Laboratory simulation of capacitance-based layer-by-layer monitoring of three-dimensional printing

This paper provides a novel method of three-dimensional (3D) printing monitoring. The method is applicable to monitoring the printing of metals and polymers. The effectiveness of the method is shown by laboratory simulation. The method involves two coplanar electrodes that are electrically conductive and positioned on a substrate (build plate), which is substantially electrically non-conductive. The proximate edges of the electrodes are essentially parallel and are separate from one another. The area of the electrodes is substantially smaller than the area of the substrate. An AC current flows between the two electrodes, such that it partly flows in each of the layers in the build. In the monitoring, the capacitance between the two electrodes is measured using an LCR meter at 2.000 kHz. The AC voltage is 1.000 V. In case of metal printing, the demonstration involves aluminum layers (16 μm thick) on an alumina substrate and the two electrodes are preferably electrically connected. The layer-by-layer monitoring is effective for electrode spacing up to 76 mm. The electric field between the two electrodes spreads to the regions beyond the region between the two electrodes, thus enabling the monitoring of printed layers in the region between the electrodes as well as the regions in the vicinity of the electrodes. The technique is effective for following the progress of layer-by-layer printing and for detecting defects in a printed layer.