Novel testing device and routine to characterise the spreadability of powders for powder bed fusion processes – a problem-oriented approach

ABSTRACT Currently there is considerable interest in understanding and quantifying the powder characteristics that affect the quality of the top spread powder layer for processes such as powder bed fusion and binder jetting. For this purpose, a new testing device has been developed in order to assess several aspects of this top spread powder layer. Using different measurement procedures, the roughness of the top layer, the surface coverage of a single spread powder layer and the powder bed density of an entire spreading experiment can be determined. Since the tester is freely programmable, the individual process steps of spreading a single powder layer can also be varied. Using these methods, the influence of different process parameters such as e.g. the spreading velocity or the distance between the blade and the building platform, which is also referred to as gap size in general, on the quality of the top or only a single spread layer and on the powder bed packing density can be examined. This study presents the new test device as well as the corresponding measurement procedures mentioned, the reproducibility of the results, which, depending on the measurement method and the measured parameter, range between 0.24 and 4.81%, and the influence of the spreading strategy, which defines the chronological order of the single steps during spreading.