically shown to be a significant thermal transfer mode for low porosities, such as seen in SLS powder beds. A polymeric powder bed subjected to downdraft is investigated with the goal of quantitatively determining thermal behavior. A numerical model describing heat transfer within a powder is presented. The design and construction of an experimental apparatus to measure the temperature profiles within a powder subjected to forced convection is described. Using the information gained in these experiments, it may be possible to better control the thermal environment of SLS powder beds, reducing growth and internal stress build-up.