Capacitive Imaging applied for In-Situ Powder Topographic Characterization during Powder Bed Fusion

Abstract

Capacitive imaging is proposed for topographic characterization of the surface of successive powder layers during powder bed
fusion additive manufacturing. This capability enables new opportunities for early detection and, ultimately, prevention of defective
conditions by using extensive capacitive sensor arrays integrated into the recoater unit. Finite element modeling was used to simulate
individual capacitive sensors in order to identify a suitable geometry for implementation in an array. A 12 sensors array was
designed and demonstrated while integrated with compact readout electronics instrumentation. Surface topographic irregularities
were simulated by confining SS316 powder against a thin glass cylinder, on which various plastic structures were fabricated. The
sensors and associated electronics demonstrated the ability to detect cylindrical and linear voids with radii/widths as small as
0.55 mm and depths of 0.1 mm.