A novel experimental setup to study powder spreading with a wide range of process conditions

The ease of powder spreading for the Powder Bed Fusion (PBF) process differs from flowability [1,2]. Therefore, spreadability has to be tested using specifically designed setups and procedures. Some experiments revealed poor spreadability performances of purposely designed powders at temperatures in the windows of process applications [3,4] . The source of discrepancy with these results may rely on the method adopted to feed the powder to the system and on the spreader geometry. In this project, a spreading apparatus was built to investigate different powders’ spreadability at different temperatures and powder feeding and spreading conditions. This equipment has interchangeable steel plates bearing square-shaped engravings to simulate the region where the powder bed is built. Two different spreading devices can be used: a blade or a roller. Horizontal motion actuators allow moving the spreading device forward at a speed similar to those in real PBF systems. A different high-precision actuator ensures accurate vertical positioning of the spreading tool to accurately define the gap between the spreading device and the working plate. The heating system is made of radiative elements mounted on the wall of a removable insulated cover and a conduction heating pad below the steel plate. The heated cover and the heating pad have two separate control systems to control the working plate’s temperature and the fed particles separately. The setup will allow spreadability procedures for single- and multi-layer experiments. At the end of the spreading experiment, a high-resolution camera is used to acquire highly resolved images of the powder bed taken with grazing light. Image analysis of the pictures is used to evaluate the homogeneity of the bed. Assuming shadows are related to powder roughness, the procedure allows for evaluating surface homogeneity.