An Interface-based Geometry-Dependent Layer Height Model for 3D Inkjet Printing

Three-dimensional inkjet printing (3D-IJP) enables high-accuracy fab-rication of microscale features through droplet-based additive manufacturing with minimal material waste. Precise control of layer height is essential for di-mensional accuracy and collision-free printing, as the final part dimensions are the cumulative result of printed layers. Layer height is determined by a complex interplay of ink properties, substrate properties, and printing process parameters. This study investigates the effects of print resolution (360 - 1080 dpi), number of layers (1 - 4 layers), and width of the printed features (1 - 16 pixels) on the aver-age layer height evaluated using confocal microscopy. The surface energy of the printed and cured inkjet material, the substrate, and the contact angle between the ink droplet and substrate or printed layer are evaluated using the sessile drop method. At lower print resolution (360 dpi), the printed droplets remain isolated, whereas at higher print resolution a homogeneous layer is formed at a droplet overlap of 21% (720 dpi). The second layer is considerably flatter than the 1st layer due to differences in surface energy between the substrate and the printed layer, and the leveling effect of an additional layer. ... mehrAt higher print resolution (1080 dpi, 31% overlap), increasing the number of adjacent droplet rows and number of layers enlarges both the absolute width and the average layer height. An interface-based geometry-dependent iterative layer height model with correc-tive terms derived from the experimental results is proposed.